Tag Archives: d700

Understanding the Effects of Diffraction

This post is a continuation of the previous article that I wrote about resolution and diffraction. I highly suggest that you read that one first so that you will gain a basic understanding of these concepts.

One thing that a lot of people still fail to understand is the absolute effect of diffraction on image resolution. A common argument of buying a higher megapixel camera is that it would “always” resolve more detail than a lower megapixel camera. That is true but only until you hit the diffraction limit. For example, a full frame camera shot at f/16 will not resolve any detail higher than 8Mp. That is, a 36Mp D800 will not give more details compared to a 12Mp D700 when both are shot at f/16. They both will have an effective resolution of 8Mp only.

To explain this, let us consider a very simple analogy. Notice that when you are driving at night in complete darkness, it is very difficult to distinguish if an incoming vehicle is a small car or a big truck if you were to judge only by their headlights. This is because the apparent separation between the left and right headlights is very dependent on the distance of the vehicle from your position. The headlights seem to look larger and closer together the farther the vehicle is from you. If the vehicle is far enough, both headlights will seem to merge as if there is just one light and you would think it’s a bike instead of a car. The reason is simple: light spreads. Both left and right headlights spread until they seem to merge and by then they become indistinguishable from each other. Diffraction is the same. Diffraction spreads light and you lose the details. Therefore it doesn’t matter if you have two eyes or eight eyes like a spider, you still won’t be able to distinguish two separate headlights if the incoming vehicle is very far. In this case, eight eyes are no better than two eyes. Both sets of eyes still see only one headlight not two. Think of the “number of eyes” as your sensor resolution. It does not matter if you have 8Mp or 2Mp, both cameras will detect only one headlight. Did the 8Mp lose resolution? No. It remained a 8Mp sensor. Did it manage to detect two headlights? No. Therefore in our example, a 8Mp is no better than 2Mp in resolving the number of headlights.

The point is that diffraction destroys details. When there is nothing to resolve, sensor resolution does not matter. Supposing that you have two lines that are very close together, diffraction will spread both lines such that they will appear to merge as if they are just one big line. If you only have one line to resolve it does not matter if you have a 2Mp camera or a 100Mp camera, both will detect only one line. The 100Mp camera will of course have more samples of that single line but it is still just one line. Diffraction does not affect sensor resolving power but it affects how the subject is presented to the sensor. Diffraction blurs the subject in such a way that it limits what the sensor can fully detect.

With that in mind, let us look at practical examples. For a full frame sensor, diffraction at f/8 is enough to blur the subject such that anything higher than approximately 30Mp will not resolve any more details. For each stop, the effective resolution drops by half so at f/11 the limit is 15Mp and at f/16 it’s 8Mp and at f/22 a measly 4Mp. These numbers are just approximations and assume that you have a perfect lens. The reality is much lower than those values.

How about smaller sensors like APS-C or m43? The decrease in resolution is proportional to the crop factor. So an APS-C shot at f/8 will only have a maximum effective resolution of 15Mp while m43 will have 8Mp and so on.

Here are MTF graphs for a Nikon 50/1.4 lens comparing a 16Mp D7000 (crop sensor) with a 36Mp D800 (full frame) at f/5.6 and f/16 respectively. Notice that the resolution at those settings are very similar.

So what are the implications? If you are a landscape photographer with a 36Mp Nikon D800 and you shoot at f/8 or f/11 or maybe f/16 to gain enough depth of field you are basically wasting disk space. At f/8, your 36Mp sensor is no better than a 30Mp sensor. At f/11 it’s no better than a 16Mp D4. At f/16 it is no better than a very old 12Mp D700. So a 36Mp sensor shot at small f-stops is not able to capture enough details and yet the image size remains the same and consumes 36Mp of disk space. If you shoot at f/16 for example, you are better off shooting with a 12Mp D700. If you want to print as big as a 36Mp camera then upsize your 12Mp image in Photoshop to an equivalent of a 36Mp image. Of course the upsized image will not gain any details but it doesn’t matter because the 36Mp hasn’t resolved any more details anyway.

A related analogy is that of scanning photos. Good prints are usually done at 300dpi. When scanning photos, it does not make sense if you scan higher than that because you won’t gain anything. Scanners are capable of 4800dpi or even 7200dpi and maybe higher. If you scan a print at 7200dpi you will get a really huge image but with no more detail than when you scanned it at 4800dpi or lower. You could have just scanned it at 600dpi and you won’t notice any difference. The 7200dpi scan is a waste of time and disk space.

Another common argument is that a sensor with lots of megapixels allows more cropping possibilities. Again, that is true only if you are not diffraction limited. Otherwise you could just shoot with a lower Mp camera, upsize the image and then crop and it will make no difference in terms of details.

