Dark Calibration Frames for Astrophotography with Olympus OMD Cameras

In this video I explain some of the science behind what dark frames are and how they eliminate noise. Some good file handling and file management is demonstrated as well. You will be very surprised at how much noise can be eliminated by applying darks. There will be two more videos. The next one will be on bias frames.

[@sabyasachibanerjee124]

This is the first time I understood in some real detail what Dark Frames are and why they are required and useful. Very nicely explained

[@TheNarrowbandChannel]

Great to hear!

[@wernerboe1420]

Just for your info - the Olympus E-M1X does records the current temperature at the moment the picture was taken and puts it into the EXIF.
I think the EM1-X it''s the only Camera on the market, your E-M1, EM1.2 or EM1.3. or any other Olympus MFT I'm afraid, these do not offer this.

[@TheNarrowbandChannel]

Hi Werner. You know yesterday I actually found that too. I was digging through the Em1x manual. Its on page 578 and 563 I think. The Em1 and Em1.2 you can only see it through exif data yes, but I have not been able to find an easy way to look at it on the Mac without using the terminal. Now the Em1.3 I would think should surely have this. It has been labeled the mini Em1x

[@matteoc2040]

​@@TheNarrowbandChannel I searched in the orf files of my em1.3 and found nothing about temperature. I think it's just an em1x and maybe tg-6 feature

[@TheNarrowbandChannel]

@@matteoc2040 I just did a search through the manual for the 1.3 and there seams to be no we to see it except of exif data.

[@johndolson8342]

@@TheNarrowbandChannel The Sensor Temperature data is recorded in the EXIF Data. It's just not displayed in most SW. Use Kuso EXIF Viewer. Scroll down alphabetically and you'll find "Sensor Temperature". It will show data something like this... 8 8 0 for 8 deg C, or 15 15 0 for 15 deg C. I know it works on both my EM5mk2 and EM1mk3. I suspect it's there for all models. We just have to work for it :-)

[@kamilrakowski23]

Rawdigger will show you exif with temp on m1mii and m1miii for sure.

[@jeffslade1892]

The MFT I have, the E-M5ii, G7, E-PL7 and GH4 all have intervalometers of up to 2 minutes (120s) exposure, and they will do dark frame subtraction in-camera, which you can turn off. However the internal long exposure NR (dark frame) understands the camera and can do better than the typical astro software app. The sensor on an Olympus will get a lot hotter than a Panasonic because it lacks the heat sink (for video). However Olympus provide the Capture app but Panasonic only provide a tether app for the GH5. The Panasonic backs will AF-lock accurately on stars (Startlight AF), on the GH4 this is undocumented but has locked on Jupiter; on the G7 (& later) it's an automatic function in low light, you get a small red square around the focus point rather than the usual green rectangle. The newest Olympus has 'Starry Night AF'. Both breeds need to be fiddled with to set up for nighttime photography; WB, contrast, sharpness and of course NR (there can be two or even three flavours of NR on board). I do wish the two companies would get their act together though, they're supposed to be compatible but their systems are diverging.

[@matteoc2040]

Thank you! very interesting. So we don't need to take dark frames immediately after the light frames, do we? I noticed that you didn't use any lens to take dark frames. So I can use them for light frames taken with any lens. The only important thing is to have the same temperature and the same ISO. Is it correct?

[@GrimstodDesh]

And exposure time. As long as those three things are the same u can take them at any time.

[@TheNarrowbandChannel]

As long as it's the same temperature, time and iso that is all that matters. And preferably the same year. Camera sensors age so data a year later may not match.

[@matteoc2040]

​@@TheNarrowbandChannel If you take, let see 100 photos, is the sensor temperature the same for all of them? Is it enough to evaluate just at the beginning? (or at the end?)

[@TheNarrowbandChannel]

@@matteoc2040 I evaluate about three times. When the camera is turned on and starts to take one photo after another you would be surprised at how much the sensor warms up. I know on nights where the temperatures were in the single digits F I have never seen my cameras temperature dip below 39f.