Tag Archives: exposure

Debunking Equivalence

What is equivalence? If you haven’t heard of this term used in photography before then don’t bother; you didn’t miss anything. (Part two is here)

If you are curious though, it simply means that different formats or sensor sizes require different settings in order to produce “the same” or equivalent images. Usually, equivalence proponents use the 35mm full frame sensor as the “reference standard”. For example, for a m43 sensor and full frame sensor to have the same angle of view (AoV), the m43 will have to use a 25mm lens and the full frame a 50mm lens because the m43 sensor is smaller; four times smaller to be exact. It doesn’t end there. Since a 25mm lens has a shorter focal length compared to a 50mm there will be differences in depth of field (DoF). The shorter 25mm will have to shoot at f/4 to get the same DoF as a 50mm at f/8.

There are other “parameters” involved in this “equivalence”. For more details, refer to this article in dpreview: http://www.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care

That dpreview article is funnily entitled “What is equivalence and why should I care”. Should you really care about equivalence? Most photographers don’t care about equivalence. Real photographers’ shooting techniques vary depending on the camera that they brought with them. Give a photographer a mobile phone and he will capture fantastic images without pretending that he is carrying a DSLR. I own a mobile phone, several point-and-shoot cameras, a few m43’s, an APS-C and full frame cameras. I know exactly what each one of them are capable of doing and I shoot accordingly. I don’t expect shallow DoF with my iPhone so every time I shoot portraits with it I need to be careful that the background does not distract from the main subject. Here is an example of how you can capture professional-looking portraits with a simple iPhone 3GS: https://fstoppers.com/editorial/iphone-fashion-shoot-lee-morris-6173.

Bottom line is, gear does not matter. If gear does not matter, equivalence does not matter.

But let’s not stop there. There is more to that equivalence article. To be precise, there are a lot of incorrect information in that article that are very misleading if you are not careful. The biggest misinformation that equivalence proponents spread in forums is that of “total light captured”. I will try to debunk equivalence in the next few paragraphs.

For the sake of example, let’s compare a m43 and a full frame (FF) sensor. By now you should already be aware that a FF sensor is four times larger than a m43 sensor. The m43 crop factor is therefore 2x. It follows that to shoot “the same image” we will have to use different lenses and use different f-stops like so:

m43: 25mm at f/5.6
FF: 50mm at f/11

This will result in the same AoV and DoF. Now what about the rest of the exposure triangle? This is where equivalence-fu starts becoming really stupid. The proponents insist that you could use the same shutter speed for both m43 and FF and still arrive at the same image. They insist that the same shutter speed must be used so that both images will result in the same “blurring” due to subject motion (ROFL!!!). The example above then becomes:

m43: 25mm, f/5.6, 1/125s
FF: 50mm, f/11, 1/125s

Wait, doesn’t that underexpose the FF image? Indeed it does. By two stops, to be exact! Didn’t I say it was stupid? In what world do two images, two stops apart, are considered “the same”? One is obviously darker. Much darker. Equivalence proponents must have something up their sleeves 🙂 You probably guessed it already. They say that you can bump up the ISO of the full frame shot so that it will be of the same brightness as the m43 shot! So now the example becomes:

m43: 25mm, f/5.6, 1/125s, ISO 100
FF: 50mm, f/11, 1/125s, ISO 400

Seriously?!!! Let’s be very clear about this. Bumping up the ISO does not increase light. ISO has absolutely no effect on exposure. Learn about that here. So why do you think that equivalence-fu proponents are suggesting that this ISO bump will make both images equivalent? Their reasoning is quite simple and stupid: because both sensors have gathered “the same total amount of light”!!! Recall that each stop of exposure means twice the amount of light. Since a m43 sensor is four times smaller than a FF sensor it means that underexposing the FF by two stops (4x amount of light) will still result in the same TOTAL light captured by each sensor. If that isn’t stupid then I don’t know what is.

Let’s discuss this further by using a simple experiment. Supposing that we have a m43 camera and we shoot a scene using a 25mm lens. We can produce a full frame equivalent image of the same scene with the same AoV using the same m43 camera by stitching four shots from a 50mm lens. Refer to the illustration below:

Screen Shot 2014-09-28 at 10.31.50 pm

As you can see, the smaller single shot image captured with a 25mm lens will look exactly the same as the larger stitched image which is equivalent to what a full frame sensor would have captured. The narrower AoV of the 50mm lens means that we need four shots stitched side by side to arrive at the same AoV as the 25mm shot. Again, this shows that a FF sensor is four times larger than a m43 sensor. Same AoV, same DoF but different image sizes due to the different sensor sizes.

