OpticFilm colour/brightness/iSRD problems? Read this first.
PostPosted: Sat Jun 09, 2012 8:11 am
Hi All,
I've discovered an issue which appears to affect many Plustek OpticFilm scanners. The problem can produce a variety of symptoms:
- Very dark or underexposed and posterised negative scans,
- Overexposed or bright slide scans,
- Strongly colour tinted scans when using Multi-Exposure,
- iSRD not working at all.
All of these are not subtle in appearance. The symptoms may occur sporadically, and may only appear every few scans.
I postulate that these problems are caused by a lag in the scanner lamp reaching its required power/luminosity.
To explain further: The brightness of the final scan is controlled by two variables: lamp power and exposure time. The longer the exposure time, the longer it takes to scan. The lamp power may have only one, constant value, which can be compensated with a varying exposure time. I believe that, under certain conditions, the lamp takes too long to reach the desired output. The hardware may be designed to perform certain actions according to timing that doesn't take this extra warm up time into account. I believe one of those actions is an initial, internal, low resolution pre-scan (not to be confused with the SilverFast Prescan) that determines the optimal lamp brightness and exposure time. If during this initial scan the lamp is not bright enough, the scanner will increase the exposure time to compensate for the lack of light. You can detect this when scanning a well exposed image at high resolution. The full scan will take much longer to complete, and you will hear the internal motor stutter as is slowly moves. This can happen sporadically, so sometimes this may occur only for the full scan or the iSRD scan or the Multi-Exposure scan, or a combination of these. This combination will result in an unexpected image being sent to SilverFast, which will process it as if nothing went wrong - resulting in one of a number of problems, depending on which exposure the lamp lag affected the pre-scan. This problem doesn't occur for everyone, which may be because of different components being sourced for different scanners (even of the same model) or because of a difference in the conditions under which you're scanning (e.g. room temperature) or both.
The solution
The solution is to warm up your lamp/the electronics. Perform a Prescan 2-3 times in SilverFast and immediately do the scan. If it is slow, cancel it immediately and then try scanning again. This has consistently worked for me so far. You shouldn't need to do this if you're scanning continuously. But if you stop for a while the 'ritual' will have to be repeated again.
All this sounds like a hardware issue - and I'm just guessing here. But you could substitute the issues of timing within the scanner with something to do with the scanner driver SilverFast uses, since SilverFast can control the exposure time.
I hope this post is approved, because I believe it may be of much help to others.
Regards,
-A
I've discovered an issue which appears to affect many Plustek OpticFilm scanners. The problem can produce a variety of symptoms:
- Very dark or underexposed and posterised negative scans,
- Overexposed or bright slide scans,
- Strongly colour tinted scans when using Multi-Exposure,
- iSRD not working at all.
All of these are not subtle in appearance. The symptoms may occur sporadically, and may only appear every few scans.
I postulate that these problems are caused by a lag in the scanner lamp reaching its required power/luminosity.
To explain further: The brightness of the final scan is controlled by two variables: lamp power and exposure time. The longer the exposure time, the longer it takes to scan. The lamp power may have only one, constant value, which can be compensated with a varying exposure time. I believe that, under certain conditions, the lamp takes too long to reach the desired output. The hardware may be designed to perform certain actions according to timing that doesn't take this extra warm up time into account. I believe one of those actions is an initial, internal, low resolution pre-scan (not to be confused with the SilverFast Prescan) that determines the optimal lamp brightness and exposure time. If during this initial scan the lamp is not bright enough, the scanner will increase the exposure time to compensate for the lack of light. You can detect this when scanning a well exposed image at high resolution. The full scan will take much longer to complete, and you will hear the internal motor stutter as is slowly moves. This can happen sporadically, so sometimes this may occur only for the full scan or the iSRD scan or the Multi-Exposure scan, or a combination of these. This combination will result in an unexpected image being sent to SilverFast, which will process it as if nothing went wrong - resulting in one of a number of problems, depending on which exposure the lamp lag affected the pre-scan. This problem doesn't occur for everyone, which may be because of different components being sourced for different scanners (even of the same model) or because of a difference in the conditions under which you're scanning (e.g. room temperature) or both.
The solution
The solution is to warm up your lamp/the electronics. Perform a Prescan 2-3 times in SilverFast and immediately do the scan. If it is slow, cancel it immediately and then try scanning again. This has consistently worked for me so far. You shouldn't need to do this if you're scanning continuously. But if you stop for a while the 'ritual' will have to be repeated again.
All this sounds like a hardware issue - and I'm just guessing here. But you could substitute the issues of timing within the scanner with something to do with the scanner driver SilverFast uses, since SilverFast can control the exposure time.
I hope this post is approved, because I believe it may be of much help to others.
Regards,
-A
