Luminous Landscape Forum

Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: hauxon on March 20, 2009, 08:05:39 am

Title: Correcting WB in a film scan
Post by: hauxon on March 20, 2009, 08:05:39 am

I don't know if this is the right place for the post but anyway.....

I work with areal photographs witch are scanned from 10x10 inch LF film.  The scans result in a 30000x30000 pixel image (900MP).  Some of the older scans are way off in WB and need correction.  

With my DSLR I do processing in Lightroom and adjusting WB is easy.  I would however not dare to laoad a 900 megapixel image into LR.  I'd also like to batch process a series of images (from same flight).

Any ideas?

Best, Hrannar

Title: Correcting WB in a film scan
Post by: CBarrett on March 20, 2009, 09:11:34 am

Hi Hrannar,

I usually do that sort of move in Photoshop with a Curves Adjustment Layer, if they're not too far off.  You grab the curve for R,B or G and drag it down a little to reduce excessive cast in that range.  If the cast is comparable across many shots, and you're just trying to get in the ballpark, I don't see why you couldn't build a Photoshop Action to do it... I wouldn't be surprised if this much heavy processing on a repetitive basis caused some freeze-ups, tho...Those are some damn big files!

If you're not familiar with Actions, do a little investigation and learn how to build them.  It's really pretty easy and will save you tons of time for any repetitive tasks...   I have actions that step down my images from 39mp to web size in 10% increments to retain maximum clarity and Photoshop does all the work while I go warm up my coffee...

Hope this Helps,
Chris

Title: Correcting WB in a film scan
Post by: KevinA on March 20, 2009, 09:53:16 am

Quote from: hauxon

I don't know if this is the right place for the post but anyway.....

I work with areal photographs witch are scanned from 10x10 inch LF film.  The scans result in a 30000x30000 pixel image (900MP).  Some of the older scans are way off in WB and need correction.  

With my DSLR I do processing in Lightroom and adjusting WB is easy.  I would however not dare to laoad a 900 megapixel image into LR.  I'd also like to batch process a series of images (from same flight).

Any ideas?

Best, Hrannar

I think the size of the file is the problem, trying to do a batch of them will pull down most computers. You need some serious power for this. It might be easier and quicker to rescan them, I assume you do that in house? You will still need a hefty computer to keep things moving.

Kevin.

Title: Correcting WB in a film scan
Post by: hauxon on March 20, 2009, 11:57:16 am

Thanks for the relies.

The films in question may be buried down somewhere in storage.  We shoot in rolls of 500 frames per roll and finding offending sequences within a roll, shot in say 2002, may be VERY time consuming.  That's why we do not want to rescan.

We do have able multiprocessor 64-bit computers with lots of memory but Photoshop may be the weak link.  I'll give it a try over the weekend with a sequence of 10-15 images.

I did know of and use PS actions but didn't know of the batch action.  I did do a test (with a smaller image) using Curves and the results were pretty nice.  

Best, Hrannar