Hi,
The lens was focused at 3 meters, thanks.
Hi,Field curvature is just one of the major aberrations, and a major part of lens design is about trading off the different aberrations against each other and against other considerations (size, price, and so on). So for example, there' s no particular type of glass that minimizes field curvature. In that Nikkor, there might have been some glass that used in one element enabled a tradeoff that reduced field curvature, but it doesn't mean that plunking that glass into some other lens or some other element would have a good effect.
Juan, in your example of a 35mm lens on 35mm film, at f/8 and focused at 2 meters, the conventional depth of field (with a circle of confusion of 0.03mm) is roughly from 1.4 to 3.2 meters. Probably not enough to bring the house into sharp focus even with a perfectly flat field lens. Try for example the DOF calculator at https://www.dofmaster.com/dofjs.html In contrast, focusing at 3 meters, the DOF is from 1.9 to 7.2 meters. While curvature of field may have affected your photographs, the other issue is that one loses DOF very rapidly as one focuses closer.
You don’t want to see graphs yet you want to understand the aberration? I’m sorry, to truly understand what’s going on requires study of the underlying math and physics. It’s not something that can be put readily into layman’s terms to advance your understanding beyond myths, half-truths, and marketing BS. There’s just no way.
First thing to understand: Field curvature isn’t a magical cause of all a lens’ woes. Optical fabrication and assembly tolerances are significant contributors to image degradation in a modern lens, and could just as easily be the root cause to your experiences as anything. Any review or test of a lens which draws conclusions about the design based on a single sample should be immediately suspect: The reviewer has no idea where that lens falls in the performance distribution for that design, and for consumer-grade optics such as used for photography the distribution can be quite wide.
underlying that is the effect of balancing of all the aberrations, which for modern optics really must be viewed as Zernicke terms as the higher order aberrations are often balanced against and of similar magnitude as the residual third order aberrations.
if you really want to understand field curvature, and not just myths and legends, I highly recommend accepting the fate that it requires maths and follow the link I provided above. You will not gain a full understanding there, but it will shed light on the tools required to truly understand the phenomenon.
If however you are happy with myths and legends, then yes.. field curvature causes everything.
Do a search.Why do you believe that lens design can tame diffraction? And which lens are you talking about? I ask because I'm not aware of any 35 mm lens, if that's what you meant, that is a double Gauss design. Many 50 - 60 mm lenses for 35 mm cameras are 6/4 double Gauss designs or variants, but 35 mm?
Best anwser to this thread's subject.complete broken biscuits by op
Thank you, grain...In practice, getting an idea of the field curvature of one's lenses is easy. Take a picture of something textured and flat, stretching away from the camera. For close up, a newspaper or similar, for longer distance, flat lawn should work. At higher magnification, the plane or curve of focus will be obvious.
I doubt you will find much about the lenses' behaviour on film. Field curvature is different on digital due to sensor cover glass. Towards the corners of the sensor, light must travel for a longer distance through the cover glass, which has a different refractive index from air. No such effect with film.
I don't know who you're talking too... I don't think field curvature causes anything.
And no one here has said field curvature causes everything: you need help, seriously...
And about the math and graphs ways of understanding what happens on photographs, that was not needed at all by Nadar or Atget or Cartier-Bresson or Frank or Winogrand.
I have no interest at all in what you feel is important, I'm sorry.
I live inside a different field called Photography.
And we all (photographers) understand field curvature very well.
Lens designers study those fields differently.
Enjoy your math and graphs, and also enjoy photography whenever you feel like doing it.
Oh yes, I have had that situation. A Jupiter-12 has crazy field curvature.Thank you, grain...
You're right.
I thought maybe some other forum members could have found situations where field curvature required, as in the case I explaned, an unusual f-stop.
Have a nice day.
In case you weren't aware, Nodda Dumma designs lenses for part (most?) of his living.I don't know who you're talking too... I don't think field curvature causes anything.
And no one here has said field curvature causes everything: you need help, seriously...
And about the math and graphs ways of understanding what happens on photographs, that was not needed at all by Nadar or Atget or Cartier-Bresson or Frank or Winogrand.
I have no interest at all in what you feel is important, I'm sorry.
I live inside a different field called Photography.
And we all (photographers) understand field curvature very well.
Lens designers study those fields differently.
Enjoy your math and graphs, and also enjoy photography whenever you feel like doing it.
Do a search.
Yes, Cicala's/lensrentals MTF graphs have been around for some years, but despite their multiple and possibly accurate graphs, I never found real photographs showing real life differences between the most used rangefinder 35s by Leitz/Leica/Zeiss/Canon/Nikon/Voigtlander in a comparative or comprehensive way. Thank you.
Why do you believe that? Its true that they don't all measure MTF at the same spatial frequencies or apertures but that doesn't mean one can't base decisions on them.If a company provides MTF curves, each uses its own standard so the cannot be compared.
Do a search.I'm interested in learning about field curvature as we find it in 35mm lenses for 35mm rangefinders... Articles, links, books, and of course general comments from forum members...
I just thought there was an optics/lens design forum, but maybe I'm confused and it was not here at Photrio...
Thanks.
Why do you believe that? Its true that they don't all measure MTF at the same spatial frequencies or apertures but that doesn't mean one can't base decisions on them.
Oren, not to quarrel with you, but I'd love to have a reference for published MTFs with diffraction.
The readings at 10 lines per millimeter measure the lens’s contrast ability ( red lines), repeating fine parallel lines spaced at 30 lines per millimeter measure the lens’s sharpness ability (green lines), when the aperture is wide open.
Dan, I agree with you that the Sigma data raise as many questions as they answer. But I think that underscores the point that published MTF data for small-format lenses are a swamp; use for comparison purposes at your peril.
Tangentially and FWIW, the 70mm Sigma Art macro is superb, at least for my current use of it on a Sony A7RIV for high-resolution film copy work.
In practice, getting an idea of the field curvature of one's lenses is easy. Take a picture of something textured and flat, stretching away from the camera. For close up, a newspaper or similar, for longer distance, flat lawn should work. At higher magnification, the plane or curve of focus will be obvious.
I doubt you will find much about the lenses' behaviour on film. Field curvature is different on digital due to sensor cover glass. Towards the corners of the sensor, light must travel for a longer distance through the cover glass, which has a different refractive index from air. No such effect with film.
Do a search.
For all but the really dumb questions, this is the most asshat answer ever. This is a discussion forum right??? right???????
If everyone 'just did a search', this forum would not exist.
I think the OP question was valid and asking for advice and possibly reference material to learn about a technical subject.
Contrary to popular belief, web searches can return pretty superficial or incoherent responses to questions that have common words or phrases.
I think the OP question was valid and asking for advice and possibly reference material to learn about a technical subject.
I think as Mike said you might have missed the context of that particular post. I try to be helpful around these parts and perhaps you'll see that if you review my posting history.For all but the really dumb questions, this is the most asshat answer ever. This is a discussion forum right??? right???????
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