Canon 6D best for astrophotography?

[gregbradley]

An interesting comparison of Canon 5D2, 5D3 and new 6D noise in darks.

http://www.petapixel.com/2012/12/13/canon-6d-and-5dmk3-noise-comparison-for-high-iso-long-exposures/#eezbZG7PFOQCb6EJ.99

6D is clearly ahead of both 5Ds. It looks like Canon have improved noise levels again with the new camera.

Greg.

[Octane]

Go, team!

Might make a decent nightscape camera.

H

[2stroke]

Digi 5+ FTW, lol just waiting now for the next entry level to replace the 1100D with to come out. Please give poverty stricken people like me a 1200D with digi 5+ canon for 2013 hahaha

[Shiraz]

Looks impressive, but it might be problematic to rely on darks to assess DSLRs - apparently Canon does a lot of background processing that makes darks look better than they really are (in a simplistic 1 on 1 comparo), so the apparent performance improvement of the new cam may have much to do with upgraded cosmetic processing.
http://www.stark-labs.com/craig/resources/Articles-&-Reviews/CanonLinearity.pdf

[Octane]

Ray,

The background processing as far as I know is applied in the JPG engine.

From what I know, Canon RAWs aren't cooked.

H

[Shiraz]

hi Humayun

The point of the referenced article was that Craig Stark found the processing was applied prior to the CR2 - which is not what I thought RAW was about. However, his results speak for themselves - clear evidence that Canon do mess with data that goes into the RAWs. And why not if it makes your camera rate highly in typical "it looks better" type evaluations?

Regards Ray.

[2stroke]

DIGIC 5+

Digic 5+ is an enhancement to the Digic 5 and Digic 4. The performance is said to be 17x the performance of the Digic 4. [10] (http://en.wikipedia.org/wiki/DIGIC#cite_note-10) The additional processing power allows for higher frame rate in continuous shooting (burst) modes, and greater noise correction through the use of signal processing.
Digic 5+ is used in the Canon EOS-1D X (http://en.wikipedia.org/wiki/Canon_EOS-1D_X), Canon EOS 6D (http://en.wikipedia.org/wiki/Canon_EOS_6D), and the Canon EOS 5D Mark III (http://en.wikipedia.org/wiki/Canon_EOS_5D_Mark_III).[11] (http://en.wikipedia.org/wiki/DIGIC#cite_note-11) The EOS-1D X includes dual Digic 5+ processors, allowing for a capture rate of 12 frames per second in RAW + JPEG, and an additional DIGIC-4 processor specifically for its Intelligent Subject Analysis System.[12] (http://en.wikipedia.org/wiki/DIGIC#cite_note-12)


I would not call that cheating, just smart time to find some real facts i guess. Also what are other camera manufacturers doing? Also this camera is a massive leap over others canons even those with the digi 5+ :)

[Shiraz]

I'm not knocking Canon at all - I own a couple and the 6D is undoubtedly a fine camera.

I am just saying that you cannot really be sure how low the noise of any DSLR chip is by just looking at some stretched RAW darks - the data may well have already been processed in a variety of ways that make it look better. The Stark paper suggests that both gain and offset modification are employed in the 450D - who knows what they do in the 6D or any other modern DSLR? After all, the new processors can implement a wide range of operators and would seem to have enough power to run almost any of the standard noise reducing algorithms.

It is probably more meaningful to compare dark variance and hope that no adaptive smoothing has been applied in low signal regions. Or maybe just take some side-by-side astro images with identical pixel scales and compare the results.

[midnight]

Hi all,

Thought I might add some 6D images I took last night.

Returned home for 1 day and lucky for me last night I could stay up without work committments. In fact I had to get my mount out of storage so it was good to get it out.

6D first real run on a tracking mount (G11).

Image 1 - Orion Nebula Crop
6D + EF200mmF2.8L @ F4
ISO 800
180sec
Unguided with a G11
Straight from RAW - no processing at all.
JPG quality = 7

Image 2 - Eta
6D + EF200mmF2.8L @ F4
ISO 3200
60sec
Unguided with a G11
Straight from RAW - no processing at all.
Jpg quality = 6

Image 3 - 180sec ISO800 Dark
Stretched in Canon DPP with a single point curve at 128,187.
JPG quality of 9

If you would like a copy of the RAW or export to TIFF, please PM me as I am not the best to judge these things. I will be heading intertstate again tomorrow for work so won't be home until next weekend.

I would be very interested to hear your thoughts on this camera & will read this thread with interest.

Cheers,
Darrin...

[Logieberra]

Yay, we grabbed our 6D from HarveyN last Friday. Thanks for the post Greg, looks like we did ok :)

[Logieberra]

A few quick guided test shots.
Single exposures.
JPEGs.
No Canon noise reduction and no darks.
Photoshop RGB levels used to fix the major red bias from street lights, along with edges cropped off (I really need a field flattener).

Galaxy_ISO_400_13mins
Horse_ISO_400_15mins
M42_ISO_400_10mins(HeavyClipped)
M42_ISO_400_20mins(Unclipped)

[Logieberra]

Oh, and I had the 6D's Wifi on the whole time which MAY heat things up a little - as it sure does a number on the batter life (I controll the 6D wirelessly via EOS Remote, no USB cable, it's a beautiful thing - Wifi is definitely not a gimmick here).

