[BUG?] Invert on negative causes massive overexposure

Bugs & Suggestions
Post Reply
neilmwhite
Posts: 10
Joined: Tue Jan 24, 2012 2:14 pm
operating_system: Windows 7 Home Premium
System_Drive: C

[BUG?] Invert on negative causes massive overexposure

Post by neilmwhite »

Hi,

From time to time using Bibble, I would convert a 35mm colour film negative which had been captured using a slide/neg converter lens attaced to my DSLR to RAW (DNG)

One of the steps to do this was using the "INVERT" feature.

I am trying to replicate this process in ASP, but everytime I check the INVERT box, the whole image becomes massively over exposed. It's possible to recover some of the detail using the Exposure slider (moved to the highest possible value), but in so doing, buch of the intermediate tone is lost.

Any ideas on what is wrong? I didn't have this problem with Bibble 5 Pro. (Yes I realise that quite a bit of work is required to remove the blue cast caused by the conversion of the orange negative, but I have ways to handle this - but the tonal detail was pretty much retained).

Neil
neilmwhite
Posts: 10
Joined: Tue Jan 24, 2012 2:14 pm
operating_system: Windows 7 Home Premium
System_Drive: C

Re: [BUG?] Invert on negative causes massive overexposure

Post by neilmwhite »

Actually - it may be just a degree of change compared to Bibble.

I've had a look at some of the negative conversions I did with Bibble and I note that I did have to move the exposure considerably to the right after doing the inversion.

However, the latest negatives I have copied and am trying to process with ASP seem to require such extreme exposure adjustment it is difficult to refine the tonal range enough.

To give an indication of the comparison - Please click on the links to screenshots of the same RAW images in the browser and the effect that ASP seems to have on the Inverted images. The effect is similar whether using a file that was previously processed in Bibble or a new one.

Bibble
http://neilsplace.dyndns.org/misc/image ... e-Negs.jpg

ASP
http://neilsplace.dyndns.org/misc/images/Asp-Negs.jpg

Neil
grubernd
Posts: 248
Joined: Thu Jan 12, 2012 8:17 pm
operating_system: Linux
System_Drive: N/A
Location: Graz, Austria

Re: [BUG?] Invert on negative causes massive overexposure

Post by grubernd »

try using the grey rectangle in the curves tool before doing any other adjustments. it should work way better than the exposure correction for this, since the negative has also a different gamma than a positive. this effect gets pronounced by the raw-optimized toolchain. pull the grey triangle down and work from there.
Bibble since 2004. Aftershot until 2020. From then on darktable.
Post Reply