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Author Topic: Real iso's?  (Read 8461 times)

privatebydesign

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Re: Real iso's?
« Reply #15 on: May 28, 2013, 12:13:05 PM »
Can I get some credit here??  In the post that the OP is speaking of, I DID tell dilbert he was wrong!  :)

We give you credit  :)

Now go and fix that 400 mount  :(
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Re: Real iso's?
« Reply #15 on: May 28, 2013, 12:13:05 PM »

MxM

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Re: Real iso's?
« Reply #16 on: May 28, 2013, 12:42:29 PM »
I did an ISO test with my 7D.

Put the camera in a dark room (basement) leave the lenscap on, close/block the viewfinder, use RAW or disable ISO long exposure/noise reduction. Choose the settings that you want (Manual mode). Take every picture for at least 10 seconds and you will come up with al list like me.



The 7D is an 18MP camera which is equal to approx. 18MB file size. (the smaller the file size, the cleaner the image is)

As you can see is ISO 160, 320, 640 the camera's sweet-spot... The golden rule is that the limit is MP/MB+1(file size) so 19MB is in the safe/clean zone and 20MB is pushing your camera. It's no math, just hard numbers.

MxM
« Last Edit: May 28, 2013, 12:48:24 PM by MxM »

Rocky

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Re: Real iso's?
« Reply #17 on: May 28, 2013, 01:11:18 PM »
Based on Bill Claff's data, The canon 30D has quite low readind noise. Any camera after that the read noise has been at least doubled up, includind the 1D-X.  Why???  Is Canon is going backward on the read noise???

privatebydesign

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Re: Real iso's?
« Reply #18 on: May 28, 2013, 01:37:00 PM »
Based on Bill Claff's data, The canon 30D has quite low readind noise. Any camera after that the read noise has been at least doubled up, includind the 1D-X.  Why???  Is Canon is going backward on the read noise???

It is because you are comparing 12 bit to 14 bit files.
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Sporgon

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Re: Real iso's?
« Reply #19 on: May 28, 2013, 01:48:35 PM »
Based on Bill Claff's data, The canon 30D has quite low readind noise. Any camera after that the read noise has been at least doubled up, includind the 1D-X.  Why???  Is Canon is going backward on the read noise???

It is because you are comparing 12 bit to 14 bit files.


At Building Panoramics we shoot a lot of skys for our library and of all the Canon cameras we've used the 30D was by far the worst for noise, in fact worse than the 20D for some unknown reason.

With regard to Neuro's link, this confirms what I have found in practice. I could never see this '160 ISO is less noisy than 100' statement that's bandied about, but I do find 50 gives noiseless data due to it's 'overexposure pulled back' value.

Actually it was Privatebydesign's link. I can't find the practical link with Claff's data. So the 5D mk2 has the same read noise at ISO 640 as it does at 100 ? Yet shoot a sky at ISO 640a and it's full of noise whereas 100 is ( reasonably) clean. Likewise ISO 125 is similar to 100.

If you're exposing in total darkness with the lens cap on surely you are under exposing never mind how long you leave the shutter open. What about heat generated at these long 'exposures-that-aren't' ?

?
« Last Edit: May 28, 2013, 04:07:04 PM by Sporgon »

bdunbar79

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Re: Real iso's?
« Reply #20 on: May 28, 2013, 02:22:01 PM »
Can I get some credit here??  In the post that the OP is speaking of, I DID tell dilbert he was wrong!  :)

We give you credit  :)

Now go and fix that 400 mount  :(

 :'(
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dppaskewitz

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Re: Real iso's?
« Reply #21 on: May 28, 2013, 02:45:49 PM »
Has anyone done any testing of the 6D?  According to Claff's charts, the 5DII, 5DIII (and 30D, for that matter) seem to follow one pattern (less noise at 160, 320, etc.) while the 5D classic (my other body) follows a 100, 200, 400 pattern). 
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Re: Real iso's?
« Reply #21 on: May 28, 2013, 02:45:49 PM »

Click

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Re: Real iso's?
« Reply #22 on: May 28, 2013, 02:52:27 PM »
Very interesting thread. I'm following this closely. Thanks for the great info.  8)

RGF

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Re: Real iso's?
« Reply #23 on: May 28, 2013, 04:11:56 PM »
IThe golden rule is that the limit is MP/MB+1(file size) so 19MB is in the safe/clean zone and 20MB is pushing your camera. It's no math, just hard numbers.

