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suggestion: processing of color negative film scan

PostPosted: Sat Aug 04, 2012 6:01 pm
by WilfriedH
Sometimes I use my DSLR (Pentax k-r with a macro lens) to make a copy of a color negative (on a lightbox).
Up to now I process it with Photoshop Elements (PSE).
First I remove the color mask of the film by white balance, pointing with the selector (pipette tool) to an unexposed area of the film.
Then I invert the colors.
The result is already quite useable, but sometimes I'd like to further process it with sns-hdr.
But PSE allows saving with 8bit color depth only.
So it would be nice if the first two steps could be integrated into sns-hdr, so that the full precision of the raw image can be loaded in sns-hdr.
White balance is already available in sns-hdr, but not color inversion -- or have I overlooked this?
Wilfried
(registered user of sns-hdr home)

Re: suggestion: processing of color negative film scan

PostPosted: Thu Aug 16, 2012 1:48 pm
by den
Just curious... ...have you tried letting SNS-HDR RAW convert and tone-map the captured "color negative" Raw file with perhaps the Default preset; saving the resulting image as a 16 bit tiff [and perhaps with a sRGB color profile]... ...then do the Invert/Color Balance with your external editor?

The dis-advantage would be no intuitive 'custom' editing of SNS-HDR's presets but there was a time before 'digital' when post-processing color negatives was a common art.

Re: suggestion: processing of color negative film scan

PostPosted: Sun Aug 19, 2012 7:15 pm
by WilfriedH
A photo of a negative has three problems:
1.The orange mask of the negative film. The color temperature pipette tool can change the mask from orange to gray but not to white.
2.The film grain is intensified by SNS-HDR.
3.The remaining image has low contrast.

Current best settings (for one specific photo):
On loading, set noise reduction to 6 (problem 2)
Use the pipette tool to set orange to gray (problem 1).
Set brightness to 100% to change the mask from gray to white (problem 1, approximately).
Save as 16bit tiff. Use external editor to invert colors.

So before applying the tonemapping, a preprocessing is required:
Adding the inverse tone value of the orange mask so that the color of the mask gets white (problem 1). This cannot be done in the current version of SNS-HDR.
Noise reduction to remove the film grain (problem 2; in the current version the setting 6 is good).

The contrast enhancement (problem 3) should be automatic by the existing tone mapping.

Re: suggestion: processing of color negative film scan

PostPosted: Sun Aug 19, 2012 9:40 pm
by den
Thank for the further explaination... ...my curiosity is aroused!!!

Could you perhaps provide a screen shot of the captured 'color negative' SNS-HDR Raw conversion with the Default preset selected as it appears in the work space and no other edits...?

This is more a matter of my own curiosity and if you do not wish to pursue this, it is fine as well.

SNS-HDR does have 'Invert' capability by reversing the default diagonal curve of the RGB Curves "///", ie, raise the lower left end vertically to the upper left corner and lower the upper right end vertically to the lower right corner... ...changing the slope of the diagonal can increase or decrease contrast and Luminance white/black point clipping can be monitored while observing the 'white' portion of the Histogram near the display's left/right side verticals... ...one might also be able to turn a 'gray' color balance white in the case of 'negative' or black in case of a 'positive' [Invert] with an added RGB curve control point...

Re: suggestion: processing of color negative film scan

PostPosted: Tue Aug 21, 2012 4:48 pm
by den
To illustrate one possibility for SNS-HDR v1.4.22.1 color negative development:

(1) a simulated color negative image was created from a single CR2 file's embedded JPEG; film grain added; and 'Invert'-ed. This simulated image has less than full dynamic range and low contrast, low brightness, and dull color... ...and the simulated color negative image does not address possible needed geometry and/or color temperature (balance) corrections when taking a digital photograph of a color negative film strip back-lighted by a lightbox... ...nor the film strip frame that may be in-frame for the camera's capture...

Before/After:
capture_21082012_075312-1.jpg
capture_21082012_075312-1.jpg (98.58 KiB) Viewed 5502 times

(2) the simulated color negative image was SNS-HDR processed with a modified SOFT tone mapping preset because of the film grain; Invert'-ed with an increase in brightness/contrast using the single RGB Curve; increased High Lights saturation; and reduced sky image area Microdetails/Microcontrast...

The modified SOFT preset editing settings used:
SNS-HDR_editedSOFTpreset.jpg
SNS-HDR_editedSOFTpreset.jpg (61.23 KiB) Viewed 5502 times

...just exploring SNS-HDR possibilities with a photo realistic ambience... ...ask if there are questions...

...den...

Re: suggestion: processing of color negative film scan

PostPosted: Sun Aug 26, 2012 11:13 am
by WilfriedH
den, thank you for explaining.
However your settings seem complicated to me, moreover, to do it all manually would be a hazzle if processing several negative scans one after the other. I'd like something like a preset like for normal (positive) pictures.
I attach the raw file for experimenting with it.
The area of the lightbox around the film strip was covered with plain white paper so that the uncovered area did not bias the camera's exposure setting. The uncovered edges of the film perforation show that the distance setting was correct and that the grainyness of the picture is not a problem of the camera or lightbox with which the scan was made.
Wilfried

P.S.: I now additionally uploaded the scan made by the professional photo lab (IMGP1267dm-scan.jpg) and the DSLR scan edited with Photoshop (IMGP1267pse-k.jpg). It seems that the DSLR has problems with this low contrast picture.

Re: suggestion: processing of color negative film scan

PostPosted: Sun Aug 26, 2012 11:27 am
by Sebastian Nibisz
I will add the negation option in the next version.