Judging a lens

mercphoto

What is a good way to judge a lens? This is what I want to do: figure out, for each of my lenses, what aperture range produces the best image -- where does it fall off (on both ends). I plan to use a tri-pod, remote shutter release, probably mirror-lock-up as well, and a stationary object. But should it be a flat object (printed piece of paper?) should it be a 3D object? I'm not wanting to judge depth of field, just sharpness across the frame.

I'm leaning towards a printed sheet of paper. I'm guessing a mixture of text and line graphics?

Thanks.

dkapp

Another good judge of a lens is the color reproduction. I've never done this with any of my gear, but I think the smugmug test color sheet would be perfect for something like this?



A larger version can be found at this link:
http://www.smugmug.com/help/print-color

Just scroll towards the bottom.

Let me know what you think.
Dave

wxwax

What are you trying to measure. Sharpness? Eveness of light across the entire frame (no vignetting?) Color saturation? Dunno, you might need more than one test card to get all that and whatever else folks test for.

pathfinder

mercphoto wrote:

What is a good way to judge a lens? This is what I want to do: figure out, for each of my lenses, what aperture range produces the best image -- where does it fall off (on both ends). I plan to use a tri-pod, remote shutter release, probably mirror-lock-up as well, and a stationary object. But should it be a flat object (printed piece of paper?) should it be a 3D object? I'm not wanting to judge depth of field, just sharpness across the frame.

I'm leaning towards a printed sheet of paper. I'm guessing a mixture of text and line graphics?

Thanks.

I always thought shooting an evenly lit shaded brick wall was a good subject for this kind of study. Like you said - tripod, timer, Mirror LU, make sure the film plane is parallel to the subject plane. Lots of straight lines to display pin cushion and barrel distortion. Easy to judge sharpeness at center versus edge as the image is the same all across. Can't tell much about color with this though.

But Norman Koren a retired engineer and photgrapher deluxe has spent a lot of time thinking and writing about this subject as you can see here. He may offer more detail than you are prepared for though.
http://www.normankoren.com/Tutorials/MTF5.html

He offers some nice image files for lens test subjects also.

His webste is a veritable fountain of knowledge if you can follow the math.