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  #21  
Old 30-01-2008, 04:00 PM
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skwinty (Steve)
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Hi all
Herewith my reasoning. Assume a 14bit analog to digital converter .Max levels =16384.
Assume 1 electron = 1 analog digital unit .
Assume 10 electrons readout noise.
ISO=gain therefore amplify noise as well as signal.
ISO 800 = 4 X greater than ISO 200.
If exposure time decreases so does signal assuming constant source .
Read out noise is constant disregarding noise reduction. ie switched off. As can be seen the signal to noise ratio for raw stays the same between ISO 200 and 800 as well as for jpg(although worse for jpg).
Hence my statement no signal to noise ratio differential for raw but a large dynamic range difference.
Hence logic tells me better to use raw at low ISO and jpg at high ISO.
When shooting jpg it makes sense to use a high ISO because you need as much signal as possible considering the fact that the compression algorithm is going discard a large amount of data.
Dennis you were 100 % correct with respect to interval shooting from the EOS Utility software with MLU regardless of state of firmware version. The remote controller works fine with long exposures and MLU.
Perhaps a bug in EOS utility software?
Thanks for listening to my pedantic ramblings but this is how I learn.
Kind regards
Steve
RAWJPG(50%COMP)ISO200ISO800ISO200ISO800MAX LEVEL16384163841638416384SIGNAL10040050200LESS TIME LESS SIGNALREAD OUTNOISE10401040REMAINS CONSTANTMIN LEVEL0000DYN RANGE1638.4409.61638.4409.6S/N RATIO101055
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  #22  
Old 30-01-2008, 04:03 PM
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skwinty (Steve)
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Hi All
I see my nicely spaced tabled came out as garbage.
Please ignore
Regards
Steve
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  #23  
Old 30-01-2008, 04:44 PM
Dennis
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Quote:
Originally Posted by skwinty View Post
Hi all
Dennis you were 100 % correct with respect to interval shooting from the EOS Utility software with MLU regardless of state of firmware version. The remote controller works fine with long exposures and MLU.
Perhaps a bug in EOS utility software?
Thanks for listening to my pedantic ramblings but this is how I learn.
Kind regards
Steve
Hi Steve

On the contrary, having one’s posts peer reviewed is always a good thing, especially when writing about relatively new products and techniques where common knowledge is scarce.

I would hate to have written something about the 40D and EOS utility that was completely incorrect, perhaps causing a potential purchaser to either buy or not buy the camera, so it is always useful for others to post their experiences.

In fact, I benefit even more because I then have to re-examine my own work and notes and I always end up walking away much the wiser. Such is the richness of Forum life!

Cheers

Dennis
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  #24  
Old 30-01-2008, 04:47 PM
Dennis
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Quote:
Originally Posted by iceman View Post
Yes - that's exactly the problem my friend and I had on the night we used his 40D. We were trying to control it remotely, but couldn't because MLU was enabled.
We couldn't see the red triangle because of the red cellophane over the screen

Err…but Mike, the warning triangle is yellow (albeit with a red insert )…although the LED icon is indeed red.

Cheers

Dennis
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  #25  
Old 30-01-2008, 04:58 PM
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hi All
herewith a spreadsheet with the data in a readable format
Regards
Steve
Attached Files
File Type: doc ISO.doc (41.5 KB, 25 views)

Last edited by skwinty; 30-01-2008 at 05:08 PM.
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  #26  
Old 31-01-2008, 09:19 AM
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rogerg (Roger)
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Dennis,

Thanks for showing the examples - I have been wanting to see what it actually looks like, I doubt I will get a chance in real life for quite a while yet.

Roger.
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  #27  
Old 31-01-2008, 11:30 AM
Dennis
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Hi Roger

I should have mentioned that in the example of Rigel and its companion, I focused using the much fainter companion and not on the saturated (blobby) primary.

I use a Moonlite motorised focuser and I found that I could press the focus motor movement keys inside and outside of (perfect) focus for a reasonable length of time before the saturated Rigel image changed in size.

However, by concentrating of the faint companion, exact focus was so much easier to find and was precise, requiring only very minute button presses between spot on and slightly out of focus.

I think the default exposure setting of the image in “Remote Live View” is automatic although I do believe you can over ride this to set your own exposure and display the histogram. By default, the histogram is OFF in Remote Live View.