MxM

Can you explain the golden rule?  Why is it true?  What does it measure?

RGF

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Re: Real iso's?
« Reply #24 on: May 28, 2013, 04:12:51 PM »
Very interesting thread. I'm following this closely. Thanks for the great info.  8)

+100

Pi

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Re: Real iso's?
« Reply #25 on: May 28, 2013, 04:30:39 PM »
As you can see is ISO 160, 320, 640 the camera's sweet-spot...

When you shoot with the cap on...

Sporgon

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Re: Real iso's?
« Reply #26 on: May 28, 2013, 04:35:54 PM »
I did an ISO test with my 7D.

Put the camera in a dark room (basement) leave the lenscap on, close/block the viewfinder, use RAW or disable ISO long exposure/noise reduction. Choose the settings that you want (Manual mode). Take every picture for at least 10 seconds and you will come up with al list like me.



The 7D is an 18MP camera which is equal to approx. 18MB file size. (the smaller the file size, the cleaner the image is)

As you can see is ISO 160, 320, 640 the camera's sweet-spot... The golden rule is that the limit is MP/MB+1(file size) so 19MB is in the safe/clean zone and 20MB is pushing your camera. It's no math, just hard numbers.

MxM


But what practical data is established by exposing the sensor in the dark for ten seconds ? Surely you are chronically under exposing never mind how long you leave the shutter open. The sensor will start to generate heat.

I see your data matches the Bill Claff charts for the 7D. Looking at the 5D mk2 data it stated that the read noise is the same at ISO 640 as it is at 100. This will give people the impression that your data will show the same amount of noise at these exposures, but this just isn't the case. Shoot a sky at ISO 640 and it is very noisy. Shoot at ISO 100 and it's pretty clean: there is no comparison in data quality - so what's all this read noise meant to mean in practice ?

I think it is very misleading - unless of course you like to shoot inside of lens caps in the dark.

privatebydesign

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Re: Real iso's?
« Reply #27 on: May 28, 2013, 05:07:34 PM »
Pi and Sporgon, you are missing the point.

The point is that the read noise displayed is added to a regular shot in lesser amounts at shorter exposures. You can argue the relevance, but when you are trying to pull that last bit of detail from a dark shadow that tiny extra amount of noise might make the difference.

It is all about setting yourself up to get the last 1 or 2 % of your sensors capabilities, this small difference is best illustrated with long dark exposures, but is just as valid for shorter brighter ones.
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Re: Real iso's?
« Reply #27 on: May 28, 2013, 05:07:34 PM »

Pi

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Re: Real iso's?
« Reply #28 on: May 28, 2013, 05:22:25 PM »
Pi and Sporgon, you are missing the point.

No, you are just misreading my posts.

Sporgon

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Re: Real iso's?
« Reply #29 on: May 28, 2013, 06:11:24 PM »
Pi and Sporgon, you are missing the point.

The point is that the read noise displayed is added to a regular shot in lesser amounts at shorter exposures. You can argue the relevance, but when you are trying to pull that last bit of detail from a dark shadow that tiny extra amount of noise might make the difference.

It is all about setting yourself up to get the last 1 or 2 % of your sensors capabilities, this small difference is best illustrated with long dark exposures, but is just as valid for shorter brighter ones.

Well I'm going to have a look at this tomorrow. By the nature of what I shoot I'm nearly always on ISO 100, so don't have many files I can use as a comparison, but at the moment I believe that ISO 100 is much better than 640 in every way, quality and post process -wise.

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Re: Real iso's?
« Reply #29 on: May 28, 2013, 06:11:24 PM »