APS-C less sharp than FF?

[tayassu]

I've been wondering about this for long time:
When I go to TDP and compare a FF and a crop body with the exact same lens settings, the crop sensor is waaay less sharp. Why is that? Doesn't seem logical to me...

 

[Sporgon]

I presume it's because they are twice the magnification. I think the TDP APS crops are very misleading. If TDP did MF crops using the same method they would make FF look bad in comparison.

But then I suppose they do remind us that APS has to be enlarged more from the original size of image captured on the sensor, and tends to need more sharpening than FF.

 

[tayassu]

Ok, thanks.
I ask this because I might get the chance to get my hands on a 5DIII for a very low price and I was wondering about the supertele option. According to TDP, it looked like Sigmas 150-600 S on a FF is as good if not a slight bit better than the 100-400 II on crop, although it is common knowledge the Canon lens is way sharper than the Sigma. With only that knowledge there'd be no sense in keeping my 7D, but now it looks like it will stay either way.

 

[mistaspeedy]

The pixel density of APS-C sensors is a lot higher than full frame cameras. Therefore, you will start to get limited by the lens quality a lot before a full frame sensor would.
Remove the lens limitations (use top quality lenses) and then APS-C sensors can really shine.
Looking through various dxomark lens scores with different camera bodies seems to support this as well.

 

[Sporgon]

Ok, thanks.
I ask this because I might get the chance to get my hands on a 5DIII for a very low price and I was wondering about the supertele option. According to TDP, it looked like Sigmas 150-600 S on a FF is as good if not a slight bit better than the 100-400 II on crop, although it is common knowledge the Canon lens is way sharper than the Sigma. With only that knowledge there'd be no sense in keeping my 7D, but now it looks like it will stay either way.

The smaller the format, the better the lens you need. In practice a moderate lens (in terms of resolution) on FF will give the same performance as a excellent lens on APS.

The pixel density of APS-C sensors is a lot higher than full frame cameras. Therefore, you will start to get limited by the lens quality a lot before a full frame sensor would.
Remove the lens limitations (use top quality lenses) and then APS-C sensors can really shine.
Looking through various dxomark lens scores with different camera bodies seems to support this as well.

That's true in practice, but on the TDP crops even the Sigma 18-35 f/1.8 doesn't hold up well against moderate lenses on FF, which is why I say from a practical point of view I think they are misleading.

 

[mistaspeedy]

Yeah... only the very best of the best lenses will do... something like the Sigma ART prime lenses.

Realistically speaking, you are better off getting a full frame camera and decent glass, than trying to squeeze every last bit of quality out of a APS-C sensor with very expensive prime lenses.

 

[Sporgon]

Yeah... only the very best of the best lenses will do... something like the Sigma ART prime lenses.

Realistically speaking, you are better off getting a full frame camera and decent glass, than trying to squeeze every last bit of quality out of a APS-C sensor with very expensive prime lenses.

For resolving far away detail that's small, such as landscape photography, I think that is very true. For shooting things that are closer and fill the frame ? I really not convinced that in good light at low ISO you can see any practical difference.

 

[NancyP]

Given the same pixel density for the image, the images should be comparably sharp at low ISO. Bigger pixels get you less noise and better color fidelity at higher ISO. The big question is, do you need portability and handholdability more than low light performance? I haven't personally worked with the new 7D2 files, so I don't know how they compare with similar resolution 6D files.

 

[Luds34]

Yeah... only the very best of the best lenses will do... something like the Sigma ART prime lenses.

Realistically speaking, you are better off getting a full frame camera and decent glass, than trying to squeeze every last bit of quality out of a APS-C sensor with very expensive prime lenses.

For resolving far away detail that's small, such as landscape photography, I think that is very true. For shooting things that are closer and fill the frame ? I really not convinced that in good light at low ISO you can see any practical difference.

+1

I agree, could not have said it better. No real practical difference in good light (low ISO).

 

[wsmith96]

For the TDP test, the smaller pixels of the APS-C camera's always look a bit fuzzier compared to the FF cameras. APS-C senors demand good glass, such as the 200 F2 or 300 F2.8 prime lenses to match the apparent sharpness of a FF camera in this test. That doesn't mean that your pictures will look bad though. Take for example the 17-55 f2.8 lens. It's fuzzy on the TDP comparison page, but when used in the field, it performs great. FF will always be a bit sharper, but unless you are printing really big, you most likely won't be able to tell the difference in sharpness. Now, depth of field is a different story.

 

[JohnDizzo15]

If we are just talking purely about sharpness, there are a few things to take into consideration. It is not as simple as one being sharper than the other anymore.

I can tell you right now that between the various systems I have shot in the last two years (a7r/551.8, 6D/5D3 with various high quality lenses, EOS M with 22/2, Fuji xt1/23 & 56mm, and pentax k5IIs with 50/1.8), the sharpest (and most consistently sharp) results I have gotten have been from the Fuji and Pentax rigs. Oddly enough, both of those happen to be APSC.

You have to consider the AA filter (strong, weak, not present), pixel density and how it affects your shutter speed requirements, glass, etc.

If we are talking other things like varying resolutions (ability to zoom in), DOF, etc, we are no longer talking solely about pure sharpness at average/normal viewing mediums.

Again, what I have referred to are the results I have experienced for myself so YMMV. But I know that I am not the only one who has used all or some of these systems and come to the same conclusion.