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09-13-2008, 07:05 PM   #1
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Focal Length Comparison Tools

Ever wondered how the field of view changes for different focal lengths?

Canon USA Consumer Products - EF Lenses 101 - Focal Length Comparison
Focal length comparison tool, Tamron USA
http://imaging.nikon.com/products/imaging/lineup/lens/simulator/index.htm


Last edited by k100d; 12-15-2009 at 07:39 PM.
10-27-2008, 02:40 PM   #2
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Perspective Distortion in Portraits
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10-27-2008, 03:36 PM   #3
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Tamron has something similar on their website:

Focal length comparison tool, Tamron USA
10-27-2008, 03:37 PM   #4
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yup it's in the original post
but just added the portrait one i found while lurking on DPR. that was pretty cool

10-27-2008, 05:26 PM   #5
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QuoteOriginally posted by k100d Quote
Perspective Distortion in Portraits
Untitled Document
It seems to me this is more about the distortion levels in the specific lenses this person used than it is about perspective distortion. The only way to do this test would be with lenses that have similar image quality and no barrel or pincushion distortion. That's not something most people would have access to.
10-27-2008, 05:38 PM   #6
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QuoteOriginally posted by audiobomber Quote
It seems to me this is more about the distortion levels in the specific lenses this person used than it is about perspective distortion. The only way to do this test would be with lenses that have similar image quality and no barrel or pincushion distortion. That's not something most people would have access to.
are we looking at the same thing? that site only talked about perspective distortion for portraits.
10-27-2008, 06:54 PM   #7
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QuoteOriginally posted by audiobomber Quote
It seems to me this is more about the distortion levels in the specific lenses this person used than it is about perspective distortion.
I'm not sure where you got that idea - as far as I could tell, it's *all* about differences in perspective caused by moving closer in or further away in order to fill the frame at different focal lengths. Except for the 24mm and 19mm lenses, it's extremely unlikely any of the lenses involved would have had enough barrel/pincushion distortion to affect the results. These are pretty much exactly the differences one sees from changing position *only*. Although it seems they cheated a bit with the wide angle lenses by having the model change her head position and expression slightly, making the pictures even less flattering.
10-28-2008, 06:24 AM   #8
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QuoteOriginally posted by k100d Quote
are we looking at the same thing? that site only talked about perspective distortion for portraits.
I know... lens distortion isn't mentioned at all, and that's what bothered me. If I did this test using my 18-250mm, would the results be valid? It has 4% barrel distortion at 18mm and 1% pincushion at the long end. I would like to know how lens distortion was accounted for in the protraits.

Anyway, I agree with you, this graphic example of perspective distortion is interesting. It's a real eye-opener.


Last edited by audiobomber; 10-28-2008 at 06:32 AM.
10-28-2008, 06:37 AM   #9
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QuoteOriginally posted by Marc Sabatella Quote
Except for the 24mm and 19mm lenses, it's extremely unlikely any of the lenses involved would have had enough barrel/pincushion distortion to affect the results.
It depends on the specific lenses used. If they used zooms for these tests, it's bound to skew the results. Even a 35mm prime could easily have .5% barrel distortion. Comparing it to a longer lens with 1%+ pincushion distortion would add to the perceived change. I just think that lens distortion should at least have been mentioned.

Last edited by audiobomber; 10-28-2008 at 09:23 AM.
10-28-2008, 08:57 AM   #10
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QuoteOriginally posted by audiobomber Quote
It depends on the specific lenses used. If they used zooms for these tests, it's bound to skew the results. Even a 35mm could easily have .5% barrel distortion. Comparing it to a longer lens with 1%+ pincushion distortion would add to the perceived change. I just think that lens distortion should at least have been mentioned.
barrel/pincushion distortion affects photos where you can see straight lines as reference points. for people's faces, i don't think the effect will be very significant unless it's something like a fisheye. would be interesting to check tho just in case .
10-28-2008, 09:29 AM   #11
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QuoteOriginally posted by k100d Quote
barrel/pincushion distortion affects photos where you can see straight lines as reference points. for people's faces, i don't think the effect will be very significant unless it's something like a fisheye. would be interesting to check tho just in case .
I haven't ever tried to separate lens distortion from perspective. All I know is, this barrel distortion would distort someone's face.

10-28-2008, 09:49 AM   #12
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QuoteOriginally posted by k100d Quote
yup it's in the original post
but just added the portrait one i found while lurking on DPR. that was pretty cool

Doh! Sorry about that! For some reason I looked at your post and just didn't see it. I'll go have a timeout now.

10-28-2008, 09:54 AM   #13
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QuoteOriginally posted by audiobomber Quote
I haven't ever tried to separate lens distortion from perspective. All I know is, this barrel distortion would distort someone's face.
Only if you're shooting a true "blockhead"

Otherwise, you'll never notice this at all in the real world.
10-28-2008, 01:53 PM   #14
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QuoteOriginally posted by audiobomber Quote
I haven't ever tried to separate lens distortion from perspective. All I know is, this barrel distortion would distort someone's face.
An interesting experiment would be to load this image into your favorite image processing application, correct the distortion using the tools provided, note the settings used, then apply those same settings in reverse to the portrait samples to see how much of a difference. I'm still guess the difference would be minimal compared to the perspective - but here at least would be a way to test that theory...
10-28-2008, 05:04 PM   #15
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QuoteOriginally posted by Marc Sabatella Quote
An interesting experiment would be to load this image into your favorite image processing application, correct the distortion using the tools provided, note the settings used, then apply those same settings in reverse to the portrait samples to see how much of a difference. I'm still guess the difference would be minimal compared to the perspective - but here at least would be a way to test that theory...
If I corrected the garage door, wouldn't I be correcting the perspective distortion also? The photo was taken with the 18-250mm at 18mm. If I take that same photo with the 16-45mm, it will not look nearly as bad because the 16-45 has lower inherent distortion at the same focal length.
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