This is why I have absolutely no interest in the D800 and other insanely high Mp APS-C cameras like the D7100 and K-3 and A6000. I shoot mostly landscape. I stop down to f/11 and sometimes even to f/22. At those f-stops these cameras are just a waste of space, time and processing power. Again, a 36Mp full frame camera does not make sense unless you shoot mostly wide open at f/5.6 and wider. A 24Mp APS-C is stupid unless you mostly shoot at f/5.6 and wider. Manufacturers keep increasing sensor resolution instead of improving noise performance because most photographers are gullible. Megapixels sell.

Having said that, do not be afraid to shoot at smaller f-stops if the shot calls for it. Even 4Mp effective resolution is a lot if you print at reasonable sizes. And since most people never print at all, 4Mp for web viewing is GIGANTIC!

For a more comprehensive explanation of the effects of diffraction refer to this article: http://www.luminous-landscape.com/tutorials/resolution.shtml

Shoot and shop wisely. 🙂

Snowy Pilgrimage 2012 Update

I thought I would be able to update my blog throughout the course of the snowy trip. It turned out to be the most different among the trips I had. Not only did I lose access to the internet most of the week but the type of subjects and shooting opportunities were very different as well. There were no planned shots at all. I just aimed and shot whenever I got the chance. It was a run-and-gun type thing.

I brought my D700 with me because of the larger buttons that are easier to press in the cold. I also managed to bring my Olympus E-P3 by accident because it was inside my work bag together with my laptop. As it turned out, the E-P3 became my most valuable camera while the D700 stayed inside the car trunk!!! I would say that this trip was like a test drive of the E-P3.

For the mean time, here’s a shot I took with my iPhone in East Jindabyne:

I will post photos and stories when I get back to Brisbane tomorrow after a 12-hour drive.

— from my iPhone

Megapixel Wars Resurrected

Back when digital photography was in its infancy, people were after the camera that had the most megapixel. Resolution was king. And rightly so. Digital photos looked crap when printed large especially when compared to the enlargements made from film. It wasn’t until sensors hit the 6Mp mark that digital photography became a viable alternative to 35mm film photography.

But it didn’t stop there. Megapixels kept climbing. Even point-and-shoot cameras with their tiny sensors reached a whooping 14Mp and that trend continued until the present. Megapixels were the easiest way to trick customers into buying the latest model. People upgraded their 8Mp camera to 10Mp!!!

Now photographers have learned that megapixel isn’t everything. Even some camera manufacturers have learned their lesson. The Canon G10 with 14Mp was upgraded (or downgraded) to 10Mp with the release of the G11 and G12. The megapixel wars are slowly dying…up to a certain point (the latest Nikon D800 has 36Mp!!!).

You’d think that would silence the gear whores. Unfortunately, there’s a new kind of war that’s raging in the “photography” forums and it goes with the initials of “I.Q.”. I’m not talking about intelligence quotient but in fact, it’s actually a dumb war. IQ stands for “Image Quality”.

Image Quality. What exactly are they looking for? Let’s have a look at the “requirements”:

1) High ISO performance. If your new camera can’t produce clean images at ISO 6400 then it’s not good enough.

2) Sharpness. If it looks blurry at 200% zoom then it isn’t sharp enough.

3) Bokeh. Anything slower than f2.8 for zoom lenses or f1.4 for primes isn’t good enough.

4) Add more stupid requirements here.

The war has become uncontrollable and has grown n times!

Seriously, WTF people?!

Let’s tackle those 3 items one by one.

High ISO performance. This is my favorite. Back when real photographers shot with film, people didn’t complain about grain the size of boulders. Grain actually added character to the photograph. Weddings were at times shot with ISO 1600 film when the light dropped considerably. The unfortunate ones who brought only ISO 400 film had to push them during development which made the photos look more “interesting”.

Sharpness. I went to an exhibit of Henri Cartier-Bresson’s photographs and let me tell you that a lot of his photos were really blurry. But they were so awesome that you would never even pick on the picture quality. I was there dragging my jaw on the floor.

Bokeh. People buy these outrageously expensive, fast, heavy lenses. For what?! So you can shoot wide open at f1.4 and complain that you can’t get your focus right? They say it’s for shooting in low light. Yeah, that’s why you want that ISO 6400 as well right? Let me see, where can I find a place that “requires” f1.4 at ISO 6400? Hmmmm…. Uh, none?! Of course somebody out there will always manage to trap himself in a dark cave…everyday…and that makes the purchase fully and truly justifiable. If you really need to shoot in very dim light then use a tripod. You know, that cheap thing with three legs. But I’m sure a tripod isn’t good enough for them so let’s stop right there.