Now let’s be stupid for a while and assume that equivalence is correct 🙂 In order for the single shot image and the stitched image to have the same total amount of captured light, we will have to underexpose by two stops, each of the four individual shots that we used to stitch the larger image. Since these four images are now much darker we will have to bump their ISO by two stops to arrive at the same brightness as the single shot image. At this point, we now have two “equivalent” images: the smaller, properly exposed m43 image and a larger full frame image that was produced by stitching four underexposed m43 shots.

Common sense will tell you that the larger stitched image is every bit inferior to the single shot image. Two stops inferior to be exact. If you sample a quarter chunk of that larger image it will always turn out much worse than the reference m43 shot. Take a quarter chunk from the top, bottom , sides, or center and every single one of them will look much much inferior to the original properly exposed m43 shot. We can therefore say that the larger image is inherently much inferior compared to the single shot m43 image. So how can equivalence proponents honestly say that the underexposed FF shot is “the same” as a properly exposed m43 shot? You don’t need half a brain to realise that this is plainly stupid.

The stupidity does not stop here though. The equivalence-fu followers have something else to support their “theory”. They suggest that if you print or view the smaller properly exposed m43 image and the larger severely underexposed FF image at the same size, they will look exactly the same. Well maybe they would look the same up to a certain extent. Recall that when you view or print an image at a smaller size than its original size then the effects of downsampling will take effect and will result in a lesser perceived noise: https://dtmateojr.wordpress.com/2014/05/19/megapixel-hallucinations/. This, however, has absolutely got nothing to do with light gathering. As we have shown in our example, the underexposed FF image is much much darker than the reference m43 image if it were not for the ISO bump. Equivalence proponents are using image size to circumvent the destructive effects of underexposure and they think that image size and light are one and the same. Image size has got nothing to do with light. A 41Mp Nokia phone camera has a larger image size compared to a full frame 36Mp D800 although the former has much much lesser total amount of light captured. This is why if you are not careful these equivalence-fu “photographers” will easily mislead you.

Let’s take this circus show to a higher level. Assume that total light and image size are equivalent and related. In that case, we could, in a sense NOT increase the ISO of the underexposed full frame image but instead downsample it to the same size as the m43 image and they should result in the same brightness, right? Simply because the same total amount of light has now been projected into the same image area which should result in the same exposure (total light over total area). But we know that this doesn’t work because downsampling or upsampling has no relationship to total light and that is why the downsampled FF image remains two stops darker. So how could equivalence proponents honestly equate total light and image size? :-O

So now we know that equivalence-fu relies on resampling to work around underexposure. Does this always work? No, it doesn’t. If you recall the discussion in the “Understanding Exposure” article that was linked above, bumping up the ISO does not increase light. It only increases gain. The analogy was that of the process of boiling water. Increasing ISO is like boiling water. Boiling pushes water to the top of the container but it does not increase the amount of water. If you underexpose, you will come to a point where there is no more light being captured. It’s like a container with no water. Bumping the ISO or boiling a container that does not contain water does absolutely nothing. Image noise is more pronounced in darker areas. Underexposure will only worsen the noise in those darker areas. When you have no signal, there is nothing to resample. Downsampling will not always save you.

The nasty effects of bumping up the ISO can not be ignored. Increasing the ISO will also result in hot pixels, banding and other nasty artifacts. Why do you think are cameras limited by how high you can set the ISO sensitivity? Why can’t we not bump the ISO indefinitely? Because the truth is, high ISO sucks regardless of sensor size. Imagine an ISO 6400 shot from a m43 Olympus E-M5 compared to an ISO 25600 shot from a full frame Nikon D800. How much worse does it get if you now compare a point-and-shoot camera with 5x crop factor to that D800. Five stops underexposure is A LOT and really bad. I mean really, try underexposing a night shot on your D800 by 5 stops then bump it up in Photoshop. Crash and burn baby!

If you think that’s bad then consider shooting with slide film. How big is a sheet of film for a 8×10 view camera compared to a measly 35mm camera? For the sake of argument let’s just say that the size difference is 5x. Do you really believe that if I shoot Fuji Velvia on 35mm and then I underexpose Velvia on the 8×10 camera by five stops and push it during development that the images will look “the same”? If this was negative film then maybe you can get away with it but don’t even attempt that kind of circus act with slide film. Slide film is very unforgiving when it comes to exposure. Five stops is almost the entire usable dynamic range of slide film!!! If a photographic “theory” fails miserably with film then that “theory” is simply wrong. In the case of equivalence, it’s bullshit, plain and simple.

So to answer that dpreview article’s question: “should you care about equivalence?”. Not if it’s wrong and stupid.

