FF vs APS-C lenses

[gr2k]

i'm curious about one thing..so far all the reviews/specs i've read, in general APS-C lenses have higher resolution (MTF) than FF lenses (not considering the high-end FF lenses)

question is: does it matter in field performance?

personally i'm on an FF lens now and i can't tell the diff with my past APS-C lenses

didn't know whether to post it under the 'Nikon' or '3rd party' section coz i'm referring to both actually...

[tools4fools]

Not an expert on such teck questions but:
- It might matter if the FF has the same pixel density as APS-C sensor. However D3 has lower pixel density, so no need for higher res lenses (a 24MP D3x would have same pixel desity and maybe it would make difference there?)

- All my old lenses perform well on my D3 except 18-35mm f3,4-4,0. This one is noticably soft in the corners and I would like to replace it with a 17-35mm or even better 14-24mm.

A joy are the primes, 20mm, 35mm, 85mm all perform very well on D3.
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[raclette]

Not an expert on such teck questions but:
- It might matter if the FF has the same pixel density as APS-C sensor. However D3 has lower pixel density, so no need for higher res lenses (a 24MP D3x would have same pixel desity and maybe it would make difference there?)

- All my old lenses perform well on my D3 except 18-35mm f3,4-4,0. This one is noticably soft in the corners and I would like to replace it with a 17-35mm or even better 14-24mm.

A joy are the primes, 20mm, 35mm, 85mm all perform very well on D3.
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for the 20mm (2.8 right?), is it the ais or afd?

[tools4fools]

It's the AF-D.
Haven't used that one too much yet but looked fine so far.
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Just snapped a test shot with the 20mm and the far extreme corners are soft. But it is really the last tiny, tiny bit of the corner...
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[ShaolinTiger]

i'm curious about one thing..so far all the reviews/specs i've read, in general APS-C lenses have higher resolution (MTF) than FF lenses (not considering the high-end FF lenses)

question is: does it matter in field performance?

personally i'm on an FF lens now and i can't tell the diff with my past APS-C lenses

didn't know whether to post it under the 'Nikon' or '3rd party' section coz i'm referring to both actually...

Well it's to do with physics really, APS-C lenses are basically slightly smaller FF lenses, they have more than APS-C coverage but not quite FF.

They do this due to physics, the sharpest part of the lens is the center, so basically these 'DX' lenses are just using the sharpest part of the glass to focus give full coverage to a APS-C sensor.

Now a FF lens is a different beast (that's why they are bigger, heavier and have less zoom range), they are generally softer corner to corner than DX lenses due to the above, FF sensor will really test a lens if it's sharp corner to corner because it's using ALL of the glass, even the not so good parts.

That's why FF cameras place a lot more demand on the lenses and poor lenses will show much faster on FF cameras than crop cams.

In reality the APS-C lens will be sharper across the frame, probably at f/8-11 they will both be about the same (comparing high quality DX and FX lenses).

[gr2k]

ahh icc thx for all the info :)

[tools4fools]

ST, a question:

What you write is correct for a FF lens used on APS-C (DX) camera; only center is used, corners not.

But then DX lenses have a smaller diameter designed for DX cameras and do use their corners too, no?

http://www.cameralabs.com/reviews/Nikkor_kit_lens_group_test/page4c.shtml
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[ShaolinTiger]

ST, a question:

What you write is correct for a FF lens used on APS-C (DX) camera; only center is used, corners not.

But then DX lenses have a smaller diameter designed for DX cameras and do use their corners too, no?

http://www.cameralabs.com/reviews/Nikkor_kit_lens_group_test/page4c.shtml
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To a degree but not as much as a FF lens.

Put it this way, you CAN put DX lenses on FF camera and have vignetting, the amount of vignetting may give you an indication of how much of the lens is actually being used.

The center performance is best, as you move away it gets worse, as for the 'corner' I don't think it's the very edge of the lens in the case of DX lenses as it is with FX lenses.

[gr2k]

i think just a rough estimate:

FF lens = provides full image circle
DX lens = provides 5/6 image circle
DX sensor = uses 3/4 image circle

[kyreoo]

Accordingly the FF (FX in Nikon term) lenses giving you much controled in term of vignetting if you mount it in DX camera. This is the result of centre croping in the frame which exclude the outer side of the image. Mean that, you have a less vignetting... Furthermore the FF lense is better of distortion controlled... Happy buying

[gr2k]

yes i'm aware off the reduced vignetting + distortion..but what i'm asking is the image resolution

[tools4fools]

Dunno, but the image resolution would be depending on your camera, no?

However lens needs to be of higher resolution to be able to make best out of all those pixels on sensor as pixel densitiy is higher.

12MP on FF camera can use lower res lens as pixel density on sensor is relatively low (and lens diameter is bigger).
12MP on DX camera has higher pixel density on sensor and needs higher ers lens to resolve same quality as FF.

Kind of similar as with medium format lenses: they are lower resolution than 35mm lenses yet image quality of medium format is better. Simply because of larger size.

The lens has to be adjusted to the sensor behind it in all system. The more pixel you pack on a small sensor the highe res the lens in front should be.

Haven't seen any direct comparisons of lenses in regards of resolution however so at the end of day can't say if DX really are higher res.

Another thing to take in count would be diffraction - diffraction itself limits the res at a certain point and even a high res lens wouldn't be of much use if you step it down a bit and diffraction kicks in.
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[gr2k]

not the 'megapixel' resolution...as in Modulation Transfer Function (MTF) resolution...or rather how much 'optical information' passes through the lens..

though i'm beginning to get the feeling it's not so much of the FF/APS-C but the lens design instead which coincidentally, the newer (supposedly better) DX lenses would have a better architecture as compared to the older FFs

*anyway thx for the explanation bro :)

[tools4fools]

I know what you mean...

For higher megapixel density you need more lens resolution (optical info passing).

Actually remembered that the Germans take their testing serious and they do have MTF resolution for many lenses in the reviews.
After checking quite a few it seems:

- New (expensive) FF and DX lenses are best. Like 14-24mm or new 24-70mm. Guess you get what you pay for...

- Lot of older fast lenses - be it primes or zooms - don't perform so great fully open (nothing new here) but are still en par with DX lenses if stepped down to f4 or f5,6. Maybe slightly lower at the most.

- Cheaper zooms - both DX and FF - seems to have a sweet range where they perform well - and don't perform very well on other end/ranges....

- DX zooms seem to suffer from softer corners the same way as FF lenses...

Looks like bottom line is:

- new (epensive) lenses perform better than old ones, never mind if DX or FX. Some of the best perfomers are FF, 14-24mm and 24-70mm.
- Certain DX lenses perform a bit better than old FF lens. However only certain...others don't...
- Cheap, long zooms usually are quite weak at one end...

Compared to lenses I own these tests seem all right: my 18-35mm 3,5/4,5 is the only lens that doesn't convince me on my D3 and it does not fair very well in their tests either...

Photozone tests, btw:
http://www.photozone.de/Reviews/Nikkor%20/%20Nikon%20Lens%20Tests
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[gr2k]

ahh i guess that's answered then..thx for all the info :)