Overexposure

[chufi]

Hi, I'm scanning slides at 64bit HDRi to DNG as archives and having big overexposure problems. I am scanning slides of snow camping so there is a lot of white in the slide but it isn't blown out. I do a prescan, then adjust the gamma down so it looks reasonable (say 1.0 or . then scan. The scan is way overexposed compared to the preview the whole histogram is slammed to the right and the highlights are blown. I am doing all processing of the image in lightroom.

The scanner seems fine as I have scanned many other slides that are properly exposed that do not contain snow.
I've tried in 48 bit 'plain' mode, same issue.

Any thoughts on how to keep this from getting over exposed?

[LSI_Ketelhohn]

Dear customer,

The 48 Bit HDR format is an unprocessed archive format for our Archive Suite workflow.
These files are saved without any changes for later processing in SilverFast HDR Studio.

For most other workflows the normal 48 Bit format works better.

I have also forwarded your Post to our support center, because we most likely will need some sample images to help you further.

Kind regards,
Arne Ketelhohn.

[chufi]

Support People said something similar,though they said the DNG format was only intended for HDR Studio (doesn't come with my scanner) which doesn't seem right since adobe invented the DNG format and clearly knows how to read it.

I am trying to do archival format (which for me is DNG) and have the 'i' channel in there so if I want to I can do the scratch and dust removal at a later date, etc, etc. So using the 48->24 mode to make a jpeg isn't what I'm going for.

The 64HDRi scans work fine when I just need to boost the shadows but seem to totally fail for when the image is already exposed. Here are three screenshots - in Silverfast before scanning, then in lightroom after import and in lightroom after autotone. Sorry for the tiny images but the attachment size limit is just crazy small.

sliverfast.jpg (205.08 KiB) Viewed 1521 times

lightroom1.jpg (88.27 KiB) Viewed 1521 times

sliverfast.jpg (205.08 KiB) Viewed 1521 times

[LSI_Ketelhohn]

Dear customer,

The HDRi format is completely unprocessed.
Simply making it brighter will not produce correct results.
For these images the highlights and shadows must be set befor colorspace transformation and the gamma must be set to 2.2.
(the gamma in the images is 1.0).

The DNG format only makes sense for this kind of images, as it is intended for unprocessed "raw" data.

Kind regards,
Arne Ketelhohn.