[g__day]

Craig Stark did an indepth analysis of what Canon cameras are doing with their shots before creating the RAW files, after processing 11GB of darks and flats with them!

http://www.cloudynights.com/item.php?item_id=2786

Conclusions

So where does this leave us? There are several take-home messages from these results:


Canon is re-scaling your data before it hits the CR2 file. Based on the thermal signal (likely based on stats from the optical black portion), it is both shifting your histogram left (i.e., subtracting a constant from the whole image) and scaling the intensity (changing the contrast or gain).
This makes the camera appear to have very low dark current as the background never gets appreciably brighter. But, the noise increase shows that the dark current is there and it is really the noise from the dark current that’s the trouble – far more than the constant component of the increase.
The camera warms up for a substantial period of time.
The above makes dark subtraction a real challenge. Not only is the current changing with time as the camera warms up (which we might easily account for), but what scaling is being applied to the data is changing as well.
Software designed for daytime photography will also rework the data and making it stay purely linear and not apply any processing can be difficult.
The camera’s internal gain (e-/ADU) for each ISO value points toward limiting the ISO to 400 and not using higher values. Both in theory and in practice, using higher values limits the dynamic range and does not let you pull out fainter details from the noise (even if they look brighter). The exact optimal ISO value will likely vary from model to model, but it's unlikely to be the high ISO settings.

We might ask ourselves at this point why the data get rescaled in the first place. Canon, after all, is filled with bright engineers, the cameras are very successful, they take great images, and this practice has been going on in their cameras for some time (at least since the old DIGIC II 350XT). The answer, in my opinion, is that the scaling makes perfect sense. They are compensating for inherent constraints placed on them by the sensor (which in turn gets to blame physics – good luck winning that debate!). Today’s DSLRs will do in-camera compensation for all sorts of things, now including lens distortion and chromatic aberration. These corrections get into the raw data and are far more complex than dark current.
The overwhelming majority of users would want the camera to avoid shifting the histogram far to the right as the exposure lengthens. Keep things under control as best as you can to make an image! Surely that’s better than having the image get lost by being washed out. Likewise, since many people shoot in 8-bit JPEG, ISO ratings well above what might be optimal for dynamic range are a good thing as they boost the signal into the range of intensity values that work well for the 8-bit, gamma-stretched JPEGs. It lets you get an image and see it there on the screen without going back and using image processing software to stretch the raw data. So what if a bit of dynamic range has been lost – you have an image!
These are perfect engineering arguments (as is the one to have an IR blocking filter cut off the H-alpha line). The Canon DSLRs do very well in astrophotography. But, they’re not designed from the ground up for this. They’re designed for a different market and their engineers make different choices as a result. Some of the choices impact how well the camera works for astrophotography.
Hopefully, we now know a good bit more of what we’re up against. I, now, at least have some information that will let me determine better means of doing dark-correction in software. For the times when I will grab my DSLR for astro work, I also know more about the ISO setting and how to optimize it for my images. Every tool has constraints on how best to use it. This helps us understand a bit more about those built into the Canon DSLRs.

[midnight]

Very interesting read! Thanks for this information;). I am finding my 6D is taking the shackles off my lense with that extra real estate. This is great for what I do at work which requires detailed photos to be taken in factories for wiring and often in very low light where a flash is not recommended or allowed.

Comparing the 6D to the modified 40D for astro work is my main aim when I finally get my chance to set back up again. There is a large generational gap between the two cameras with each having it's benefits.

Cheers,
Darrin...

[Lester]

Thanks for the link Greg, very interesting. I had been thinking of the 5D MK III when the funds allow, and will put that on hold now as the 6D looks very impressive. All the best.

[skysurfer]

I think the 6D is a great camera. I have a 7d now and a while I considered upgrading, *but* the Sigma 10-20 and Canon 15-85mm get useless which I should trade for Sigma 12-24 and Canon 24-105L, which cost me another $1000, depends on how much I get for the EF-S ones. And the Astronomik CLS filter gets useless as well ...
And the telephoto range of my 70-300L shrinks to a mere 187mm APS-C equivalent. And no popup flash which is also a shame....

[iceman]

Seriously looking at a 6D now!

[Lothar]

Hello and thanks for the 6D photos. Were you able to have the camera's image displayed on the phone? Could you magnify it to aid with focussing ?
Does this feature eliminate the need to have a fold out screen?
Regards,
Lothar.

[Logieberra]

No need for fold out screen if using a laptop to image with. Image captured (wifi or usb) moves the RAW direct to laptop and displayed via Canon's digital photo professional.

In my earlier post I mention EOS Remote. Mistake. I meant EOS Utility. It's a superb little program for astro capture. 200x live view for focusing. Timer for single exposures or interval shooting.

The phone app is not so full featured. It can capture, but no timer. Some basic settings are available, exposure and ISO etc. You can see the photo once captured. Not sure if zoom is available.

[lazjen]

I started out using the EOS Utility, but BackyardEOS/APT kill it for AP features.

[Lothar]

Has anyone used a Full Frame DSLR (e.g. Canon 6D) on a Meade or Celestron 8" SCT? I wonder if there is any significant vignetting or out-of-focus-edge problem. Does anyone have any relevant photos?
Regards.

[Logieberra]

Lothar, the standard SCT has a small imaging circle. Google the specs for your model. Likewise, confirm the specs with a reducer in place. I'm certain it won't even come close to filling a full frame chip like the 6D. That real estate would be wasted. Major vignetting.

[Logieberra]

The 6D sensor size is 35.8mm × 23.9mm.

[Logieberra]

Hyperstar on Celestrons might be a match?