+ Camera Raw Feature Requests +

If you think none of your lenses exhibit vignetting, try the following:
1) Attach any of your lenses to a camera with a full frame sensor or a film body
2) Shoot the sky wide open and at the shortest focal length
3) Look at the image to see if there is any darkness in the corners that is inconsistent with the rest of the image
Most reviews in Popular Photography include a sentence such as:
"Light falloff left the corners by f/3.3." Since film bodies are becoming more rare, it only makes sense to include a tool that automatically corrects for this problem when the RAW image is processed on a computer.
The technology exists to make images better by correcting for vignetting. Why not take advantage of it?

If you have vignetting to that extent, get a decent lens. :D

>It would be great if the lens manufacturers would provide this information.

it certainly would. but I expect a public database of lens attributes to be collected and published before camera and lens manufacturers go out of their way to advertise some of their less than ideal qualities. ideally, for the photographer, your RAW editor would relay any XML data to a web site that looks up and verifies information about that specific lens. it may be information relating to known abberations, distortions, sharpness, age, and vignetting. the raw editor would then automatically fill in the blanks just like music CD's are catalogued on your computer.

the technology to do this cost-effectively has come out of the lab. there may be hope for the future ... :-)

>I am currently building a list of vignetting amount and midpoint values for various apertures and focal lengths for my lenses.

that's kewl. incidentally, this may differ for each camera model the lens is applied to --which would make it at least a 3D array, and possibly each lens revision --which would make it 4D.

Ian,

I meant avoided at the scanning stage (ahem).

Barry ...
>I've been wondering whether to photograph my slides and negatives in raw (at least sometimes) because of the time it takes to scan them in.

flat bed scanners are specifically designed to reproduce flat objects with very little distortion and film scanners offer very high resolution with extended dynamic range. ultimately these devices are best.

however, if you're looking for "good enough", it is possible to photograph your film.
suggested methodology:

1. take care to ensure the that film is parallel to the focal plane.
2. use a lens that will minimize abberations or distortions of any kind.
3. use a secure stabilizing device such as a tripod.

you might also consider an old slide copier attachment -either extension tubes or bellows attachment. ultimately, you're the final arbitrator of quality and if you're satisfied with the resolution, sharpness, and any abberations introduced along the way then it becomes an entirely subjective process but technically viable. :-)

regarding color casts, Ian has been one of the early web pioneers publishing sound scanning techniques--and a must read. i highly recommend visiting any of his pages.

Shangara ... What a simple but brilliant suggestion!

>Simply inverting a negative will produce orange casts. These casts can only really be avoided by using a special color profile for the negative type you are trying to copy.

Nope: from a 2002 tutorial - http://www.computer-darkroom.com/tutorials/tutorial_6_1.htm

That sounds like a good method. Thanks for the link, Mike.

Flipping the curve will create a blue/cyan cast, becaue of the orange mask.

Inversion of color negatives is easier to do in Photoshop, and not ACR.

There is a procedure discussed at the bottom of this page:
http://www.curvemeister.com/tutorials/what_ails_you/index.htm

Mike Russell

Hmm... Neither scanning nor photographing negatives are straightforward. Simply inverting a negative will produce orange casts. These casts can only really be avoided by using a special color profile for the negative type you are trying to copy.

Mat

Chris, are you photographing the negatives in raw? If so, what equipment are you using? And are you getting good results?

I've been wondering whether to photograph my slides and negatives in raw (at least sometimes) because of the time it takes to scan them in. I've already sometimes photographed prints rather than use a flat-bed scanner (which I don't have!)