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Thread started 17 Nov 2007 (Saturday) 21:26
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Apple Aperture & 40D RAW HTP & ISO experiments

 
rkkwan
Member
134 posts
Joined Sep 2007
Location: Hong Kong
     
Nov 17, 2007 21:26 |  #1

With OSX 10.5 and 10.4.11 supporting the 40D RAW, I decide to do some experiments to see how Apple's Aperture handle Highlight Tone Priority (C.Fn II -3) when it comes to RAW files. I've also read about clipping issues with some ISO settings, so I decide to check those out too.

I shot my ceiling lights with my 40D and 50/1.4 in RAW. WB adjusted to 2,837K, -26 in all pictures.

First, HTP. Immediately I discovered the serious bug that's been reported on dpreview and on Apple's discussion boards about the 40D and 1DIII. Some people say extreme highlight becomes yellow or blue. Well, here it is:

ISO400, 1/200, f/5.6, HTP on; RAW Fine Tuning 1.1

IMAGE: http://rkkwan.zenfolio.com/img/v2/p524107996-3.jpg

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IMAGE IS A REDIRECT OR MISSING!
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The whole big cyan spots on the picture has R:0, B:255, G:255. The spike in the middle of histogram has R around 128, which are pixels right on the edge of the cyan spots.

Interestingly, I found that if I change RAW Fine Tuning to 1.0, this bug is gone:

ISO400, 1/200, f5.6, HTP on; RAW Fine Tuning 1.0
IMAGE: http://rkkwan.zenfolio.com/img/v2/p390868600-3.jpg

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


Now, turning off HTP, no change in picture or histogram. [I'm showing you RAW Fine Tuning 1.1, but no difference if I use 1.0.]

ISO400, 1/200, HTP Off; RAW Fine Tuning 1.1
IMAGE: http://rkkwan.zenfolio.com/img/v2/p377552264-3.jpg

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


Next, I'll show the pictures and histograms if I pull back 2 1/3 stops.

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rkkwan
THREAD ­ STARTER
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134 posts
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Location: Hong Kong
     
Nov 17, 2007 21:49 |  #2

Here's what it looks like when I pull back exposure by 2 1/3 stops in Aperture. That's basically all the info I can get. Nothing else to the right.

I did not include HTP on, with 1.1 because the cyan patches interfere with checking the highlight areas.

HTP on, RAW Fine Tuning 1.0

IMAGE: http://rkkwan.zenfolio.com/img/v2/p214379794-3.jpg

Full size image at http://rkkwan.zenfolio​.com/img/v2/p214379794​.jpg (external link)

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


HTP off, RAW Fine Tuning 1.1
IMAGE: http://rkkwan.zenfolio.com/img/v2/p139186234-3.jpg

Full size image at http://rkkwan.zenfolio​.com/img/v2/p139186234​.jpg (external link)

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


HTP off, RAW Fine Tuning 1.0
IMAGE: http://rkkwan.zenfolio.com/img/v2/p147624336-3.jpg

Full size image at: http://rkkwan.zenfolio​.com/img/v2/p147624336​.jpg (external link)

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


Now, there are differences in the color artifacts around the most blown areas, but overall exposure seem to be the same in both highlights and shadows for all three. HTP doesn't seem to store more info or affect how Aperture interprets the data. In fact, shooting with HTP off and using RAW Fine Tuning 1.0 seems to get more detail than 1.1.

That's my impression. But the experts may want to chime in here. At this point, I don't think there's benefits in shooting with HTP on, if one's shooting RAW only and uses Aperture for PP.

Next: ISO issues.

rkkwan.zenfolio.com (external link)
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rkkwan
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Location: Hong Kong
     
Nov 17, 2007 22:48 as a reply to  @ rkkwan's post |  #3

Now, here's something I understand even less, but is not confined to Aperture. Should matter to all users of the 40D, or even all Canon dSLR users.

I've read on various threads on dpreviews and here about "native ISOs" for the Canon dSLRs, as well as what ISO to use, what to avoid. Well, since I was doing the above experiment already, I decide to shot a couple extra shots.

Basically, I can confirm one fact. ISO 160/320/640/1250 are different from the other two sets of ISOs. Some people have observed that the above set clip earlier, so they should be avoided. Others have observed that the above set has lower noise level than others, so should be preferred.

Now, back to my ceiling lights. Here's what I've shown before, ISO400 1/200 f/5.6. [Everything with HTP off now, all with RAW Fine Tuning 1.1.] Minus 2 1/3 stops on Aperture:

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


Maintaing exposure, ISO500 f/6.3 looks basically the same:

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


But look at ISO320 f/5:

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


Initially, I thought that was a bad thing with ISO320. But then I look at the highlight areas in the photos at original exposure:

ISO400 f/5.6
IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


ISO500 f/6.3
IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


ISO320 f/5
IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
HTTP response: NOT FOUND | MIME changed to 'image/png' | Redirected to error image by ZENFOLIO PROTECTED


Less highlight is blown with ISO320 at identical exposure, and if I pull back exposure in Aperture, I can recover just as much blown highlights with 2 stops for the ISO320 file as I can with 2 1/3 stops for the ISO400 and ISO500 files.

So, practically, I don't see any downside with using ISO320 (which should apply to ISO160, 640, 1250 as well); and if the reports of less noise at these ISO settings are correct too, then these should be the best ISO to use, and not to avoid.

Am I right or wrong?

rkkwan.zenfolio.com (external link)
5D/BG-E4; 70-200/2.8L IS II, Sigma 8-16, Tamron 28-75 Asph, Tokina 10-17 Fish, 1.4x III; 580EX II; G7 X
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Apple Aperture & 40D RAW HTP & ISO experiments
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