Exposure vs. Exposure

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Exposure vs. Exposure
10 months ago

In the last two or three days it became clear to me that there is a group of people who seems to be very upset about the fact that in most image editors or RAW converters there is a tool called exposure which is usually meant to digitally simulate the actual exposure.

The reason why these people don't like it is because it's not in line with their bible that comes in the form of a Wikipedia article in which it states that: "In photography, exposure is the amount of light allowed to fall on each area unit of a photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region."

Personally I don't have any problems with this definition but the interesting part is how this group of people use this definition to actually defend their fallacies.

For example: if you show them these two pictures...

...and based on them claim that in order to make the first picture as bright as the second one you'd have to increase ISO to 3200 obviously (as it was done in the second picture) or change exposure settings (as the widely used idea of exposure triangle would suggest) and there is where you will get in trouble with them and sooner or later you will be presented this image:

as you can see the brightness of this last image is fairly similar to the second image even if the exif settings actually tell you that it should be as dark as the first image also because this image IS actually the first image which I simply brightened using the exposure tool in photoshop. of course I could brighten it using other tools as well such as brightness, levels, curves etc. and get similar results but that's not really important here.

what this group of people would at this point claim is that no exposure was not altered here but brightness was. they base this claim also on the fact that the exif files of both the first and third images say that they were both taken with f/6.3 and 1/800s. but pay attention... they were both TAKEN... now, can we actually claim that the third image is actually the image the camera took? well, in some sense yes but actually no. what the camera took is reflected in the first image. what is reflected in the second image though is the change I digitally made to what the camera took. that basically means that the exif data of the third file is not really reflecting what is going on the third image but it's reflecting what is going on on the first image and as you can see what is going on on the first image is pretty much a very different story than what is going on on the third image. one thing to note here is that what I did by editing the first photo was to digitally simulate the exposure settings of the  second photo.

so, what will this group people do at this point since I dared to suggest that what I changed in the third image was exposure? well, they will bring out their bible and read the definition of exposure to you. and of course you can only agree with them that of course what you changed was not the amount of light allowed to etc... but you could still work things out saying that exposure change was digitally simulated and that's exactly what happens and that's exactly what the exposure tool is meant to do.

now, this group people would rather call this changing the brightness but isn't that exactly what we control with exposure, so with the amount of light allowed to etc.? indeed it is. with exposure we control the brightness of the image. more light we allow to reach the sensor more bright the image will be. now you can see why adobe and many others call their tool exposure or at least why it makes sense to do so? it's because it controls the brightness of the image in a similar way that the actual exposure does. does anyone from this group of people have a problem with the fact that photoshop have tools that are called dodge and burn? does this group of people even know what dodging and burning actually mean? lets asks the "bible": "In a darkroom print from a film negative, dodging decreases the exposure for areas of the print that the photographer wishes to be lighter, while burning increases the exposure to areas of the print that should be darker." and is that what is going on in photoshop? nope, photoshop is only digitally simulating dodging and burning so why would anyone have a problem with photoshop calling one of their tools exposure?

so, what's my point? my point is that it is not only ok for us to accept the idea of exposure being changed inside photoshop (of course keeping in mind that it's just a digital simulation of the actual exposure) but also necessary in order to prevent such fallacies as the picture examples exposed where this group people were claiming exposure didn't change simply because the exif numbers remained the same and no actual exposure took place. and yes, the actual exposure not only didn't change but it even became irrelevant after digital exposure (or brightness if you so wish) was applied so referring to it after changes affecting brightness have been made is completely irrelevant and wrong.

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