Also, the histogram (when enabled) only displays during the un-zoomed, full FOV frame in Remote Live View, not in the zoomed in window that is showing Rigel in the example above.

Cheers

Dennis
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  #28  
Old 31-01-2008, 03:18 PM
chunky (Clinton Wood)
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Hi there,

I have a newly self-modded 40D and have used the remote shooting. As long as live-view is activated, then you can go with the timer and still have MLU - since the chip is reading light data, then the mirror is already 'locked-up', so no need for MLU. But if live view is off, then the TC80N3 is the only way to do MLU shots.

Regarding ISO:
There is a school of thought that because of the 14-bit light collection (never, never use jpg that only gives 8-bits of data and with artefacts), the Canon reaches 'gain-unity' at ISO 400, so from a astrophotography point of view you never need to go above this. For a 20/30D I think the figures are around ISO 1000 (only possible on the 30D - 800 or 1600 on 20D etc).
For back-of-the-camera colourful shots, however, you need 1600 and 3200 to get the intensity to get good colour - great for star-parties.
Regarding Live View and Noise:
No problem from increased noise with LiveView - since we are always taking sequences anyway, and unless you deliberately keep 30sec between frames to cool the sensor, then don't worry.

If anyone wants their 40D modded, or wants an older 20D already modded, just let me know

Regards
Clinton
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  #29  
Old 31-01-2008, 03:58 PM
Dennis
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Hi Clinton

Thanks for the report on your experiences. I cannot find the source where I read about “Remote Live View” (RLV) and an increase in noise, so I am heartened to hear of your experience.

I had planned to shoot a series of tests (if the clouds ever clear) between 180 sec images taken with and without RLV active and compare the results.

Cheers

Dennis
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  #30  
Old 31-01-2008, 09:25 PM
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citivolus (Ric)
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Quote:
Originally Posted by chunky View Post
Regarding ISO:
There is a school of thought that because of the 14-bit light collection (never, never use jpg that only gives 8-bits of data and with artefacts), the Canon reaches 'gain-unity' at ISO 400, so from a astrophotography point of view you never need to go above this. For a 20/30D I think the figures are around ISO 1000 (only possible on the 30D - 800 or 1600 on 20D etc).
Thanks Clinton, you inspired me to do some reading, and after having a look at http://www.clarkvision.com/imagedeta...mance.summary/ I now understand what you are saying. My understanding is that this has the most impact if you are stacking images, as a single photon per frame will be visible in data shot at ISO 400, while taking it up to ISO 1600 would just give quantization error and gaps in the histogram, even if pulling the data slightly more above the read noise. By the time you have stacked 8 frames or so at ISO 400, read noise should average out and be subtractable, and single photons should be apparent, leaving you with just the signal and the thermal noise. You then have a larger well to work with and can shoot a longer exposure without saturating.

Amusingly as an extension of this, artefacts aside, unity gain for JPEG shooting would be somewhere around ISO 20,800

Regards,
Eric
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  #31  
Old 31-01-2008, 10:41 PM
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g__day (Matthew)
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Sigh - my brother tells me nothing! I suggested this functionality to him over a year ago - complete USB control and a preview over USB 2. Guess the research labs have to stay secretive - annoys me that I read it here first!

PS

Can the software control older cameras Canon 300D 350D 400D? Canon often do that but only bundle the latest software with their newer gear to further sweeten the pot!
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  #32  
Old 01-02-2008, 05:15 PM
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skwinty (Steve)
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Hi Eric
Thanks for posting the link to R.N.Clarks web site.
The article sure sheds some light on the complexities of DLSRS and astrophotography.
Regards
Steve
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  #33  
Old 02-02-2008, 09:13 AM
Dennis
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Quote:
Originally Posted by g__day View Post
Can the software control older cameras Canon 300D 350D 400D? Canon often do that but only bundle the latest software with their newer gear to further sweeten the pot!
Hi Matthew

On my CDROM there were 2 versions of the EOS Utility Software for camera control and Remote Live View shooting.
  • One for the EOS-1D Mark III and 40D family and,
  • One for the 300D, 350D, 400D, 20D, 30D, etc. family.
This may indicate that these are two functionally different families of cameras and therefore you may not be able to mix and match the SW utilities?

Cheers

Dennis
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