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Old 04-07-2016, 03:47 PM
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luka
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Cooled Canon 450D settings

Got the cooled 450D going and have few questions:
1. Is it possible to switch off the back display? When imaging from a PC it is showing a timer and when not imaging it is showing the usual info. I looked through the options but could not fix this. A piece of black tape over the sensor just above the screen works but I thought there may be a more elegant solution.
2. APT (astrophotography tool) and 450D... Live view works and shows stars but if I try to zoom in the stars are gone and I only get the noisy background. What is going on? The 1200D works fine with the same options.
3. Mirror lock up does not work with APT. Any hints?

And finally, triggered by the Glen's comment in my post here, what is the best ISO for a cooled 450D?
ISO800 was suggested as the optimum but this may change when the sensor is cooled to zero as the noise will be reduced. What ISO do the others who did the cold mod use?

Thank you in advance
Luka
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Old 04-07-2016, 04:41 PM
glend (Glen)
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Luka you can turn off the Liveview screen display, use the Disp button after you have framed and focused. Leaving the countdown timer on the display can lead to light leaks on long subs. Re ISO i was shooting narrowband at ISO1600 with the mono camera, which needed max sensitivity with the sensor cooled to max. Remember that the 450D sensor achieves optimal noise reduction once you get to 0C, there is not much to gain by pushing it down to -10C or lower. Rowland did some dark comparisons at various temperatures to come up with 0C target.
Craig Stark did some tests on various Canons and suggested ISO800 was the sweet spot in terms of SNR.
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Old 04-07-2016, 10:24 PM
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Glen, thank you for your reply. Especially thank you for the pointer to the articles by Craig Stark. It was really great reading the detailed analysis.

To summarise the main points (for 450D, 50D and 5D-II):
  • ISO400 gives the best dynamic range and values lower than 400 should not be used (unity gain).
  • "... ISO 800 or 1600 represent the sweet spot with ISO 800 perhaps being the more balanced of the two."
  • "Running higher than ISO 1600 will end up not gaining you any signal to noise and will only serve to severely limit the dynamic range of the image."

While a cooled DSLR is never mentioned, I think that the cooling would not change the dynamic range or the read noise. So the same conclusions apply.
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