Update:

I can’t believe that people keep on spreading this nonsense. Here’s another funny equivalence-fu fauxtographer: equivalence for embeciles

Examine his illustration on the effect of different apertures f/8 and f/4. He is totally oblivious to the effect of focal length on light intensity. Note that although f/8 and f/4 here have the same physical aperture size, the longer focal length of the f/8 lens causes the light to be projected much wider into the sensor. The net effect is that each sensel behind the longer f/8 lens receives much lesser number of photons than the sensels behind the shorter f/4 lens. The result is underexposure which is seen as a darker image. Two stops (or 4x light) of underexposure to be exact. This obviously corresponds to noisier sensel output and therefore noisier image.

How can two images with different exposures be equivalent?! Such an idiotic explanation is the result of the epic failure to understand very basic photography. Exposure is totally independent of sensor size. The same f-stop results in the same total number of photons per sensel regardless of imaging format. Always. Same f-stop means same exposure meaning the same brightness.

Blinded By Light

The full frame protagonists are at it again. It’s the same stupid argument. Larger sensor means more TOTAL light gathered therefore lesser noise. Stop the bullshit. Please!!!

In fairness, it’s quite easy to be mislead by this kind of misinformation. If noise is inversely proportional to the amount of gathered light then it makes sense that a larger sensor would result in cleaner photos. Unfortunately, just looking at the total amount gathered light is being very short-sighted. It does not give us the whole picture (no pun intended).

Allow me to explain it again for the nth time. But before that, please read the following articles because they explain this concept in greater detail.

1. https://dtmateojr.wordpress.com/2014/02/28/understand-your-lens-part-3/ — Concentrate on understanding the effect of focal length on light intensity because a lot of people tend to ignore this bit. They are too preoccupied with just the aperture opening maybe because they are more familiar with “fast” lenses without even understanding what “fast” really means.

2. https://dtmateojr.wordpress.com/2014/03/08/debunking-the-myth-of-full-frame-superiority/ — If there is one thing that you’d want to fully understand here, make it the “thought experiment” on dividing a full frame sensor which also explains how shutter curtains work.

3. https://dtmateojr.wordpress.com/2014/06/10/debunking-the-myth-of-full-frame-superiority-part-2/ — This is a good counter-argument to the fact that no two digital sensors are exactly the same even if they are of the same type. A D7000 sensor for example is almost every bit the same as the D800 sensor but because of the improved processing the latter may produce better photos. And so I used film as an example because the same film emulsion will always behave the same way regardless of format (size).

4. https://dtmateojr.wordpress.com/2014/05/19/megapixel-hallucinations/ — Some full frame protagonists insist on comparing ENLARGED APS-C images to full frame equivalents in terms of noise. Of course an enlarged APS-C photo will, for the lack of a better word, enlarge everything including noise. This article debunks that by showing the MATH behind resampling as well as showing samples of real SNR measurements of APS-C and full frame sensors.

5. https://dtmateojr.wordpress.com/2014/04/21/rain-can-teach-us-photography/ — explains what happens in a sensor and why PIXEL size and NOT sensor size matters in greater detail.

6. https://dtmateojr.wordpress.com/2014/05/09/understanding-exposure/ — are for the equivalence clowns who think that they could get away with the bullshit by manipulating ISO. In short, you can’t.

Now if after reading those articles you still need a bigger cluebat then read on…

The biggest mistake that full frame protagonists make is that they equate a sensor to a solar panel. In a solar panel, total light gathered is everything. In a solar panel, every “sensor” contributes to the total energy produced. Of course the bigger the better. Photography though is far from being like a solar panel. Camera sensor pixels are independent of each other. That’s why within an image you will encounter darker parts that are more noisy and blown up parts that have been saturated by light. Each individual pixel receives its own independent number of photons. Pixels can’t share their photons with other pixels. Well sometimes adjacent pixels do “share” photons but this is an undesirable effect called “sensor bloom”. You can see why looking at noise as a result of the total light gathered is wrong. Noise should be examined at the pixel level because this ultimately defines the efficiency of your sensor.

While it is true that a larger sensor gathers more light compared to an APS-C or M43 for the same exposure by virtue of the larger area, this argument is not photographically sound. Photographic exposure is all about LIGHT PER UNIT AREA and not just total light. Saturating a pixel only requires a fixed number of photons. Anything more than that is just wasted light because as soon as a pixel clips then “no data” is presented for processing into an image. An APS-C sensor for example requires half the total amount of light required for a full frame sensor. If you force the same amount of light to both a full frame and APS-C then the latter will oversaturate, i.e. overexpose. It’s like pouring two liters of water into a one liter container. It does not make sense. It is photographically disastrous and plainly stupid. Therefore you get the same noise-free image in an APS-C for half the total amount of light hitting the sensor. Again, you get the same noise-FREE image for HALF the TOTAL amount of light. Again, it’s all about LIGHT PER UNIT AREA and NEVER just total amount of light gathered. It’s all about light intensity.

