Simon Blackley Posted May 19, 2022 Share #1 Posted May 19, 2022 Advertisement (gone after registration) I shoot in manual mode, either at ISO 100 or in auto-ISO. When in auto-ISO, I notice that the camera never drops the ISO below 200, even when there is plenty of light. Can anyone explain what's going on? Link to post Share on other sites More sharing options...
Advertisement Posted May 19, 2022 Posted May 19, 2022 Hi Simon Blackley, Take a look here Q2 monochrom auto-ISO . I'm sure you'll find what you were looking for!
jaapv Posted May 19, 2022 Share #2 Posted May 19, 2022 That is correct as ISO 100 is a pull value with reduced dynamic range in the highlights. Link to post Share on other sites More sharing options...
JimKasson Posted May 19, 2022 Share #3 Posted May 19, 2022 8 hours ago, jaapv said: That is correct as ISO 100 is a pull value with reduced dynamic range in the highlights. That is surprising to me. Here's what I get for EDR vs ISO on my Q2M. 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/332586-q2-monochrom-auto-iso/?do=findComment&comment=4438064'>More sharing options...
jaapv Posted May 19, 2022 Share #4 Posted May 19, 2022 well, in that case I have no explanation. Your measurement is confirmed by PhotonstoPhotos 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/332586-q2-monochrom-auto-iso/?do=findComment&comment=4438067'>More sharing options...
Simon Blackley Posted May 19, 2022 Author Share #5 Posted May 19, 2022 Surely Leica can tell us what the base ISO is, ffs? Link to post Share on other sites More sharing options...
JimKasson Posted May 19, 2022 Share #6 Posted May 19, 2022 It turns out there is some funny business at ISO 100. It looks like Leica is chopping off the right side of the histogram before nominal full scale. This is a different techniques than SOny, Nikon, and Fuji use for their fake ISOs. 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/332586-q2-monochrom-auto-iso/?do=findComment&comment=4438149'>More sharing options...
JimKasson Posted May 19, 2022 Share #7 Posted May 19, 2022 Advertisement (gone after registration) I've looked into this situation some more, and it appears that ISO 100 is a fake ISO on the Q2 Monochrom. https://blog.kasson.com/leica-q2-monochrom/leica-q2-monochrom-edr-fake-iso/ Link to post Share on other sites More sharing options...
junix Posted May 20, 2022 Share #8 Posted May 20, 2022 This data is mentioned in the Technical Data sheet of the Q2M "Dynamic range 13 aperture stops for basic ISO 200", screen shot from the pdf: 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! Now you can shoot in Manual mode at ISO 200 Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! Now you can shoot in Manual mode at ISO 200 ' data-webShareUrl='https://www.l-camera-forum.com/topic/332586-q2-monochrom-auto-iso/?do=findComment&comment=4438238'>More sharing options...
JimKasson Posted May 20, 2022 Share #9 Posted May 20, 2022 (edited) I don't get anywhere near 13 stops of DR at ISO 200. I get about 12 stops for EDR. What are Leica's test conditions? Edited May 20, 2022 by JimKasson Link to post Share on other sites More sharing options...
JimKasson Posted May 20, 2022 Share #10 Posted May 20, 2022 (edited) 25 minutes ago, JimKasson said: I don't get anywhere near 13 stops of DR at ISO 200. I get about 12 stops for EDR. What are Leica's test conditions? Bill Claff gets the read noise at ISO 200 as 3.117 LSBs. https://www.photonstophotos.net/Charts/RN_ADU.htm#Leica Q2 MONOCHROM_14 2*log2(16383/3.117) = 12.36 stops. Edited May 20, 2022 by JimKasson Link to post Share on other sites More sharing options...
Ba Erv Posted May 20, 2022 Share #11 Posted May 20, 2022 I’ve been confused about this for months. Sean Reid also mentioned in his testing that base ISO was around 160…which doesn’t exist on the camera. For me the battle with this camera has been preserving the highlights while monitoring the histogram. The highlight spike on the histogram seems to go from midrange to off with merely a 1/3 change of exposure compensation between ISO 100 vs 200. There doesn’t appear to be any smooth transition. Someone educate me, pleeeeese! Link to post Share on other sites More sharing options...
JimKasson Posted May 20, 2022 Share #12 Posted May 20, 2022 (edited) 17 minutes ago, Ba Erv said: I’ve been confused about this for months. Sean Reid also mentioned in his testing that base ISO was around 160…which doesn’t exist on the camera. For me the battle with this camera has been preserving the highlights while monitoring the histogram. The highlight spike on the histogram seems to go from midrange to off with merely a 1/3 change of exposure compensation between ISO 100 vs 200. There doesn’t appear to be any smooth transition. Someone educate me, pleeeeese! Bill Claff has mentioned to me that the sensor might be saturating before clipping of the ADC at ISO 100. Determining the base ISO of the sensor under those conditions will depend on what deviation from linearity is allowed at the upper end of the photon transfer curve. If you allow a lot of nonlinearity, and Bill's conjecture is what's going on, then the base ISO is about 100*(16383/12521) = 131. Don't hold me to that calculation. It's late here. Edited May 20, 2022 by JimKasson Link to post Share on other sites More sharing options...
Ba Erv Posted May 20, 2022 Share #13 Posted May 20, 2022 25 minutes ago, JimKasson said: Bill Claff has mentioned to me that the sensor might be saturating before clipping of the ADC at ISO 100. Determining the base ISO of the sensor under those conditions will depend on what deviation from linearity is allowed at the upper end of the photon transfer curve. If you allow a lot of nonlinearity, and Bill's conjecture is what's going on, then the base ISO is about 100*(16383/12521) = 131. Don't hold me to that calculation. It's late here. Thanks, correspondIngly it’s early here so I need another Red Bull and a few more espressos before math. Link to post Share on other sites More sharing options...
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