@aki_hartikainen Yeah there is more light overall because you have a larger image in terms of larger FOV, so obviously there's more light captured, your capturing a larger scene. It doesn't change the exposure of any given part of that image, as is reflect by your demo photos.

@sangye The FF sensor will give an illusion of more (or less) DOF though, as there is more room out of focus and less in focus, relative to the view. I should have mentioned that, I suppose, but it's unimportant because I'm sure someone would argue that the DOF does indeed change. This is the same as what you pointed out in the demo photos, that there is more white wall to see. DOF is just easier to judge by eye than exposure.

@tmcat but I suppose you do not deny that putting a lens in front of the house window to focus more light or growing the window size has any different effect on the exposure inside the house? Atleast I hope nobody seriously wants to refute that ;-)

Okay, but the histogram showed the exposure inside the house. Not outside. There was increase inside the house. Exposure outside the house did not change, however.

I see it, but if it could be agreed that changing the window size changes exposure on the inside of the house (or camera), then we are starting to see the big picture and not just one part of it. Quite literally too.

aki: you are talking about optical alteration, which normally scatters or concentrate light. A sensor crop has no optical alteration. It´s is just a smaller image given that everything else is the same.

Ask yourself this: do you think that your nikon lens image circle becomes smaller or weaker in strength just because you happen to use the centre part of it, rather than the whole image circle?

You are mixing up things which has nothing to do with the matter.

Have you ever used a light meter? Does it have options for different sensor sizes? No? Well then, there you are. They had different "sensor" sizes back in the days of film. You can easily test shooting with full frame and half frame (with the same lens, same film) if you still are intent on discussing this further. No engineers there to alter sensor / film sensitivity.

Edit: your window analogy does not work in the case of sensor sizes (as you made it out). The window is the lens. Change it however you want. Inside, on the back wall where light is reflected, it doesn´t matter if you choose a 10 cm square, a 1meter square or however big a square that can be got from the window reflection - they will all be just as bright.

I did not say it was better. I simply pointed out something that exists, even if it is transparent to the end user for the most part. But becomes visible in certain circumstances, like building a focal reducer to get increased image brightness.

I do consider getting a camera with bigger sensor but I have no need to promote such thing for whatever reason. The point is that we are not just picture snappers here, but should be able to "up our game". Not everything is always incredibly simple or obvious, but does it have to be?

Somebody clearly was on the right track at the beginning of this topic, and that got my attention. I have had this same debate a few times on different forums and I am slightly worried seeing that such large principles like crop and magnification and their effects are ignored so willingly. What else is being ignored or perhaps even denied existence ;-)

@RRRR "A sensor crop has no optical alteration. It´s is just a smaller image given that everything else is the same."

No disagreement there. But the cropped image is smaller and needs to be magnified more for viewing. Magnification has a penalty in either brightness or image quality all else being equal. The loss of brightness has to be compensated somehow and there are a myriad of ways to do it either optically or electronically. But it still has to be done.

Brightness remains equal in front of different cameras, thus same exposure for different image sizes.

@akin_hartikainen

It's not the same thing at all. The lens is what gathers the light and directs it to the sensor. The focal reducer directs more light into a smaller area, thus increasing its intensity. A sensor doesn't work this way. The same amount of light travels through a lens with a given r stop no matter how large the sensor of the camera it's attached to.

"But the cropped image is smaller and needs to be magnified more for viewing. "

It does not NEED to be anything. A cropped image is smaller. Period. If you choose to use your optical magnifying glass or digital re-sizing that is up to you, but the only thing you loose by enlarging the image digitally (which might be something you want to do in post; is resolution. - or to be more precise; you do not gain any resolution by re-sizing)

@aki_hartikainen must I remind you, this topic started because nobody agreed with you and every one who did learned not to. Maybe you don't really understand what crop sensors do in relation to focal length, exposure & f stop. The info is out there, though, for you to find. This topic is a flame, so it should be used as such, instructions can be found elsewhere.

Of course a larger sensor collects more light! There is no question of that, however, per square inch / cm / mm or whatever the average light acquisition is the same, if the sensor property is the same. It should not be so hard to grasp?

@tmcat "The info is out there, though, for you to find."

I have seen some of the info and it is not much different from what I would get from this thread. For the most part the enlarging and magnification that is required to match different original sizes is ignored.

This is a symptom of less capability to understand even simple concepts and principles. Anybody with some first hand experience with dark room and enlargers could relate immediately. But that was 30 years ago. Today it is different, much to my dismay.

@tmcat "It isn't hard to grasp at all, @aki_hartikainen even constantly brings up these examples himself... For example"

A 10 watt image is not going to be as bright as 40 watt image. But if you use 40 watts to display a 10 watt image, then they will have the same brightness.

Not difficult in the least.