A smaller area requires lesser incident light. A smaller sensor requires a smaller lens-projected image circle. Smaller image circle is what defines a “crop” sensor or crop lens (e.g. Canon EF vs EFS lenses or Nikon FX vs DX lenses). You crop a full frame image circle just enough to illuminate a smaller sensor. Makes sense?

Unfortunately, there are those that remain blind and they resort to other stupid arguments such as printing at the same size or enlarging a cropped image. Of course a larger sensor is capable of larger prints but this has got nothing to do with light. But let’s be stupid for a minute and assume that a cleaner print is the result of more light gathered during exposure. What happens then if you print at a smaller size? Did you just throw away the light? If not, then where did the light go? If print size has got anything remotely related to light then projecting the same amount of light into a smaller print is like pouring two liters of water into a one liter container so we expect the smaller print to be overexposed, right? But it doesn’t. Because print size has got nothing to do with light and therefore has got nothing to do with noise. The apparent increase in noise when you enlarge a print is NOT the effect of light but the effect of resampling (refer to megapixel hallucination article), i.e. resolution.

In conclusion, total amount of light is just half the truth. The other half is sensor area. Combining both, we get light per unit area otherwise known as photographic exposure. Exposure is what ultimately dictates noise. Smaller area requires lesser light therefore the same exposure results in the same noise profile for different sensor sizes of the same type.

I hope this is the last time I will ever write about this topic. It’s getting long in the tooth and very boring really.

I promise to write a happier article next time. Really. I promise that. 

The First 100

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Welcome to my 100th post!

To be honest, I didn’t expect to get this far with blogging. I have attempted to start writing in several other sites before but I never really got motivated to move forward with them. I am a computer geek by profession and I spend most of my day in front of a computer managing Linux servers scattered all over the world. In my spare time I customise Linux distributions for my own workstation needs. I’m not really sure what kept me writing this time around. It’s probably because I decided to cover photography instead of the usual computer-related topics.

I’m relatively new to photography. I formally started back in April of 2009. I still remember my first photoshoot session. Me and a friend started driving at 4AM to get to our destination before sunrise. It was then that I learned that to capture a good shot you will have to make some sacrifices, like sleep for example. I remember shooting every weekend for several months from 5-9AM and going home with a thousand frames with no keepers. I didn’t really understand photography back then. I mean, I still don’t understand most of it now but back then I was practically clueless. The most important thing that happened for me was getting hooked in this hobby and I have been shooting ever since.

At this point I would like to thank the beginners in photography for asking those (sometimes silly) questions in forums. They were my sources of ideas for articles. A special thanks as well to those who keep on spreading nonsense — you inspire me to write some more.

Some of you might notice that a few of my articles are quite controversial. The most popular ones were those that attempted to debunk the myth of full frame superiority namely:

1. https://dtmateojr.wordpress.com/2014/05/19/megapixel-hallucinations/
2. https://dtmateojr.wordpress.com/2014/03/08/debunking-the-myth-of-full-frame-superiority/
3. https://dtmateojr.wordpress.com/2014/06/10/debunking-the-myth-of-full-frame-superiority-part-2/

I feel that it is my duty to educate those who are new to photography. The biggest problem at the moment is that photography has become a contest of who has got the largest camera and fastest lens. Beginners feel inadequate just because they don’t own a full frame or a prime lens. It’s not just gear but starters are also made to feel incapable just because they are shooting in auto mode or in JPEG. Armchair photographers have set up artificial walls that prevent beginners from enjoying and moving forward with photography: Your small camera isn’t good enough; Learn to shoot in manual mode; You will not get far with only a kit lens. No wonder only a very few of them continue with their hobby. This kind of bullshit has to stop.

I have chosen NOT to write about topics that everyone will just agree with. If everyone will just agree with me then what’s the point in writing? You might as well go to any forum and drink the kool aid. Instead, I write about the advantages of smaller cameras, your cheap kit lens, why you might want to shoot in JPEG or why you should learn to shoot instead of dealing with a lot of nonsense.

There are times when I feel like writing something highly technical but in a simplified way. My background is in Physics and I understand that not everyone is comfortable with numbers. The topics that I covered were not the usual stuff that everyone knows but instead I discussed the most commonly misunderstood concepts that most people think they already know by heart such as resolution and exposure.

I would also like to apologise to those who felt uncomfortable with the tone of my articles. Rest assured that they were not aimed at you unless you were one of the idiots in forums who called me stupid for using physics and math to prove that you are a moron for believing and spreading that bullshit. You know who you are and it feels good to be vindicated. Thanks for the free publicity.

If you got this far, thanks for reading. I can’t wait to write some more. I actually have a list of topics in the queue already. I’ll talk about the camera that I recently won in the Olympus Asia-Oceania Grand Prix photo contest in my next post so stay tuned.