Measurebators will always find a reason to justify their purchase. Go find a pulitzer photograph and see if there’s any that meets the IQ requirements. I actually proposed this challenge to a measurebator and he gave me the photograph of the Afghan Girl that was captured by Steve McCurry. I had to stop myself from laughing inside the train. This guy probably thought that the photograph was captured by a digital Hassy or a Nikon D3s 🙂 I had to explain to him about 135 Kodachrome and told him to go get himself a 6Mp point-and-shoot camera if that was his reference for image quality.

Just for laughs, somebody posted HCB’s photo of the cyclist and winding stairs in a critique forum in Flickr and people started bashing the photograph like it was captured by a n00b who can’t even take a sharp image.

I have to be honest and I am not afraid to tell you that I have been there. How do you think I ended up with a Nikon D700?! I thought that my photographs will become so much better if I upgraded my Canon 40D to a Nikon D700 that was three times more expensive. To my disappointment, the D700 produced exactly the same photographs. My photos still looked like they were captured by me. Actually, I have grown a hatred for my D700 because it sucks big time in landscape photography. I’m not talking about IQ. This darn camera gets in the way of how I work (please refer to my comparison of the D700 and K5).

Been there, to some degree, and done that. Image quality has very little to do with capturing a jaw-dropping photograph.Take it from me, your camera is not to blame if your photos are crap. I own two cameras that others dream of having. My D700 and K5 still have not saved me from taking crap photographs.

Nikon D700 vs Pentax K5

That’s not a typo. I’m not referring to Nikon’s crop sensor camera the D7000 but it’s professional full frame D700. Yes, I’m comparing a very good, very capable camera from Nikon vs Pentax’s crop sensor K5.

First things first. Both cameras are very good. If you decide to buy either of them, you can be assured of professional image quality output. If your photos are still junk then there’s no one else to blame but yourself.

I bought the D700 because it was on sale at an outrageous 40% off brand new from a legit (not grey) shop. Who could possibly resist that?! And besides, I have already invested in Nikon film cameras so it makes perfect sense to get a digital full frame that can share my existing lenses. Shifting from Canon to Nikon was a necessary evil I had to do but it wasn’t that bad since I haven’t invested in Canon lenses. All I had was the 17-85mm kit lens glued to my 40D. To be honest, I miss that camera. It was very capable, easy to use and infinitely customizable. Which brings us to my major gripes about this Nikon D700:

No memory for custom settings!!! What other modern DSLR camera can’t store your favorite settings aside from Nikon? You expect a camera as expensive as the D700 to be capable of storing user settings in dedicated memory banks. I shoot mostly landscape but I carry only very basic equipment: one camera, one lens and tripod. I never used filters (until recently) except for the default UV to protect my lens from salt spray and dust. If the scene is too contrasty, I bracket and use HDR technique. If you shoot at the proper lighting conditions, you don’t need filters because you could always do that in post. Which means, I expect my camera to do (reasonably) everything I ask it to do. Like bracketing 3 different exposures at 4EV wide, shooting at high speed using the built in timer to avoid camera shake. Unfortunately, the D700 can’t do that!!! To bracket at 4EV wide you need to shoot 5 frames, not 3. If you want high speed shooting, you can’t use the timer. How stupid is that?! And careful if you enabled bracketing mode because to shoot normally you will have to wrestle the darn camera like this: press that small button near the lens mount, turn the thumb wheel twice to cancel the bracket. If you want to bracket again, repeat the same procedure. Now if you are dead serious with HDR, you want at least 8EV wide brackets. That means 9 frames on the D700. As if Nikon RAW files are small. As if your shutter lives forever. Did you just shoot that cat at ISO 1600 in broad daylight? Ooops!!! It would be nice if you could easily reset your camera to your favorite settings to avoid the bloopers, yeah? And please don’t mind the exposure scale because going left is positive and going right is negative (yes, Nikon failed high school algebra). But there is a setting to invert that hidden somewhere deep in the stupid menu. You can read the very thick manual if you are unsure. But careful because that only changes the exposure scale. Everything else will still be in reverse. Seriously, WTF?!

Here comes Pentax K5. Fully weathersealed, built like a tank, in-body stabilization (which means all lenses including manual focus from the 80’s are image stabilized), lighter and way cheaper. And dig this: FIVE, as in five, custom settings memory banks!!! You can couple bracketing with timer. You can bracket 8EV wide with just 5 frames. There’s more: automatic mirror lockup in timer mode! How cool is that! The camera does not get in the way of shooting. It does what I want it to do. It’s the landscape photographer’s dream camera! Enough said. Anything I add here would only make the D700 look like it was crafted by amateurs.

Having said those harsh words against the D700, it still has a special spot in my photography. In controlled environments (e.g. portraiture) it’s still my camera of choice. And the fact that I have invested in quite a few Nikon mount lenses, it makes sense to keep it until it dies.

And that’s why my D700 is gathering dust while my K5 goes wherever I go.