First Canon EOS 60Da samples (Andromeda, Orion & Pleiades)!

[M.A.S. Productions]

To me, the image from the 60D looks better. The image from the 60Da just looks more red.

[Heidrun]

Hope that there wil come some pictures of the milky way with a wideangle lens and 60DA. Because if im gonna get this type of camera. I would 999 times out of 1000 use it to get pictures of the milky way or maybe Aurora Boralis

[kdsand]

 

Just a thought ( ouch )

These pictures were actually taken with a Nikon........
 


No my bad its the other way around.
That is me being sarcastic

[whwang]

[I'm very surprised to read this, but it sounds great! Do you have numbers for what the dark current actually is for modern DSLR sensors, e.g. in terms of electrons/hour?

My own measurement on 5D2 is 0.86 electron per second at 20 deg C, and 0.051 electron per sec at 3 deg C. These are ambient temperature, not sensor temperature. The sensor must be much hotter after continuous operation of several 10s of minutes. The full report I wrote is here:
http://www3.asiaa.sinica.edu.tw/~whwang/misc/Canon5D2.pdf
It is oriented for astronomers.

In general, this page of Roger Clark's is an excellent source for sensor performance that amateur astronomers care:
http://www.clarkvision.com/articles/digital.sensor.performance.summary
Unfortunately Roger's page does not contain much information on the dark rates.

[lol]

I wonder how much better the 60Da is over a stock 60D, or if this just marketing talk to market to the astronomer niche market?

See following link for an indication of the possible difference, as they show the sensitivities of a 40D before and after modification. Note the increased red sensitivity, particularly around 6563 angstroms, which is where most of the "red glowy stuff" from nebulas sits. Assuming they haven't radically changed their colour filter since the 40D, then a similar gain is possible. Also note it doesn't significantly change the green or blue sensitivities.
http://www.astrosurf.com/buil/50d/test.htm

Hope that there wil come some pictures of the milky way with a wideangle lens and 60DA. Because if im gonna get this type of camera. I would 999 times out of 1000 use it to get pictures of the milky way or maybe Aurora Boralis

The IR filter modification only gets you a benefit in the deep reds. So for broader spectrum objects like galaxies (including the milky way) there isn't much benefit over a standard camera. I'm not familiar with the causes of the Aurora glow, so I'm not sure if the Da would or would not help there. If it did, it would only be from increased red sensitivity.

Note both the above assume Canon only changed the colour filter, and didn't make any other changes which may improve the image output.

[epsiloneri]

My own measurement on 5D2 is 0.86 electron per second at 20 deg C, and 0.051 electron per sec at 3 deg C.

Thank you for doing this, very useful and interesting reading. Did you also characterise the variation of the flat field and the static dark current image? I.e., how much noise you would introduce by not correcting for flat field and dark. I've been impressed by how flat the dslr sensor appear compared to CCDs, so I've wondered if Canon actually has some first-order built-in flat fielder.

[whwang]

Thank you for doing this, very useful and interesting reading. Did you also characterise the variation of the flat field and the static dark current image? I.e., how much noise you would introduce by not correcting for flat field and dark. I've been impressed by how flat the dslr sensor appear compared to CCDs, so I've wondered if Canon actually has some first-order built-in flat fielder.

For pixel response, modern sensors in the visible light are all very flat to begin with. This is true for both CCD and CMOS. I think, the most important flat field effect is introduced by the optics (vignetting) rather than by the sensors. Personally whenever I do astrophoto, I try to get a good flat field image to correct for the vignetting (and dust shadow).

For the dark part, as I mentioned in the PDF file, it is not possible (at least to my knowledge) to measure the real dark current in Canon CMOS. I can only measure the frame-to-frame variation of dark images, which is dark noise, and use that to infer what the dark current may be. The frame-to-frame variation is very small as long as temperature is stable. This means that a proper dark subtraction can remove thermal effect very cleanly and leaves very little trace of noise in a dark subtracted image.

[epsiloneri]

For the vignetting, I assume you would only have to take a "master flat" for the lens/camera combination once and for all, and then keep re-use it (much like is done in DPP and DxO). Dust may move around of course. I was more interested in the pixel-to-pixel variation of the flat field - how flat is very flat? If you haven't measured it - no problem I can do it myself when opportunity presents, I was just curious if you already had the data. Same thing for the dark current static structure - how much is the pixel-to-pixel variation? I understand it's a differential measurement, but one should anyway be able to measure this (otherwise one couldn't calibrate for it).

0.05 electrons/pix/sec is great performance, 1 electron/pix/sec not so much. The dark current seems to be (surprisingly) temperature sensitive in this regime. That means one needs to match the temperature of the sensor fairly accurately for the dark. Alternatively, optimise the dark subtraction by scaling it with the help of a bias frame.

The 5D2 sensor is also famous for some "band" structure in the dark that unfortunately is not stable in between exposures, and so very difficult to properly remove. Have you made any progress in this area? It will be interesting to see if the 60Da improves in this area.