🙂

Pros and Wonky Exposures

Back when I was just starting to get serious with photography, I always checked the EXIF data of the photos that I found to be interesting. For me, the EXIF data was a learning tool. I thought that knowing what focal length and exposure to use to achieve a particular shot would give me a reference point in case I wanted to create a similar image later on.
 
 Fast forward a few years later, I realized that EXIF data is quite useless. I have learned that the images that I tend to appreciate have very little resemblance to the original shot that was captured on camera. Most photos that are above average are usually heavily post-processed. I do this to my own images as well. It is not uncommon for me to intentionally underexpose the shot in order to save the highlights and then push the shadows later in post. If a beginner was to follow my EXIF data, it would give him the wrong impression of the shot. Unless the viewer was at the scene of the shot, an EXIF data does not really tell how bright the ambient light was. You will have to rely on other external data such as the time it was taken, the location and the weather to make sense of it. It would be even worse if the final image was a composite of multiple bracketed exposures because the EXIF data would be totally misleading.
 
 I can’t help but notice that some photographers will include their exposure settings when describing their shots. Unless the images are totally unprocessed, I can’t find any relevance at all. In fact, there are times when I even question whether the photographer actually knew what he was doing. Consider this shot for example (taken from Australian Photography magazine)
 
 
 
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The exposure reads 1/320s, f/6.3, ISO 800, +3.3EV. If this was shot in aperture priority mode, why f/6.3? Why not something more exact like f/5.6 or f/8? If it was shot in shutter priority mode, why 1/320s? That is not even “flash friendly” (1/250s). The most confusing part is the +3.3EV exposure compensation. If you have to compensate this much then you might as well shoot in full manual mode. I’m not questioning the result but the exposure info is hardly useful. In fact, it is confusing even to an experienced photographer.
 
 This is not an isolated case. The winning photojournalism photos are littered with the same wonky exposures. One of them read 24mm, f/1.4, 1/8000, ISO 50!!! You can see that the photographer forced the shallow depth of field cliche of f/1.4 because it pushed the camera to its maximum shutter speed and the sensitivity was intentionally set to the wonky fake low ISO. Nevertheless, the shot was a winner. And this is where the problem lies. A beginner would think that this kind of circus act is proper photography. It’s not.
 
 Let this be a warning. Unless you are shown a completely unedited shot, do not take the EXIF data as gospel. Even in “true to life” photojournalistic shots, EXIF data should not be swallowed just like that. Think for yourself.

Understanding Exposure

This is a continuation of my previous post on where I used the analogy of a rain gauge (Rain Can Teach Us Photography) to understand photographic exposure. Here we dig deeper into understanding what photographic exposure really means in terms of real photography. 

You might have heard of the concept of exposure triangle. This concept explains the interplay between three independent aspects of photographic exposure namely:

1. f-stop

2. shutter speed

3. ISO sensitivity

Item #1 is more often incorrectly referred to as aperture. Although f-stop involves aperture, saying that f-stop is equivalent to aperture is photographically wrong because aperture alone totally ignores the effect of focal length in the intensity or amount of light that hits the sensor. I have covered this in detail in this post: Understanding Your Lens (Part 3). Please read that post if you have difficulty understanding this concept.

The main reason that I am discussing this supposedly understood-by-all-photographers concept is because it’s actually misunderstood by a lot of photographers – myself included until after reading and conducting experiments. Before I start, I would like to acknowledge a friend, Dan Bridges, for introducing and helping me understand this concept. It is not really a difficult concept to comprehend but it will surely change the way you think because we are accustomed to thinking in terms of the exposure triangle.

Let me start by saying that the exposure triangle is not entirely correct. Yes, you read that right. In fact, when you talk about exposure it’s really just the first two items: f-stop and shutter speed. ISO is not really a part of exposure and you will soon understand why … hopefully.

Begin by understanding that the amount of light in the scene that you are trying to capture is fairly constant throughout the entire exposure. Unless you are doing very long exposures in a disco bar or covering a concert gig, the ambient light is practically unchanging. Therefore whatever light that comes into the sensor chamber is basically controlled by your chosen f-stop and shutter speed.

Let me repeat that: the amount of light hitting the sensor is only affected by f-stop and shutter speed.

So why is ISO sensitivity not part of the equation? Because for a particular camera, ISO sensitivity is constant. You do NOT have any control of it. Surprised?

The immediate reaction is, “of course I can control my ISO”. Yes, cameras let you change the ISO but you are not really changing the ISO. It’s not real. You are lead into thinking that you are changing the ISO when in fact you are not. What you are changing is not the ISO sensitivity of your sensor but the brightness of the image. What you are changing is technically the gain.

