Is NegaFix Useful?

[RogerMillerPhoto]

I'm starting to question if NegaFix is of any value. It's not even in the ballpark. I'm shooting Kodak Portra 160NC (medium format) in a studio with controlled lighting. It's properly exposed and processed by a professional lab. I scanned it (Polaroid SS120 on a PC with MS Me) using Ai to generate a raw 48-bit file. The scanner was IT8 calibrated and its profile was embedded in the 48-bit file. I then used HDR, but disabled calibration per Ian Lyons' revised tutorial. HDR used the Kodak Portra NC 6x6 profile. The "auto" feature of NegaFix wouldn't work because the image was of a model against a white background, so I manually adjusted the endpoints to clip the white background. The resulting image was extremely dark. The only solution was heavy adjustment of the curves (profile expert mode). I had better luck using a profile of "other" with a "linear" curve. It seems that the furnished profile was of little value. I'm better off starting from scratch and building my own profile. Am I misunderstanding something or doing something wrong, or are the NegaFix profiles worthless?

Roger Miller

[ilyons]

Robert,

First - the tutorial for "NegaFix" shows the CMS dialog with NO calibration facilities in use. The HDR tutorial was originally for postive type films. I have since added a few notes for negatives that might help clear up your confusion.

BTW: you do NOT want the scanner profile anywhere near the NegaFix data.

Next. If you want to scan a raw 48 bit file for later processing in HDR I would suggest that you "uncheck" the "Gamma for HDR" option in AI. The raw negative will then be a lot darker and will also contain no profile. However, it seems that doing this makes a big difference in how HDR with NegaFix interprets the image.

In HDR set the gamma gradation for your desired value and the CMS dialog as shown in the NegaFix tutorial. Alternatively (not yet confirmed by LaserSoft) you could set it for Internal (Monitor) = Auomatic and Internal = Adobe RGB? - but do NOT allow ANY scanner profiles to be used - they are NOT needed or desirable.

I think we need a spell checker - every time I read "my" posts I see more mistakes than I care to believe is possible

<font size=-1>[ This Message was edited by: ilyons on 2001-08-17 13:31 ]</font>

<font size=-1>[ This Message was edited by: ilyons on 2001-08-17 15:58 ]</font>

[ianders1]

Roger,

I'm also having some difficulty scanning in high key photographs (Medium Format Negs) with NegaFix. I don't have HDR, so I can't help you there, but it seems that manually adjusting the white and black point (those little sliders in NegaFix's Expert Dialog) seems to remedy the problem.

Also, for comparision, I went back to v5.2, and Epson TWAINPro (the crappy program that came with my scanner) to try the same scan - it was nearly impossible to get anything half decent. Let me know how it works out. for you,

-Ian

[RogerMillerPhoto]

I'm now starting to believe in NegaFix. I had a gamma problem. Here's what to do if scanning with Ai to create a raw 48-bit file on which HDR and its NegaFix will be used:

Scan with Ai as described in Ian Lyons' tutorial, "Basic steps for optimising hight-bit Scans." However, modify those instructions per Ian's post to this forum question above, namely, uncheck the "for HDR Ouptut" box (in "Options" in the "General tab) and, also, do not allow any scanner profiles. The scanner profiles can be eliminated by following Ian's tutorial on NegaFix in which he describes how to set up profiles and color management under the CMS tab in "Options." (Basically, just about everything is set to "none".)

Next, use HDR to prescan the file created by Ai. In HDR, set it up as described in Ian's "Basic steps for optimising hight-bit Scans" except the "Gamma-Gradation" should be set to 2.2 instead of 1.0 in the "General" tab of "Options." That change is evidently needed because the gamma "for HDR output" box in Ai was not checked earlier. I really don't know what I'm talking about now with respect to gamma, but I know it curred my problem by setting it to 2.2 and my image now isn't so dark and underexposed. At this point, I could have used NegaFix tools and the standard HDR tools to further correct and fine tune the colors, but at least I'm now in the ball park.

Ian, thanks for your help. I'd be lost without your tutorials and comments. So would a lot of other people.

<font size=-1>[ This Message was edited by: RogerMillerPhoto on 2001-08-18 08:58 ]</font>

[ilyons]

Robert,


you had me worried, I spent hours yesterday checking and rechecking every last ccombination and then modified the tutorials so that NegaFix users didn't feel left out

You must have missed the sentence:

>The "Gamma-Gradation" should be set for "1", however, if the image is a scanned negative this value should be set between "1.8" and "2.2".


Glad to see that all worked out in the end.