Help with my assignment question...
- Thread starter xSitara
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May be something to do with the size of the image circle produced by the 'made for digital lens' being smaller than a 35mm frame size.
jgs001
Brian Cox
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I'm not 100%, but I guess if the made for digital lens is designed for a crop sensor, then the circle of light illuminated at the rear of the lens will be designed to cover the crop sensor. This being smaller than a full frame 35mm film (not sure what that element is called...)errm... frame 
, will induce vignetting.
, will induce vignetting.
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Top marks above! Only with modern cameras they automatically detect the image circle and so a crop lens on a full frame body does not give vignetting - but the camera does become a crop sensor one, it trims in camera in other words to fit the coverage of the lens attached.
Clever, n'est pas.
Clever, n'est pas.
H
Holden Caulfield
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At aperture values above (F8 + ) this is because ‘digital’ lenses are made be used on APS-C sensors , which is are considerably smaller than 35 mm standard film which measures 36×24 mm. APS-C sensor sizes range from 20.7×13.8 mm to 28.7×19.1 mm.
As the aperture closes down it attenuates light which produces a vignette effect on a 36×24 mm sensor (dark edges), even with aspheric lenses which are designed to transfer light in a more parallel wave form the exit lens or rear element does not full cover a full frame sensor thus you get a light fall off.
H
Holden Caulfield
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I have never come across this, as which camera does this ?
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Not true. Aperture has nothing to do with image circle, which is the correct answer to this question (as posted in reply #2).
You can fit DX lenses to a full frame Nikon and it will adjust the sensor to the smaller format, but the equivalent lenses for Canon, EF-S, will not actually fit their full frame models.
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We have had vignetting with the D3 and the sigma 10 20mm and Nikon 17-50mm(designed for crop sensor) so it doesn't automaticly switch to dx format from full frame. Wayne
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It doesn't work with all lenses, but it does with most. It ought to work with the Nikon 17-55, unless you disabled the option.
Not quite true. See this.
Except the question is about film cameras, and film cameras obviously can't do this.
The short answer is that lenses designed for use only on crop digital bodies will cast an image circle big enough for the smaller sensor, which is about 24mm on the long end. 35mm film is 36mm on the long end. Therefore the image circle will be 12mm too small to provide good coverage on a film body. Some lenses might just work, because manufacturers tend to allow a little leeway.
The reason the lenses cast a smaller image circle is because they can. It's desirable because it results in cheaper manufacturing costs and a lighter, smaller lens.
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I don't get the link. How does f/number affect image circle in relation to the OP? The link is about vignetting
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Quote:
Originally Posted by HoppyUK
"Aperture has nothing to do with image circle"
I did say that. How is it wrong? Your link doesn't say otherwise.
I don't want to make a meal of it, but I don't understand how your initial comment has any relevance to the OP.
Originally Posted by HoppyUK
"Aperture has nothing to do with image circle"
I did say that. How is it wrong? Your link doesn't say otherwise.
I don't want to make a meal of it, but I don't understand how your initial comment has any relevance to the OP.
xSitara;1583619 said:The question is:
Why might you experience light 'fall off' when using a made-for digital lens on a film camera?
I am so stuck, there's nothing I can find about this in my revision papers. Do you guys have any ideas what I should put.?
Thanks
I think you need to read your papers a bit more thoroughly. There is also lots of informed information about this all over the web - just Google for it - it is SO easy to find this info these days without asking on a forum where you will get a variety of 'opinion' for something that is plain 'fact'!
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I reckon xSitara has much to contemplate given the contents of this thread and the one she started on POTN : http://photography-on-the.net/forum/showthread.php?t=701288
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The first paragraph of my response didn't have any relevance to the OP, but the last certainly did. That said, none of your post had anything to do with answering the original question so I'm not sure what your point is here.
You're saying that aperture has nothing to do with image circle. That isn't true. As you use a wider aperture the usable image circle decreases because the extreme corners of the field of view aren't visible from the entirety of the aperture/nodal point of the lens.