If you are here to understand (why) equivalence (is wrong) then read this: https://dtmateojr.wordpress.com/2014/09/28/debunking-equivalence/
This article is a continuation of my previous post that stirred multiple different forums. I suggest that you read it first before going through this article. Here’s the controversial post: https://dtmateojr.wordpress.com/2014/03/08/debunking-the-myth-of-full-frame-superiority/
Anyway, in an unrelated forum post, a dpreview article was quoted about the benefits of a certain Sigma lens. The quote went like this:
“Sigma’s choice of F1.8 as maximum aperture isn’t a coincidence; it means that the lens will offer the same control over depth of field as an F2.8 zoom does on full frame. What’s more, it will also offer effectively the same light-gathering capability as an F2.8 lens on full frame. By this we mean that it will be able to project an image that’s just over twice as bright onto a sensor that’s slightly less than half the area, meaning the same total amount of light is used to capture the image. This is important as it’s a major determinant of image quality. Essentially it means that APS-C shooters will be able to use lower ISOs when shooting wide open in low light and get similar levels of image noise, substantially negating one of the key advantages of switching to full frame.”
Dpreview may be experts in reviewing photographic gear but it looks like they know nothing about photography itself. That article is completely WRONG. A f-stop is a f-stop. Period. Full stop! A f/2.8 lens will always let through lesser light compared to f/1.8 REGARDLESS of format, be it full frame or APS-C or m43.
I found another very very simple proof: FILM!!!
Yes, you read that right. FILM.
Back when the word “photographer” actually meant something, people shot on film. What’s interesting to note is that a particular film emulsion is often made available for different formats. The famous Kodak Ektar 100 for example is available in either (the measly) 35mm “full frame”, in the much larger 120 medium format and even in ginormous 8×10 sheets! The sizes may be different but the emulsion remained constant.
Those who are interested can check out the data sheet for Ektar here: http://www.kodak.com/global/en/professional/support/techPubs/e4046/e4046.pdf
Here’s the datasheet for Fuji Velvia: http://www.visionimagelab.com.au/_literature_85837/FUJICHROME_Velvia_100F_Professional_%5BRVP100F%5D
Same emulsion, same response, same everything except size!
If indeed, a larger sensor has more light gathering capability compared to smaller sensors then the same film in different film sizes would need to have different emulsions right? If the myth is true then larger films will have to be less sensitive or they will overexpose. Those shooting with 8×10 view cameras will be overexposing their shots if they follow the same data sheet for 35mm film! We know that’s not true. The same sunny f/16 rule applies to 35mm, 120 or 8×10. The same emulsion behaves exactly the same whether it’s 35mm or 120 or 8×10.
There are some panoramic cameras that allow you to shoot in square format as well just by inserting a mask that blocks the sides of the film. You get to use the same film and lens. Now the shooting instructions don’t change. You still expose the film as if you were shooting a panoramic format. If equivalence was even remotely valid then you would have to change your f-stop and/or shutter speed but you don’t. Same lens, same film, same f-stop and shutter speed even if the film size has changed. Film size does not matter!
Plain and simple! Myth has been truly busted the second time!