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I've always used cropped-sensor cameras, now I'm in the process of deciding for a full-frame camera. While I've read about the differences between them, I'm still getting my mind around this, and it just came to my mind a question for which I haven't been able to find an answer on the web.

In a full-size sensor camera, I wonder if its possible to set it in the way to obtain an image with the characteristics of a cropped-size one (image size, resolution, pixel area and so on).

The thing is that for my work (architecture), I might need to take pictures using both cameras and compare the luminous situation, if I get the full-size one I'll have to use my previous cropped size to do this comparison. However, I don't know if this comparison would be valid with two different cameras in terms of sensor size.

I found this similar question but still not 100% answering my question: Do full frame sensors gather more light than crop sensors?

I'd appreciate your opinion on this

Ste

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    "[A]n image with the characteristics of a cropped-size [sensor]" makes no sense; sensor size is not a characteristic of the image. – user29608 Oct 30 '17 at 0:08
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Certainly Nikon full frame DSLRs accept DX lenses (lenses for cropped bodies) and will create that smaller size image. It has an option for that, and another option to switch automatically when a DX lens is mounted. I assume it is a common feature on several brands, but don't know about others.

In Nikon's case, full frame is called FX and the cropped frame is called DX. Comparing FX when cropped this way to DX size, the DX size is 2/3 the pixels wide and 2/3 the pixels tall, which ends up with 44% of the number of megapixels. If cropped that way, 24 megapixels FX becomes about 10.3 megapixels DX, and of course, the smaller image has to be enlarged 1.5x more (to view the same size).

If both are a 24 megapixel sensor, then of course both create 24 megapixels, but if you instead crop the full frame to DX size, then you will only have 44% of the FX megapixels.

You mentioned comparing luminous and if full frames see more light than cropped frame. That answer is no. Both at f/8 will give exactly the same exposure. The luminosity per unit area is the same if lens is at the same f/stop. Sensor size does not affect that. The larger frame may collect more total light, but it is distributed over a larger area, and so the luminosity per unit area, and therefore the resulting exposure is exactly the same. You will not see "more" light.

The difference you will see is that (with the same lens), the full frame sees a wider field of view (1.5x wider dimension), and the cropped sensor sees a smaller cropped view. The wider view may be beneficial for architecture, but you will of course have to buy FX lenses.

  • Hi again and thank you for your answer. Then, other than using lenses to get the 'cropped' effect, another choice would be using specialised software? If I just edit the 'larger' image obtained with the full-sensor camera, just crop it to fit the size of the the 'cropped sensor' one, then the comparison will be valid in terms of the 'brightness of the scene'. They will basically represent the same luminous situation (luminance, for instance), but in different size images. Is that right? – Pollux Oct 30 '17 at 19:32
  • Sorry, I'm unaware that the "cropped characteristics" and "luminous" situation exist. Is there any specific goal that you seek? The "cropped" sensor is simply smaller, it just takes smaller images, exactly like using smaller film would. Smaller film could be called cropped film with exactly the same meaning, it's just smaller. There are many sizes of cropped sensors. A cell phone has a tiny sensor, less than 1/7 the size of full frame. With their suitable lenses, they can all take the same picture, which differs only in image size and degree of enlargement required to print or view it. – WayneF Oct 30 '17 at 22:37
  • The larger image might print a better quality large picture, but it can also be larger than the need requires. Yes, some full frame DSLR (certainly Nikons) have options to use lenses for cropped sensors to create the same smaller cropped images. Except their difference from a real cropped sensor is that they will only have 44% of their pixels remaining after this crop smaller. Cropping is like using scissors to trim a paper print smaller, less is left. I'd choose the larger image if available. The full frame image also has the wider field of view, because it has not been cropped smaller. – WayneF Oct 30 '17 at 22:37
  • I need to compare two luminous situations (under different lighting, lamps, wall colors and so on), that's why I need two cameras. I was worried that by using different size sensors, one would be more exposed than the other, and for this reason I' wouldn't be able to compare them. But I think that I've got the idea, either using lenses or with some post-editing, the task can be carried out with different sensors. Thank you again for your help. – Pollux Oct 31 '17 at 4:24
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Many full-frame cameras allow you to mount a cropped-sensor lens on it. This will give you the same output and very similar resolution. For example, if you put a DA lens on a Pentax K-1 which is a 36 MP full-frame, you get a 16 MP crop from it which is the same as if you had shot with a K-5 camera.

Nikon offers a similar setup. Both even black-out areas of the full-frame viewfinder so that you can see what you will be capturing, although the framing is less precise. Sometimes a 100% coverage OVF on a full-frame shows 97% coverage on an APS-C camera.

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