DoF - straight or curved?
Bend The Light
Registered Users Posts: 1,887 Major grins
I was just looking through some old images, and this one taken with a MF Vivitar 90mm macro, at 1:1.
I noticed the thin "focal plane" is curved.
Is this right, and the focal plane is actually curved, or is it distortion which is not so evident in other lenses or something?
Unidentified dragonfly at Ynis-Hir 2 by http://bendthelight.me.uk, on Flickr
Thanks.
I noticed the thin "focal plane" is curved.
Is this right, and the focal plane is actually curved, or is it distortion which is not so evident in other lenses or something?
Unidentified dragonfly at Ynis-Hir 2 by http://bendthelight.me.uk, on Flickr
Thanks.
0
Comments
To verify, shoot a flat target (with the camera squared to the target) using a macro rail, or at least using a tripod with a crank stem, and capture a number of distances from the subject. You should see different "sections" of the flat subject matter exposed and sharp at different distances from the subject to confirm the field curvature.
Moderator of the Cameras and Accessories forums
Yes, that's what I thought. So the focal plane is not a plane at all...more a Focus Locus!
There are flat field lenses, commonly found in film duplication applications, and many more common lenses are "relatively" flat.
Field curvature occurs when the lens is not corrected for field curvature. Many/most lenses are at least partially corrected for field curvature. When you test your Vivitar 90mm macro against a flat subject and vary the shooting distance, you'll have a better idea of the extent of any field curvature in that lens.
Moderator of the Cameras and Accessories forums
14-24 24-70 70-200mm (vr2)
85 and 50 1.4
45 PC and sb910 x2
http://www.danielkimphotography.com
As far as I remember, and judging by other photographs taken at the same time, the wood is not curved...it is 3in x 4in timber railings and so all the same in all the railings in that wetlands area.
If you notice the forward facing wings of the insect follow the curve of focus, too...not sure that would happen if the focal plane was flat as it theoretically should be.