Emulating a different focal length?

Sometimes I find myself having to take pictures with a given lens

merely because it's on the camera and I don't have time to change for

a more suitable optic. Case in point, taking tight portraits with a

50mm lens on a 35mm camera when I would prefer to use the more

traditional 85 to 100 (or even 135) lens. Other times, I capture a

group of people with a 24 or 28 (in 35mm) and find myself disliking

the sometimes exaggerated "stretching" of the people furthest from

the center of the frame and would like to tighten perspective to that

of a 35mm or even 50mm lens. Can these perspective changes be made

digitally? I know that such things as tilts can so be corrected. I

have Photoshop and plan to get Picture Windows as well.

 

Thanks.

 

Alex

The differences perspective effects between longer focal length and normal

and shorter focal length lenses result from the distance the camera is from

the subject, So stand back from your subject and then crop later. There

maybe other ways to do this, but that is the most straight forward way ican

think of.<P> I can't see any reason to get Picture Windows in addition to

Photoshop, can you explain why you see a need to have both?

Ellis is right on. Perspective is only determined by subject to camera distance. Different lenses

only provide different angles of view, except tor the distortions created by extremely short focal

lengths. This actually makes it easier to control perspective with only one lens. Simply step

forward or back, if you can. This de-bunks the popular myth of phrases such as 'the

perspective of a lens'.

Generally speaking the two previous responses are exactly right - especially in the range you're asking about - slight wide-angle to telephoto.

 

It's possible to ADD some wide-angle or fisheye distortion using Photoshop's "pinch" or 'polar coordinates' or 'spherize' filters - not really duplicating what a real lens would do, but getting something of the 'look'.

 

Taking OUT wide-angle 'distortion' is probably close to impossible except for straight-line architectural-type stuff (the equivalent of tilting the easel under an enlarger to straighten converging lines).

 

By using layers and doing something along the lines of cutting out your main subject and dropping it into a blurred background from another frame (or a 'gaussian blurred' background) you can probably make a final image that looks vaguely like it was shot with a longer lens - but the perspective in the main subject itself (ie. relationship of nose size to ears, etc.) will still be that delivered by the original lens/camera-to-subject distance. Those folks in the corner of the 24mm frames will ALWAYS look stretched.

Your question got me to playing around: herewith a 35mm-lens original (left)converted to a 90mm (maybe even 180mm) portrait (right). I don't claim to be the world's best retoucher, though. Technique roughly as described in the last paragraph of my previous answer.