Can images with FF cameras be sharper and if so why?

[Markus Jais]

Hello,

I like this new science category!

I read quite a bit that images taken with a FF camera like the 5D III, 1DX or D4 are supposed to be sharper than images from a crop camera like the D300s from Nikon or the EOS 7D.
Some websites claim this but don't offer images, other don't offer 100% crops, others say it is minimal and can be ignored, others say it is all nonsense.

What is the truth and if FF sensors are indeed capable of producing sharper images, why is that and is it noticeable in read life?

Markus

[Roger Clark]

Hello,

I like this new science category!

I read quite a bit that images taken with a FF camera like the 5D III, 1DX or D4 are supposed to be sharper than images from a crop camera like the D300s from Nikon or the EOS 7D.
Some websites claim this but don't offer images, other don't offer 100% crops, others say it is minimal and can be ignored, others say it is all nonsense.

What is the truth and if FF sensors are indeed capable of producing sharper images, why is that and is it noticeable in read life?

Markus

Hi Markus,

There are a lot of ifs in the answer.

Case 1, The subject is small in the frame, focal length limited: FF or not is irrelevant and the camera with the smaller pixels will give the most detail on subject. Attached image is an example (7D, 1DIV, 1D3 comparison, 100% pixel crops). I like the 7D image best as it provides the most detail.

Case 2: Given 2 sensors, A and B, each with the same megapixel count, camera A is FF and B is 1.6x crop factor, and one compares the same field of view. IF the sensors have the same quality (same fixed pattern noise, same quantum efficiency), and lenses of equal quality are used, then camera A will produce better images, but because the lens is a longer focal length lens with a larger aperture (for the same f/ratio). The main factor here is the larger lens which delivers the light. The larger sensor enables collection of the more light. It is like my bucket examples I talked about in other threads. A larger bucket enables one to hold more water, but you need a faucet to fill the bucket and it is how much the faucet is turned on which fills the bucket. Same with cameras, it is the lens that delivers the light.

Another factor in case 2 above is the larger lens with the larger pixels are larger relative to diffraction effects, so at a given f/ratio, the larger camera with the larger lens, to give the same field of view, will produce images with better contrast in the fine details. But the depth of field will be smaller. Equalizing the depth of field, requires the aperture diameters to be the same, so then the light levels are the same and the diffraction is the same, so the two cameras produce the same quality image (ignoring other aberrations).

But in reality, sensors in different cameras have different designs, showing different problems in images. For example, I do a lot of night landscape photography. I find the fixed pattern noise in the 5D2 very objectionable (and the 5D3 seems to be the same from reports on the web). So I'm using my 1DIV for more things that I used to use the 5D2 for. And, the crop sensor uses the better area of the lens, cropping the edges. But you have to magnify more for the same enlargement. But some lenses, particularly wide angle lenses really fall apart in the corners, and the crop sensor produces a better image in those cases.

Roger

[Markus Jais]

Thanks Roger! Very helpful.

Markus

[John Chardine]

Hi Markus and Roger- I remember back in late 2008 I picked up a lightly used Canon 5D- FF 12mp. At the time I had a 40D (1.6 crop, 10mp) and a 50D (1.6 crop 15mp) as well. In all circumstances (lenses, f-stops etc), the 5D produced images that were sharper, less noisy and with more dynamic range, out of the camera, than either the 40D or 50D. The effect was very obvious. Perhaps wrongly I don't know, but I put this partly down to a unaggressive anti-aliansing filter in the 5D (?). I posted a comparison of the 5D and 50D in relation to preparing BPN images here:

http://www.birdphotographers.net/forums/showthread.php/27083

Correct me if I'm wrong Roger but I think your Case 2 explains why many think the 7D makes inferior quality images of a focal-length limited subject. With the pixel density of the 7D you can get away with smaller focal length lenses with smaller apertures, so the comparisons are usually biased against the high-mp camera. This the etendue argument.

[Michael Gerald-Yamasaki]

Markus,

Greetings. For all FF vs crop sensor discussions it is hard to disassociate the impact of focal length and lenses. For a crop sensor, it is pretty hard to find a lens that is comparable to the better 24mm lenses on FF for the same field of view (that would be a 16mm lens or there about to get the same fov as the 24 on the FF). On the tele end, it's pretty hard to match the pixel resolution of the crop sensor with a lens for the FF sensor, not to mention that the crop sensor is pulling from the sweet spot of the lens with diminished edge defects (light drop off, etc.).

The lens quality has an impact on sharpness and in the real world one's ability to acquire the higher quality lens can really make the difference in the choice between FF and cropped sensors for sharpness. More so for wide angle (FF has advantage) or tele (crop has advantage).

Hope this helps (meant as an addition to Roger's good points).

Cheers,

-Michael-

[Markus Jais]

Thanks for all your replies. Very interesting and helpful. Markus