VideoJohn Posted June 7, 2023 Share Posted June 7, 2023 I've noticed something now working with my Hoya R72 filter. Using a modified camera or not, when I push and pull too far, I get this odd blotchiness in certain sections. Can anyone comment on what this is? I've been told it's related to wavelengths. Link to comment
ulf Posted June 7, 2023 Share Posted June 7, 2023 3 hours ago, VideoJohn said: I've noticed something now working with my Hoya R72 filter. Using a modified camera or not, when I push and pull too far, I get this odd blotchiness in certain sections. Can anyone comment on what this is? I've been told it's related to wavelengths. When you do that you reveal an unevenness that can be caused by many things. It can be due to minute variations in your sensor sensitivity that normally isn't visible. It can also be due to rounding errors in the RAW-conversion and post processing calculations. Also the working/processing colour-space can affect this. A narrow colour-space like s-RGB contain less available colours. That colour-space is used for publishing on the web, but not that suitable for editing. To minimize these effects you should shoot in RAW and use a good raw-converter to generate images for processing with 16-bit depth. Saving as a jpg should be done after the image is processed. Link to comment
VideoJohn Posted June 7, 2023 Author Share Posted June 7, 2023 5 hours ago, ulf said: When you do that you reveal an unevenness that can be caused by many things. It can be due to minute variations in your sensor sensitivity that normally isn't visible. It can also be due to rounding errors in the RAW-conversion and post processing calculations. Also the working/processing colour-space can affect this. A narrow colour-space like s-RGB contain less available colours. That colour-space is used for publishing on the web, but not that suitable for editing. To minimize these effects you should shoot in RAW and use a good raw-converter to generate images for processing with 16-bit depth. Saving as a jpg should be done after the image is processed. This is from a RAW image, to be clear. Link to comment
ulf Posted June 7, 2023 Share Posted June 7, 2023 47 minutes ago, VideoJohn said: This is from a RAW image, to be clear. Is it also edited in RAW or a high resolution format like a 16-bit TIFF? Link to comment
VideoJohn Posted June 7, 2023 Author Share Posted June 7, 2023 27 minutes ago, ulf said: Is it also edited in RAW or a high resolution format like a 16-bit TIFF? Adobe Camera RAW off the SD card for a .cr2 file. Link to comment
ulf Posted June 7, 2023 Share Posted June 7, 2023 Some types of filters give quite different levels for each of the RGB-channels. I do not think the R72 though, but instead rather low colour saturation. That is the reason for "pushing and pulling too far" Maybe it might be worth trying a different RAW-converter. They are not made the same in Raw-conversion routines. If the source of the problem is due to the way the values are calculated during the conversion, different converters use different algorithms and precision in their internal math routines. What type of computer/OS are you using? Link to comment
Andy Perrin Posted June 7, 2023 Share Posted June 7, 2023 Yeah, I agree with Ulf - try a different RAW converter first. Make sure the color space is something like ProPhoto or at least Adobe RGB (1998). There is also the kind of advice typified by the old joke, “Doctor, every time I do *this* with my arm, it hurts!” “Then stop doing that!” Just work within the limitations of the equipment. Link to comment
Nate Posted June 8, 2023 Share Posted June 8, 2023 Another thing also John, when I used some denoisers, I got the blotchy pattern too. It was really noticeable in astro shots Link to comment
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