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FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
Thread started 18 Aug 2011 (Thursday) 19:04
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Idiot ISO and Numpty ISO

 
Canon ­ Bob
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Aug 19, 2011 17:15 |  #31

Daniel Browning wrote in post #12959724 (external link)
Also, any time a lens reporting to be faster than f/2.8 is used, Canon applies a hidden Idiot ISO. This is Canon's way of falsifying (er, "compensating for") the sensor's poor angle of response.

Are you certain that the "compensation" (falsifying) occurs with the reported maximum aperture rather than the selected aperture?

TIA
Bob


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TeamSpeed
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Aug 19, 2011 17:16 |  #32

WaltA wrote in post #12964809 (external link)
I think some would argue that point. The guys hacking the firmware on the 400D confirm that "some ISO settings are just software".

In implementing the Auto-ISO for the 400D they've only had it use native ISO for that reason.

I'm just saying .....

Given the contributions of uopt vs daniel over this topic, I know which I trust. ;-)a


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evilr00t
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Aug 19, 2011 17:21 |  #33

Canon Bob wrote in post #12964830 (external link)
Are you certain that the "compensation" (falsifying) occurs with the reported maximum aperture rather than the selected aperture?

TIA
Bob

You can find out if you have a lens faster than f/2.8 (preferably f/1.6 or faster). Take a picture wide open in manual mode, then take it again with the lens half unscrewed.


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WaltA
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Aug 19, 2011 17:46 |  #34

TeamSpeed wrote in post #12964832 (external link)
Given the contributions of uopt vs daniel over this topic, I know which I trust. ;-)a

Agreed. The interesting thing is Daniel has almost the same number of posts as uopt ....

Over my years on this forum when Daniel posts its usually well thought out and backed up with facts and references.


Walt
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S.Horton
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Aug 19, 2011 17:53 |  #35

uOpt wrote in post #12963435 (external link)
There's nothing to understand. It's all pulled out of thin air. It might be a cute metal model for people who prefer to think in mechanical and/or film photography terms but it has no meaning in the age of electronics.

It's very easy to disprove the "some iso settings are just software" theory by simply looking at the signal/noise ratio at the various iso settings.

And again, clipping is clipping. Stop overexposing. No clipping. Simple. You bump up iso, you reduce exposure time. Pretty basic concept, no?

You should check out the OP's credentials, then see if thin air applies.

Call me old school, but experts still have great value to me. Even if I have to work to understand their points.


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uOpt
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Aug 19, 2011 17:56 |  #36

A couple links to actual facts would be very useful then.

The XTi firmware team must have an email archive somewhere that contains a message explaining how they came to the conclusion you state above?

And even if it is all true, expanding the range by math only when going from 100 to 160 iso (as if done by a PP program) can lead to a quality increase if it is done on the floating point number before the quantization into a 14 bit integer. The clipping fear is still invalid since of course you were lowering your exposure time when upping your iso value, after all that's the point when going from 100 to 160 iso or whatever (I also don't see why this would ever clip on the lower end, aka shadows like the original post says).

I am not so much opposed to the concepts presented but to the lack of evidence. And some of the advise is wrong even if the facts were true.


My imagine composition sucks. I need a heavier lens.

  
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WaltA
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Aug 19, 2011 18:00 |  #37

uOpt wrote in post #12964993 (external link)
The XTi firmware team must have an email archive somewhere that contains a message explaining how they came to the conclusion you state above?

Happy reading.

http://chdk.setepontos​.com/index.php?topic=3​290.15 (external link)

Also in the wiki

http://code.google.com​/p/400plus/wiki/UserGu​ide (external link)

way down at the bottom about Auto-ISO

It doesn't really explain how they came to that conclusion but you can just ask them yourself on the wiki site.


Walt
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uOpt
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Aug 19, 2011 18:07 |  #38

WaltA wrote in post #12965009 (external link)
Happy reading.

http://chdk.setepontos​.com/index.php?topic=3​290.15 (external link)

Also in the wiki

http://code.google.com​/p/400plus/wiki/UserGu​ide (external link)

way down at the bottom about Auto-ISO

It doesn't really explain how they came to that conclusion but you can just ask them yourself on the wiki site.

Yeah. I appreciate the links but as you say, there is no indication why they came to the conclusion that some iso values are software only. At the level where they hack the cameras they wouldn't necessarily have stumbled across Canon's code to actually do it.

In any case, I'll be away doing the actual shooting thing for a couple days. I'll be sure to put in some iso tests! :)


My imagine composition sucks. I need a heavier lens.

  
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WaltA
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Aug 19, 2011 18:09 |  #39

Well, I'm sure you didn't read all the posts in that thread in the 7 minutes between my post and yours. You have access to the wiki where the developers are all gathered. Why don't you just ask them?


Walt
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yuribox
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Aug 19, 2011 21:33 |  #40

Interesting subject.
I will have to try this out.


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Sp1207
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Aug 19, 2011 21:44 |  #41

This is completely false. All my ISOs are real ISOs. Except +1600. Those are pushed.

I can do 'smart' ISOs (lol at your names) in post. Also, we have names for these already -- pushed, pulled, and native ISOs. In fact we were talking about this with this terminology in the CCD labs of the 1990s.

Not 100% not serious.


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NinetyEight
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Aug 20, 2011 03:32 |  #42

My head hurts! I must be a numpty or an idiot :-)
I just use the ISO that I need for the shot, although I do tend to avoid the 'in-between' (1/3rd stop) ISO's above 800.


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tzalman
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Aug 20, 2011 04:25 |  #43

Sp1207 wrote in post #12965923 (external link)
This is completely false. All my ISOs are real ISOs. Except +1600. Those are pushed.

That is because you have a IDs2.

In fact we were talking about this with this terminology in the CCD labs of the 1990s.

And in the darkrooms of the 1950s. In fact one of the foundations of the Zone System is pushing and pulling.


Elie / אלי

  
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Canon ­ Bob
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Aug 20, 2011 09:41 as a reply to  @ Canon Bob's post |  #44

evilr00t wrote in post #12964850 (external link)
You can find out if you have a lens faster than f/2.8 (preferably f/1.6 or faster). Take a picture wide open in manual mode, then take it again with the lens half unscrewed.

Ah yes, thanks.....the simple approach was a little too obvious for me :o

Bob


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cacawcacaw
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Aug 20, 2011 12:41 |  #45

Breaking it down into practical rules for simple minds (like mine):

  • Use full stop ISO's
  • Only raise the ISO when the exposure can't be further increased by shutter speed or aperture settings.
  • In low light, better to raise the ISO than to increase exposure in Post Production
  • Noise reduction in camera is not effective
  • Post production noise averaging works well when the subject is stationary and a tripod is available
  • Auto ISO has a tendency to push the ISO higher than necessary and should be avoided in low light situations


Ok, that's pretty much what I've learned over the last couple of days. Please let me know if I'm incorrect, missing anything critical, or need to do more reading!

Thanks.

Replacing my Canon 7D, Tokina 12-24mm, Canon 17-55mm, Sigma 30mm f/1.4, 85mm f/1.4, and 150-500mm with a Panasonic Lumix FZ1000. I still have the 17-55 and the 30 available for sale.

  
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Idiot ISO and Numpty ISO
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