#41  
Old 20-03-2010, 02:53 PM
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dhein (David)
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500D vs 500D Noise - batch variations DO exist

Hi all - here's a follow up to my previous email.

500D vs 500D.

I finally had a chance to compare 2 x 500D's last night, so at last an apples vs apples comparison. I think the results speak for themselves.

These were taken within an hour of each other, temp was around mid 20's, both camera's were switched on fresh and had not been running before. Lens was removed, and bayonet capped, view finder facing down against hard top to minimise light entry. Settings were ISO1600, 4 mins. Camera's internal dark frame routine disabled.

Below samples are 100% crop containing both JPG & RAW as camera's were set to dual output mode.

Regardless of stacking technique, it's pretty clear that from step 1, I'm already at a significant disadvantage as my sensor produces significantly more noise.

At least this now proves to me, that there are indeed batch variations between the same model camera. Maybe this isn't that common, but it obviously exisits. Maybe it's a fault in the chip, maybe a fault in the electronics or DGIC4 processing ..who knows.

But these are legitimate comparisons between two indentical cameras.

Now I need to check whether mine is still under warranty!

Cheers
David
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  #42  
Old 20-03-2010, 03:06 PM
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hotspur (Chris)
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re camera gear

Just wondering if others have heard or delt with 'Digital World International',that was mentioned by another member in this thread,
I went and had a look the prices seem almost to good to be true,compared with other grey importers,I may be buying a 17-55 f2.8
some time soon,and they had them listed for $1166,while others have them around $1475.would like to see if people have bought stuff of them,and what their recomendation is,Thank you

Oh,and to the original question,I have a 450D and it works very well for astro and terrestrial work,if i was to look at another body,i would certainly chevk out the new 550D,Really don;t know much about it,but it
seems some of the 7D trappings have rubbed off on it,The video cababilities would be interesting and with an L lens.........

cheers Chris
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  #43  
Old 20-03-2010, 05:04 PM
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Octane (Humayun)
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David,

One thing you might like to check on Fiona's camera, in the custom settings, is to see whether she has high ISO noise reduction enabled.

That setting makes an enormous difference. People sometimes confuse that setting with long exposure noise reduction. Two different things. In fact, you might want to check that she has long exposure noise reduction disabled, too.

I can't understand why there'd be such disparity between two same models.

H
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  #44  
Old 21-03-2010, 10:08 AM
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dhein (David)
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Hi Humayan,

Yes, I indeed checked those setting which were disabled. I've also played with all those combinations on my own camera. While they all make some difference, the only one (on my camera at least) that really makes a noticab le difference is the long exposure noise reduction. Infact the in camera routine does a decent job in removing a lot of that red & blue noise in my samples. However when you've got limited time to image your lights doubling each light exposure chews up valuable time while the object still remains in view. So of course I'd prefer to use darks and take them imediately after my lights are done.

While I found it hard to believe that there could be such variation between cameras, Fiona's results seem to back up the extensive reviews posted on Gary Honis's site that I referenced earlier - and the general consensus that the 500D does a decent job of dark frames.

I think I'm the odd one out here.

Cheers
David
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  #45  
Old 21-03-2010, 07:55 PM
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tlgerdes (Trevor)
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Dave,

I think it is time to go and talk to your camera shop and get it fixed or replaced. You have done extensive testing and have some interesting evidence to suggest you have dud.
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  #46  
Old 21-03-2010, 08:25 PM
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dhein (David)
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For anyone interested in reviewing the orginal JPG/RAW files from each camera and making your own judgements, I've posted them here - http://dhein.no-ip.org/public/DSS/500D%20vs%20500D/

In the meantime, I'll be looking to see if this can be replaced under warranty. Thanks for all the feedback & suggestions.

Cheers
David
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  #47  
Old 22-03-2010, 08:22 AM
ghonis
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500D Dark Frame Noise

Hi David,


Sorry for the delay in getting back to you. Looks like you have the situation resolved and the problem was receiving a 500D with a noise problem. When I modify Canon DSLRs, I take test dark frames before and after modifying each camera. One reason I do this is to check if the camera has a bad horizontal banding problem for long exposures before modifying the camera. Of all the 450D, 500D and 1000D cameras I have modified, none have had the banding problem, mostly reported by some owners of the 40D. The other reason is to be sure that during the modification, I have not done anything inside the camera that results in a noise problem.


The 500D cameras I have modified all have very low noise, like the 500D used for my (450/500D/1000D) noise comparison web page. I have found that the dark frames of each camera model can vary very slightly from camera to camera, but not to the degree that your comparison to Fiona's 500D is showing. Just to be sure that all settings are the same between each camera when you're doing a comparison is to use Canon's DPP to show "Info", "Shooting Information" and compare the settings of both cameras side-by-side. I've found that even the white balance setting can affect the RAW dark frames. A "Daylight" setting gives a lower noise RAW dark frame than "AWB" on some cameras for some reason.


As Humayun recommended, it is important to cover the viewfinder with the viewfinder cover (attached to the strap) when taking dark frames (and long exposure light frames).


Good thing you were able to do the side-by-side comparison to document the problem and hopefully, Canon will replace your camera under the warranty.


Anyone interested in DSLR modifications is invited to join the DSLRmodifications Yahoo group at:


http://tech.groups.yahoo.com/group/DSLRmodifications/


Gary Honis
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  #48  
Old 22-03-2010, 08:40 AM
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wasyoungonce (Brendan)
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Hi Gary

Good to hear you in this forum.
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  #49  
Old 22-03-2010, 11:38 PM
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dhein (David)
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Hi Gary,

Many thanks for the detailed reply. Having just reviewed some ISO400 tests @ 4 mins, which also contain tons of noise - I'm definately going down the replacement path if I can convince my supplier that Canon will accept this as a fault.

Cheers
David
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