Re: effect of lens length

[P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>]

>It seems to me that the original question here was, do you get the same image:
>>>>> if you crop an image taken with a 50 mm lens to the same part as
>>>>> an image taken with a 80 mm lens, and make them the same size - would
>>>>> you have the same thing as two pictures both taken with 80 mm lenses?
>
>But 3d-ers read this as, would this change
>>>the relationship of foreground and background objects.

That's because this is THE MOST IMPORTANT ISSUE.  If you do not solve this
one, then there is no reason to worry about the minor details:

>--aberrations, especially blur at edge (OK, cropping would reduce)
>--flatness of the image...pincushion, barrel, or other distortions
>--exposure, leading to film effects such as color balance, reciprocity
>--lens design

Which will only determine if the match is PERFECT instead of just good.

Regarding the DOF, that's another story but when you change the
magnification to match the two images you will see that the DOF is the 
same even though lenses of different FL were used.

>--don't longer f.l. shots have more 'cardboarding', less of a sculpted
>appearance to the objects?

That's a totally different story... I think the original question was
strictly in 2D. In 3D you have factors like seperation of the lenses and
viewing conditions that become important.

George Themelis


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