The ISO sensitivity of any given camera is FIXED at manufacturing time. This is called the native or base ISO. It can not be modified at all. It is very important then that you know the base ISO of your camera. Read your camera’s manual. The Nikon D700 for example has a base ISO of 200 while the D800 has a base ISO of 100. We say that the D700’s sensor is more sensitive than the D800’s. If you think of sensors as water containers, differences in base ISO is like differences in the height of the containers. Same opening size but different heights. A sensor with higher base ISO is like a shallower container. It means that an ISO 200 container will fill up quicker than an ISO 100 container. Here’s an illustration:

Image

Allow me explain further. If you pour water at the same rate into two containers where the only thing different between the containers is their height, they will obviously have the same water level after any given time. Photographically speaking, same water level means same light level meaning same exposure. However, if you continue pouring water at the same rate, there will come a time when the shallower container will overflow and then water will start spilling for that container. As we have said, a higher ISO is like a shallower container. The sensor with higher base ISO will overexpose quicker compared to a sensor with lower base ISO. Water (light) will spill more quickly for the shallower container (higher base ISO). This means that if for a given ambient light, f5.6 at 1/125s is just enough to fill up an ISO 100 sensor to its brim, the same f5.6 at 1/125s will overexpose the ISO 200 sensor causing light to spill somewhere else (blown highlights).

As you can see, exposure is really NOT about the ISO but the amount of light that gets into the sensor. The base ISO is more of a warning label telling you not to overexpose your sensor or else light will start to spill. If a water container says it has a 100ml capacity, you would not want to pour 200ml of water into it. Makes sense?

Recall that base ISO is fixed and it can NOT be modified. It follows that the only way to control exposure is by f-stop (container opening) and shutter speed (total time that you are pouring water into the container).

Now let’s try to understand brightness. This is different from exposure. The definition of brightness is as camera-specific as that of base ISO. For the sake of simplicity, let’s say that an empty sensor produces a pure black image and a completely filled up sensor produces a pure white image. Since different sensors with different base ISOs fill up at different rates, it follows that they have different definitions of what is black or what is white.

Now here is an interesting outcome: Supposing that f5.6 at 1s is just enough to fill an ISO 200 sensor. It means that for that sensor, f5.6 at 1s produces a pure white image. That same f5.6 at 1s though is not enough to completely fill up an ISO 100 sensor. Therefore the same exposure will produce a slightly darker image for the ISO 100 sensor simply because the sensor is not completely full. Note that they have exactly the same amount of gathered light but they are producing totally different images. To produce the same pure white image, the ISO 100 sensor will have to be exposed longer at 2s for the same f-stop of f5.6.

Here’s another interesting fact: You can actually make the ISO 100 sensor in the example above produce a pure white image at the same f5.6 at 1s exposure. How? By artificially filling up the sensor until it’s full by adding “something”. If light in a sensor is like water in a container, you can make the water reach the top by boiling it. The amount of water will be the same but the act of boiling it has made it fill the container to its brim (and possibly spilling some of it). This “act of boiling water” is what happens when you increase the ISO in camera.

Increasing the ISO in camera does NOT add light to the sensor at all. It does not increase the exposure. It only artificially fills up the sensor with something. It boosts the signal. Unfortunately boosting the signal boosts everything including noise. The problem with increasing the ISO is not the act of boosting the signal itself. The main problem is that sensors have inherent noise in them already – signal or no signal. In darker areas where there is no light (signal), noise is still present. That is why if you boost the darker areas of an image, what you are boosting is just noise because there is no signal. Noise is more pronounced in darker areas of an image at high ISOs. This is why you do not test the high ISO performance of your camera in good light. That’s cheating. You should test high ISO in low light.

And now we finally arrive at an interesting consequence. Supposing that you are shooting in low light and you have chosen ISO 1600 so that you can hand hold your camera at a shutter speed of 1/125s at f5.6. Since exposure is only affected by f-stop and shutter speed, you can actually shoot at your base ISO, say, ISO 200 at the same 1/125s at f5.6 without affecting the final image. Of course when you look behind your camera’s LCD, the image will be very dark and you won’t probably see anything. However, when you get to your computer, you can use the exposure slider in Lightroom or Photoshop to boost the signal and arrive at the same image as the camera-boosted ISO 1600 image. The reason this is possible is because the exposure is the same. It’s still f5.6 at 1/125s. You either choose to boost the signal in camera by increasing the ISO or shoot at base ISO and boost the signal later in the computer. The advantage of doing this boosting in the computer is that modern software are smart enough not to boost highlights that are near clipping point. Your camera is not that smart and it will boost everything thus causing blown out highlights.

Disclaimer: that last paragraph is not always true. Some sensors behave differently. Sensors are actually more complicated than just a simple container so experiment with your camera.

