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Discussion Starter #1
Hi All,

An interesting discrepancy came up in a fake busters thread attempting to authenticate a watch.

The image on the left comes from the Omega website, though there is some question whether it is a photo or a CAD rendering. On the right is a photo of the watch in question.

Of particular interest are the lugs, namely how they differ so much in length despite the bezel being almost exactly the same size in both images.

Are there optical distortions or image processing that would explain the differences? Could these be photos of the same watch?

Aquaterra Quartz.jpg
 

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If the photo on the right is taken near the watch with a wide angle lens (cell phone camera is good example) then it would have a certain amt of distortion that could in theory account for what you're seeing. It would also taper the width of the bracelet to some degree which also appears to be happening. I can't say that's actually occurring here but it's possible.

This effect is more more pronounced by moving closer to the subject with a shorter focal length lens.

It's the same principle that you see over and over where people take wrist shots (with cell phones) and the watch looks bigger on the wrist than it does in real life.

If the picture on the right is rendered then it would seem to be rotated a bit because the top lugs look shorter than the bottom lugs. (The top red and blue lines are closer together than the bottom red and blue line.)
 

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consider this...

These two pics are of the same watch on my wrist. The 1st pic is taken close to the watch with a (wide angle) cell phone camera. The second pic is taken further away with the same cell phone camera.



The next pic is the same exact pic shown 1st above... but the last pic below is the 'further out' pic cropped so that my wrist and hand appear roughly congruent.



This illustrates how a wide angle lens makes things in the middle of the frame appear larger, and the distortion wraps everything else in the pic back so that the rest of the pic looks smaller.

What I'm trying to say is that if someone took the Omega pic above on the right with a wide angle camera and very close to the watch, that it could make the face of the watch disproportionately larger than the lugs and bracelet. In my pics the effect is really with the whole watch vs the wrist. Same principle.
 

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Discussion Starter #4
Thanks nolte, great post. Could well explain the small lugs. I expect the photo was taken up close with a cell phone as you suggest.

Is there a name for this effect?
 

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I've always just heard it called perspective distortion. There are probably more terms and specific types of it that I am ignorant of.
 

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This illustrates how a wide angle lens makes things in the middle of the frame appear larger, and the distortion wraps everything else in the pic back so that the rest of the pic looks smaller.
Actually, no. It is true that many watch pictures look like that, but it is only because only the watch is relatively close to the camera and the background (even the wrist) is relatively far away, thus looks small. If you took a picture of something flat (tabletop filled with watches, say), the watches in the corners would look elongated and larger than they should, not smaller. That would be the real W-A distortion, called rectilinear distortion. The "distortion" which comes from taking the pictures too close is not the fault of the lens, but just the normal perspective when a watch is looked at close enough. Even without a camera, with bare eyes.

Another thing, wide-angle lens does not do this distortion (lugs looking smaller/bigger), it is only the perspective which depends ONLY on the distance the photograph is taken from. That was already demonstrated above. Why this appears in W-A photos? Because they are taken too close to the subject (watch) because otherwise the watch would appear too small in the picture. If the picture is taken from greater distance and enlarged, it would look exactly like a shot taken with a short telephoto lens from the same spot, but of course the quality would suffer. The perspective would be identical, though, because that depends ONLY on the distance, not focal length.
 

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Yeah you're right of course I hadn't thought that out properly.

The distance to the subject makes the watch seem larger in spite of any distortion.

I dunno if the OP's pic is affected enough by proximity to the lens to account for the lugs.
 

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Thanks nolte, great post. Could well explain the small lugs. I expect the photo was taken up close with a cell phone as you suggest.

Is there a name for this effect?
Lena distortion , barrel distortion are the common ways to refer to it.
 

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Also it should be pointed out that now days it is very easy to fix if you’re working with a RAW format of the picture and you have any of the common editing softwares as the effect is well
Documented on a “per lens” basis. So it can be fixed if you download that lens profile to your editing software. You can also use it to your benefit to make objects look thinner or wider ;)
 

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Discussion Starter #10
Good stuff, thanks to everyone who has responded.

Vakane - I am planning to photograph some watches with a DLSR. I hadn't thought about correcting for distortion. Could you recommend open source editing software? I'm not sure people snapping photos with their cellphones would take this step but I'm interested to see the difference.
 

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Good stuff, thanks to everyone who has responded.

Vakane - I am planning to photograph some watches with a DLSR. I hadn't thought about correcting for distortion. Could you recommend open source editing software? I'm not sure people snapping photos with their cellphones would take this step but I'm interested to see the difference.
Your DSLRs software should do(should be provided to you Ina cd and can also be downloaded from the makers webpage).

But photoshop or light room both carry the tool as well as the Apple software which now allows to edit RAW files.
 
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