Bipod wrote:
This is incorrect. I am not talking about keystoning, I am talking about barrel distortion
and various aberrations (particularly Petzval image space curvature).
14 mm prime is super-wide. So is a 14-24 zoom. All super-wide lenses have large amounts
of distortion-- the ultimate being a fisheye lens. Your are comparing two lens with very
high distortion! Photograph a grid or a piece of masonite pegboard with your super-wide lenses
and you'll see what I mean.
I was talking about the OP's 15 - 85 zooms. All zoom designs are a compromise, but especially
those that go from ultra-wide to normal to long. They all suffer from more aberations and
distortion at at lease some focal settings. This is a well-known fact of optics.
I would except to see little if any distoration in a good 85 mm prime. But I'll bet that zoom set to
85 mm has plenty. All he needs to do to find out is photograph a brick wall or a piece of pegboard.
It is sometimes possible to correct distortion in post processsing, provided it is is simple barrel or pincushion
and there are no other aberrations. But why not just use the correct lens instead?
Aberrations are much more difficult to test and characterize. Most zooms have significant curvature of field.
So when photographing an architectural subject such as a well, it will only be truly sharp in the center of field.
Of course, if all someone shoots is weddings or passport photos, then any old lens will do. Might as well just
leave one zoom on your miniature format camera all the time. You'll never notice distoration or unsharpness.
But people who photograph architecture for a living use view cameras -- to eliminate the keystoning you
mentioned. But they do not -- ever -- put a zoom lens on a view camera.
Zooms have gotten a lot better than they used to be. So have electric bicycles--and it's possible to spends
thousands of dollars one. But that doesn't make it a motorcycle.
If you can't admit your zoom lenses are not apochromats, can you at leaste admit that your electric bicycle
isn't a Harley?
This is incorrect. I am not talking about keyston... (
show quote)
Well, when you get to specifics and meaningful differences, a little fact checking is in order-
Here are two reviews - one of the 15-85 and another of an 85mm F1.8
https://www.opticallimits.com/canon-eos/465-canon_1585_3556is?start=1https://www.opticallimits.com/canon_eos_ff/419-canon_85_18_5d?start=1If you look at them carefully - you'll see that at 85mm, the zoom shows .32% pincushion distortion, and the prime lens .24% barrel. Neither has noticeable distortion at 85mm. So much for your expectation that the zoom lens would have "plenty" of distortion. The amounts are statistically equivalent.
Here are two reviews - 14-24 and the 20mm f1.8 prime
https://www.opticallimits.com/nikon_ff/975-nikkorafs2018ff?start=1https://www.opticallimits.com/nikon_ff/447-nikkor_afs_1424_28_ff?start=1You'll see that the prime lens shows barrel distortion of 1.6%, and the zoom at 21mm shows only .505% barrel - which is barely noticeable.
Distortion is less of an issue today - and even a lens with horrible complex distortion, like the 14mm F2.8 Samyang/Rokinon/Bower - which has about the worst complex distortion I have ever seen in a lens that I have used - can be corrected -
https://www.opticallimits.com/canon_eos_ff/532-samyang14f28eosff?start=1https://www.dpreview.com/forums/post/57172988Oh, and by the way, the 5.29% barrel/complex distortion in this prime lens is considerably higher than the 3.91% in the Nikon zoom. Just sayin'
I began shooting architectural work for my architecture professors in the early 70s - they needed reasonably priced work to add to their company portfolios. Later I did a bit more work for hire, and had a nice business doing work for large contractors, developers and interior designers. My camera of choice was a Sinar P 4x5 (and later a P2), and an assortment of Nikon and Rodenstock lenses to get it done. I used the large format camera for the ability to control perspective, which includes vertical and horizontal keystoning, and with the swings and tilts I had better control over
depth of field. For what it's worth, the reason you don't see zoom lenses on large format cameras is that no company actually makes one.
Field curvature is a fact of life, l lenses have field curvature, btw. But it is not an insurmountable one, if you understand your gear and use it correctly. And each lens can have a variety of curvature effects, depending on subject to camera distance, aperture and focal length (if using a zoom). Your claim that if you shoot a wall with a lens that has field curvature , it will only be sharp in the center is pure ignorance. All lenses have field curvature. Clearly if you know your gear and focus carefully, you can decide to strike a happy medium when you have a lens soft corners - you re-focus to a point in between the optimum focus for the center and that for the edges - and stop down sufficiently to allow depth of field to provide a reasonably sharp image that has good sharpness across the entire field. When using a view camera it was standard practice to load a 4x5 polaroid back to check image sharpness and adjust accordingly. If you actually shot large format you'd know that.
Good article illustrating how field curvature works and why it isn't necessarily a bad thing:
https://petapixel.com/2016/12/21/field-curvature-tricky-problem-photography/And how common it really is:
https://photographylife.com/what-is-field-curvatureWhich "true" APO lenses do you own?
So much for your claim that primes are better in the distortion/curvature/aberration department than zooms. Such is not always the case, and using generalities to make a case reveals that you do a lot of keyboard surfing and have considerable googling skills, but have little practical experience.
BTW, on another note - please use a decent spell checker -
distortion not distoration
processing, not processsing
wall, not well
aberration, not aberation
least, not leaste
And on a final note, I suppose you've never heard of the the Harley LIVEWIRE™ - which is - you guessed it - an electric Harley that costs $29K.
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