This discussion won’t be complete without covering fake low ISOs that are in every camera. For example, the Nikon D700 has a base ISO of 200 but it also has Lo 1 which is equivalent to ISO 100. This lower fake ISO allows you to shoot at longer exposures. Since we know that the sensor ISO is fixed, fake low ISOs won’t actually gain you anything. The longer exposures will only cause areas of highlights to blow up. This is no different to applying the same ISO 100 exposure, say, f5.6 at 1/125s to an ISO 200 sensor. The ISO 200 sensor will be overexposed by a stop. So the same thing happens when you use a lower fake ISO and increase the exposure. Your sensor will be effectively overexposed.

To summarize everything:

1. Exposure is only affected by f-stop and shutter speed.

2. A camera’s base ISO is more of a warning label saying do not exceed your exposure beyond this point. It is a fixed value.

3. Increasing the ISO in camera only boosts the brightness of the resulting image. It does not increase the sensitivity of your sensor. With some cameras, you are better off boosting the image later using a photo editing program.

4. Fake low ISOs will do you no good. If you need a longer exposure then use a longer exposure using your base ISO. The consequences will be the same: blown highlights.

Being One With Your Camera

I have written several topics in the past that have stirred more than just a bit of (heated) discussions in photography forums. Zoom vs prime, JPG vs RAW, manual mode vs auto, this brand vs that brand … the list goes on. Nobody wins. The reason was quite simple: I had my own choices and they had theirs.

And this brings me to the topic of being one with your camera. There are lots of cameras and lenses to choose from. The most important thing is that you should use the combination that will give you the most potential. The equipment should not get in the way of photography. It should do as you wanted it to do. There is no perfect camera or lens though so it is very important that you are truly familiar with your gear. Just because it’s the best in terms of specification does not mean it will work for you.

Let me give you an example and I have posted about this in the past. I dared to compare my full frame Nikon D700 and my not-so-famous Pentax K5 in this post. My choice wasn’t about the perceived superiority of the D700 because it is full frame and has hundreds of lenses to choose from but the fact that the K5 did exactly as I would have expected in a landscape camera. There is no point in arguing about image quality or some other magical ingredient of a particular camera when you are constantly wrestling with it. The camera should work for you. Not you working hard on your camera.

Allow me to give a more specific example of why familiarity with the equipment is very important. I have been doing a bit of street photography lately. Admittedly, this area of photography is something that I am not experienced with but I’m trying really hard to make sense of it. My camera of choice is my Olympus E-M5 because it is small which means I can bring it with me every day to work. When I have spare time during lunch break I go out and shoot. I use aperture priority mode — again, a deliberate choice. I refuse to use the macho manual mode unless necessary. I set the E-M5 to its native ISO 200 and set my aperture to f5.6. Why these settings you may ask. When I’m out shooting on the streets during lunch break the range of light intensity can only vary by 4 stops at most. Under very bright sunlight, the meter reading would give me a shutter speed of 1/2000s which is well within the limit of the E-M5’s max speed of 1/4000s. When the subject is under the shadows of buildings the recommended aperture is usually f4 but since I’m at f5.6 then my shutter speed would drop to 1/125s which is still a very comfortable speed for handheld shots and fast enough to capture the movement of people walking about. Notice that we have not really discussed the equipment yet. I have basically provided a starting point from which adjustments can take place. These settings are ideal when the light is good. It will change significantly even with just a simple cloud cover. When the sun is covered by clouds f4 will not be enough when the subject is under the shade. If I stay at f5.6 my shutter speed could drop to 1/60s or even less. I have two choices: open up to f4 or bump up the ISO to maintain a comfortable shutter speed. With my E-M5, this is very easy. I have customised my buttons in such a way that I could change my ISO without even looking at my camera. Press a button and one turn to the right brings me to ISO 400 all with one hand. I also know that two clicks counterclockwise with the front dial would bring me to f4. Now coming out from a shady area into the open with the sun still covered by clouds I know that I can safely compensate the exposure by +1EV without blowing up the highlights by turning the rear dial twice to the right. I can do all of these without the need to look at my camera’s LCD. I can concentrate on looking at potential targets instead of fumbling with my equipment.

The whole point of the above example is that by knowing your exposure values and by familiarising yourself with your camera you can become a more effective photographer. Just to provide some sort of example on why the wrong choice of camera could become problematic in the same situation: I try to avoid using my Nikon D700 in street photography for several reasons. Firstly, the D700’s exposure compensation is stupidly in reverse. Going left is positive and going right is negative — exactly the opposite of what a sane camera should be. You can reverse this behaviour in the menu but then that reverses everything which means if I turn the front dial counterclockwise the aperture closes instead of opening up. Not only that. Changing the ISO requires that I use both hands! When changing modes, you have 50/50 chances of getting it right because there is no mode dial but a button that needs to be pushed and a front dial that needs to be turned. So if you are in M mode and you want to go to A mode you will have to press a button and you won’t have any idea whether to turn the front dial left or right to get to your target mode. Going back from A to M is the same crap. If you miss the turn it means you will have to turn twice in the opposite direction to get to your intended mode. I have owned my D700 for more than three years now but I still have not mastered this very simple thing. It has always been a constant hit-or-miss that really annoys me.

