Nentralisation picker inconsistent in Phocus

Andre Regini · January 31, 2009, 05:15:55 AM

Been playing neutralising the same image in Flex and Phocus shot with a QP card in the image.

On a QP greay card Flex gives me a consistent colour temp of 4800 and a Tint of -2 wherever I pick within the grey area. However the same image in Phocus gives me anywhere between 5100K and a tint of 16 and 4600 and a tint of -19. So far it's always looked wrong.

What's going on? Anyone else tried this?

Andre

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garyros · January 31, 2009, 07:37:03 AM

What is a QP Grey Card?

Eivind Røhne · January 31, 2009, 08:56:38 AM

Hi Andre,

Had to try it when I read your post. Tried it on one test image, and I don't get inconsistent readings, but I don't get the same white balance as in Flex... Weird. Flex says 5300/33 and Phocus claims 5350/37 from exactly the same spot on a Gretag Macbeth card...

Gary: A QP card is a card for neutralizing color. Looks like a thin PostIT block, and you can tear off one grey card at a time, and it comes as three patches (black, grey, white) or cards with lots of color patches if I'm not mistaken (www.qpcard.se). Correct me if I'm wrong. I always carry a block of the three patched version as a back-up in case I should lose my Gretag.

Andre Regini · February 02, 2009, 01:31:55 PM

Hi Eivind

If you get the chance, tell me what you get with the FFF file at www.kingbridge.co.uk/temp/greytest.zip. May be a PC issue.

Andre Regini

garyros · February 03, 2009, 02:46:35 AM

We sell a digital gray-card. I have always found them to be fine. I have also used the Lastolite fold-out system too to work well.

Thanks.

Gary

Eivind Røhne · February 03, 2009, 03:20:58 AM

Hi Andre,

I get lots of different results around the grey area, ranging from 4600/-19 to around 5100/2. I zoomed to 400%, and then the grey card looks a little bit "dirty" or "grainy". When zoomed in, I tried neutralizing in the upper left part of the grey, on two neighbouring pixels (I chose two pixels right next to each other that look identical on screen, with no grain/dirt). And even then I get the two extremes 4600/-19 vs 5100/2 even though they are "identical neighbours". Weird...

Send an email to phocus@hasselblad.dk (and support@hasselblad.dk) with a link to the file you sent me, so they can download it and do some testing. And keep us updated here Andre!

NickT · February 03, 2009, 08:18:56 AM

Quote from: Andre Regini on January 31, 2009, 05:15:55 AM
Been playing neutralising the same image in Flex and Phocus shot with a QP card in the image.

On a QP greay card Flex gives me a consistent colour temp of 4800 and a Tint of -2 wherever I pick within the grey area. However the same image in Phocus gives me anywhere between 5100K and a tint of 16 and 4600 and a tint of -19. So far it's always looked wrong.

What's going on? Anyone else tried this?

Verrrrrrry interesting...

First off a quick rant I find the QP cards pretty useless, they metamarise and gather dirt very quickly, plus the black patch and grey patch are not equally neutral. /Rant

I think I know what you are seeing and it all comes down to sample size.. I bet when in flexcolour you are sampling from the main image rather than in the detail window yes? I further suggest that in Phocus you are sampling at 100% view in the main window.. (sounds like a line from Court TV) What you are seeing is dirt on the QP card throwing off the reading when you are sampling the card close in, when zoomed out in Phocus I see very little difference in the readings across the gray patch just as I do in the main window in Flexcolour.
Make sense?
Nick-T

Andre Regini · February 04, 2009, 06:10:50 AM

QuoteVerrrrrrry interesting...

First off a quick rant I find the QP cards pretty useless, they metamarise and gather dirt very quickly, plus the black patch and grey patch are not equally neutral. /Rant

I think I know what you are seeing and it all comes down to sample size.. I bet when in flexcolour you are sampling from the main image rather than in the detail window yes? I further suggest that in Phocus you are sampling at 100% view in the main window.. (sounds like a line from Court TV) What you are seeing is dirt on the QP card throwing off the reading when you are sampling the card close in, when zoomed out in Phocus I see very little difference in the readings across the gray patch just as I do in the main window in Flexcolour.
Make sense?
Nick-T

Hmmmm... opened in the image in Flex (PC OS) and on my system, the neutarlisation picker doesn't work in the Detail window and no matter what zoom I use in the main window, I always get 4800K & -2

However... I converted to DNG and tried PS. On low zoom levels I get a consistent 4800K and -1. However when zoomed right in, it's all over the place. 4700K -3 to 4900 -1 (not as much as Phocus tho).

Pretty convinced that it's down to sample size. It think Flex has a consistent sample size (no idea what), Phocus uses a point sample and PS's sample size depends on zoom level.

Why isn't there a method to alter the sample size? Years and years ago I tried Paint Shop Pro. A cheap cheap package, but that had a superb dymanic sampling tool. You could marque select an area, it would average it, and you could then netralise it, or make it match any colour or preset skin tones.

Camera's are not noiseless and the amount of noise varies depending on conditions, so why can't we alter the sample size on a neutralisation picker?

Andre

NickT · February 04, 2009, 08:41:57 AM

Hi Andre
First off, to use the neutralisation picker in the detail window in Flexcolour; first select the picker then press and hold option/Alt and it should work. You can thank me later.

Second I agree, some control over sample size would be very useful or at the very least some indication of what it's set at.
Nick-T

Andre Regini · February 05, 2009, 10:48:05 AM

Got this back from Hasselblad..

"yes there appears to be an issue effecting
some users with certain graphics card configurations ,
which R&D are not 100% certain of at this point in time ,
But there will be a fix in the next update."

Thanks Nick. Yep found that later, well found it's the control key on a PC system.

Tried sampling around that area in the detail window and getting similar results to the DNG in PS at max zoom.

So it seems that in Flex you can choose a large sample area using the standard window and a small one using the detial window. In PS sample size depends on zoom level and in Phocus the sample size is set small (too smal in my opinion). I would always choose to use a significant sample size for this type of process. There will always be some noise and it will always vary from image to image, so having a significant sample size is important. Ideally you ought to be able to configure it to suit, be nice if this were sorted in the next version of Phocus as well as the graphics card issue.

Andre

NickT · February 23, 2009, 07:45:54 AM

FYI the latest beta readme states that the sample radius for the neutralisation picker has been increased.
Nick-T

Andre Regini · March 03, 2009, 07:33:49 AM

Been assured that in the next version of Flex the picker size will be adaptable.

Does anyone know what size it is now? I was told at Focus, but can't remember if it was 3x3 or 9x9. I think that 3x3 is still too small, esp if the iso's now been pushed to 800.

Andre Regini

justalex · March 24, 2009, 11:17:14 AM

In my experience it's the sample size.

Trying to do a balance on an image shot at higher ISO is impossible due to the colour noise. Readings can vary dramatically.

Can't believe they still dont have a variable sample size in Phocus yet.