jbl Posted August 22, 2015 Share #1 Posted August 22, 2015 Advertisement (gone after registration) With the original MM, Leica published a chart of the sensor’s spectral sensitivity. I can’t seem to find one for the M246 CMOSIS sensor. Has anyone seen one? Anecdotal observations so far… Open shade with a yellow (#8) filter is around f/4, 1/250s, ISO 1000 (EV11) so at least at ISO 1000, the effective ISO is more like 250. -jbl Link to post Share on other sites More sharing options...
Advertisement Posted August 22, 2015 Posted August 22, 2015 Hi jbl, Take a look here m246 spectral sensitivity. I'm sure you'll find what you were looking for!
dante Posted August 31, 2015 Share #2 Posted August 31, 2015 Here's what I'm guessing will be a more helpful view (I own a complete set of B+W filters, so I was able to test this), which is in daylight shot on 90% reflectance neutral media (trial 1 is diffuse sunlight; trial 2 is bright sunlight). The scale is in PS levels, from the DNG, center-of-frame. I set the exposure to 320 ISO, manual setting such that no filter clipped white. Not a perfect test, but close enough. Understand that color contrast filters do not make hard cuts (as would be used in a spectrographic analysis), so things look a little different from a basic sensitivity chart. This infers the sensitivity. The reason why your yellow 8 looks so powerful is that open shade has a lot of blue light in it. For neutral-colored objects, the yellow 8 is actually the most transparent filter available (except to blue light). A lot of shots with the M typ 246 and orange and red filters look muddy, and that is not a surprise. This chart is mine; not for further reproduction. Dante Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/249209-m246-spectral-sensitivity/?do=findComment&comment=2879593'>More sharing options...
jbl Posted August 31, 2015 Author Share #3 Posted August 31, 2015 That's incredibly helpful, thank you! Link to post Share on other sites More sharing options...
dante Posted August 31, 2015 Share #4 Posted August 31, 2015 This would obviously not be representative of colored objects, but it tells you what you have to do to get the neutral ones to the exposure you want. I really want to do something like this with focus shift, which seems to be an issue with some lenses and filters. D Link to post Share on other sites More sharing options...
BjarniM Posted September 16, 2015 Share #5 Posted September 16, 2015 Here's what I'm guessing will be a more helpful view (I own a complete set of B+W filters, so I was able to test this), which is in daylight shot on 90% reflectance neutral media (trial 1 is diffuse sunlight; trial 2 is bright sunlight). The scale is in PS levels, from the DNG, center-of-frame. I set the exposure to 320 ISO, manual setting such that no filter clipped white. Not a perfect test, but close enough. Interesting. I'm not sure if i interpret the chart right. What's the unit on the Y-axis? What's it representing? Link to post Share on other sites More sharing options...
dante Posted September 22, 2015 Share #6 Posted September 22, 2015 Interesting. I'm not sure if i interpret the chart right. What's the unit on the Y-axis? What's it representing? Absolute level returned by Photoshop from the default-rendered RAW file (0-255), set so that the white target clipped as closely to 255 as possible. I have also changed these to log sub 255 charts here: https://themachineplanet.wordpress.com/2015/09/16/the-leica-monochrom-typ-246-and-filters/ So that you can see how the shapes compare to other media. Dante Link to post Share on other sites More sharing options...
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