Another important thing is choice of focal length. My favourite is 35mm in full frame or 24mm in APS-C or 17mm in m43. With this focal length I know exactly how my subject fits in the frame without even looking at the viewfinder. A lot of photographers recommend the 50mm full frame normal lens because they say it’s has the same field of view as the human eye. I can’t relate to this. For me, normal means 35mm. I find that 50mm is too tight and more suited to portraiture instead of daily walkabout type of shooting. I really like this focal length because it allows me to shoot people, architecture and landscape.

My point is, don’t just follow what you read in forums. Find your own thing.

N00bism #3

Hello world! This the third post of the N00bism series. I hope that the previous articles made you think about your own approach to photography. As I have mentioned before, this series aims to discuss the common mistakes beginners, and to some extent, even experienced photographers fall into. These are the same issues that I have experienced and/or avoided and have observed in my constant interactions with photographers of different levels of expertise.

Without further ado, let me discuss “premature manual mode”.

I have already written an article about this macho manual mode, or M mode as most photographers call it. It’s ok if you shoot in “M mode only” but puhleeze, don’t brag about it. It’s not rocket science. You do not have to tell the world about it because those who actually know how to use it will find your bragging quite underwhelming or laughable.

Those of you who are just starting with this expensive hobby should avoid using M mode. Trust me. I have been there. Allow me to explain:

Firstly, you bought that very expensive camera for what? It’s expensive because it is intelligent enough to do most of the work for you. You are wasting your money if you do not put it to good use. It has full automatic mode for a reason. Even the most expensive of cameras have auto modes. Auto modes make your life easier so you can concentrate on things that matter.

For newbies, what matters most is making the shot. You can have the most perfectly exposed shot but if your composition sucks then your photo sucks. Period. Why burden yourself with the exposure when you can’t even get your horizon straight? Why fiddle with those buttons when your shot is so hopelessly cluttered? Why shoot in M when you do not even understand exposure in the first place?!!!

Do yourself a favour. Use that green square mode and learn about composition before anything else. If you can’t help touching those buttons then leave your multi-hundred dollar DSLR and use your mobile phone instead. Yes, even if the “image quality” is inferior. A clean, crisp, 36Mp crappy shot is still a crappy shot.

So when should you start using the M mode? If you think that a better exposure will improve a good shot. It follows that you know what a good shot is. It also follows that you know what exposure is. If you can’t get a good shot with your mobile phone, your DSLR won’t help either. Because a good shot does not depend on what camera you use. In fact, more complicated cameras would probably hinder you from making a good shot.

I won’t cover composition here. It’s not something that you learn by reading. Yes, there are pointers like rule of thirds. Google them.

I will skip to the topic of exposure because that’s all this crazy M mode does anyway. Sorry but I won’t even discuss the exposure triangle here. If you do not understand that concept then you should not even be thinking about M mode. There are millions of web articles that discuss it and I won’t bother repeating them.

How do you learn exposure? By understanding light. Understand that during high noon on a very clear day, you will have the greatest intensity of light that you would normally encounter. I said normally because you might want to shoot directly at the sun or capture an exploding atomic bomb. Anything else would just be varying intensities of lower magnitude. This high noon light is often called “sunny f16”. It simply means that the correct exposure for a subject under bright sunlight is f16, 1/ISO for a given ISO sensitivity. For example: f16, 1/100 at ISO 100. We usually “round off” the shutter speed to the nearest “whole stop”, which is 1/125 for the above example. An example of light with lower intensity is when your subject is hiding under a shade to avoid the harsh sunlight. In this instance, light intensity drops by at least 4 stops so your exposure would be f4, 1/125 at ISO 100. Sometimes I give it f2.8 just to be safe.

It’s not enough that you know the different light intensities. You should understand contrast as well. In the above example, if you want the subject in the shade to be properly exposed then everything outside that is lit by the sun will render as white. If you want to properly expose what’s outside then your subject will be barely visible under the shadows. In this example, no amount of screwing around with M mode will help you. The argumentative folks will probably say, yeah shoot at f8 then pull the highlights and push the shadows in Photoshop. Whatever.

You see that it’s not enough that you know shutter speed and aperture and ISO to warrant the use of M mode. Because if you do not undertand light you will end up screwing around with those knobs until your camera’s LCD tells you that you have lined up the exposure slider dead in the center. You are basically wasting your energy following what the camera is telling you. M mode has become the automatic mode for stupid people. M as in moron mode. Shoot in full auto instead.

So beginners, please learn to compose first before confusing your brain even more with M mode. And experts, there’s no need to brag about it especially if you are just lining up the sliders.