Black Objects

Quote:

---

Originally Posted by ajohnw

Posting ProPhoto? Pass on what that might do.

---

An interesting comment, John. Took me a while to realize that the OP's camera shots do have the ProPhoto profile embedded. It might not do much - in view of the posted images being almost grayscale, in other words with no highly saturated colors to get clipped during conversion by the CMM to sRGB?

Here's a couple of saves from the same RAW shot, one ProPhoto, the other sRGB, both JPEG:

http://i62.tinypic.com/30k9hxj.jpg
http://i60.tinypic.com/raorhi.jpg

Anybody see a difference?

Can't see any difference, I don't suppose they were both converted to SRGB before you posted them ??
I once made the mistake of providing ProPhoto images for a club slide show that was being presented before a fairly large audience. Hugely embarrassing, the colours were horribly distorted. I always use Photoshop's save for web which prevents me from making this mistake again. If you use this with a split view you can see the ProPhoto original and the sRGB conversion, often a world of difference. As noted though with a monochrome or principally monochrome image the differences will be marginal.

I'm on an uncalibrated laptop away from home and I can see a lot of difference easily even colour changes as well as the grey scale.

The grey scale on the 1st one covers more dynamic range. Same part on the 2nd one may have a slight colour cast. Colours in the first are generally more vivid.

The display is generally what I would call OK.

John
-

ProPhoto does have the advantage that unlike aRGB it should be able to hold colour values that are the same or very similar to the sRGB pallet. Rather a lot of it being wasted if used like that.

What I generally see when I do a conversion using my own colour management rather than what ever is in a browser could be described as a general improvement in clarity. In otherwords a generally better image. Previously this has always been from aRGB.

On the last camera shot posted I see no detail in the pentaprism area. I was in a rush to go out so not sure about that aspect at home but think it was the same and no time available to comment.

John
-

Quote:

---

Originally Posted by ajohnw

I'm on an uncalibrated laptop away from home and I can see a lot of difference easily even colour changes as well as the grey scale.

The grey scale on the 1st one covers more dynamic range. Same part on the 2nd one may have a slight colour cast. Colours in the first are generally more vivid.
-

---

Yes, John, yours and Paul's responses are living proof of what you implied earlier, that posting with a ProPhoto profile is a crap shoot. To a lesser extent, the same applies to posting with a Adobe RGB (1998) profile. Interesting that you saw the colors in the first image as more vivid. That shows that your color management or app has correctly identified it's ProPhoto profile but somehow applied quite a 'strong' transformation on it's way to your screen.

Here's the ProPhoto one for interest, posted this time with no profile at all. It is posted as a JPEG high quality YCbCr 4:4:4 (1:1). Most people's kit will assume it to be sRGB and it should look less saturated on your laptop than my earlier two images.

http://i61.tinypic.com/wrxkav.jpg

Would be interesting to see the first two images as seen on your laptop posted as screen captures from your laptop. What app. were you using to view them?

Opera Ted as always. Not sure what the OS is probably Vista might be XP. Facilities are limited and one thing that has never updated as it should is run as administrator so I don't install here as I am using a neighbours wifi. As far as I'm aware I can't take screen shots and if I could rgb values would probably display differently elsewhere. All I can say on that score is that images look ok and nothing for me to scream about.

All I use it for is tethering my Canon's and when taking shots with a microscope camera plus some heavy optical design software at times. There is also a few bits of astro software on it and the Oly update utility and I use it when away from home. 17in display and 2 250gb disks from Dell. For what I use it for I am tempted to reload XP and re install what I use but it takes a long time on windows so haven't bothered.

Just noticed the label - vista.

John
-

ISO 200, f/8, 1/125sec, flash.

http://i57.tinypic.com/sl35lf.jpg

Comments ref post #47:

Original posted image resized and given a grayscale profile:

http://i57.tinypic.com/28knf6a.jpg

Looks a bit contrasty, white lettering is blown.

PSE6 histogram tells the tale:

http://i60.tinypic.com/2mh8k8o.jpg

On my less than perfectly set up monitor, the shadow contrast is very low although it is not actually clipped to zero. The histogram median value of 29 is telling us that most of this image is log2(29/255) = about 3 stops down from white!

So, I applied quite a drastic curve:

http://i61.tinypic.com/21cbg5i.gif

Effectively, the shadows gamma was increased and the highlights gamma decreased. Probably a bit over the top, just to make the point. Similar shadow uplifting can be done by increasing the gamma slider in Levels but the highlights would have gotten scrunched up even more.

And so for the result:

http://i62.tinypic.com/25gb5si.jpg

My feeling is that this image could survive a black background whereas the original might not. I was particularly pleased with the texture that appeared in the shadow of the lens and with the increased definition of the viewfinder housing.

Comments welcomed.

Ted,

Nice edit, surprised about the comment of blown highlights in lettering, used LR to adjust and moved sliders well beyond indication that highlights were acceptable. I left the shadows as they were as the image didn't have any significant dark values. I know between your edit and mine, yours would be much easier to print.

Quote:

---

Originally Posted by Shadowman

Ted,

Nice edit, surprised about the comment of blown highlights in lettering, used LR to adjust and moved sliders well beyond indication that highlights were acceptable. I left the shadows as they were as the image didn't have any significant dark values. I know between your edit and mine, yours would be much easier to print.

---

A possible explanation is that, when I opened your image in PSE6, it said that the embedded profile was invalid. But I opened it anyway. Which means it was opened non color-managed. So, any comments I made about tone levels could be taken with a pinch of salt. The letters were definitely RGB = 255, 255, 255 and the lowest tone in the shadow of the lens was RGB = 1, 1, 1.

I loaded the 2nd one you posted into RT as that is on my laptop. Not sure if this one is prophoto or not but RT works in prophoto so should take it straight to sRGB. There is a lot of black clipping, not just single channel clipping, lots were all are clipping so can't do much with it.

;) I'm posting this more so that I can see what it looks like on a proper monitor. Quick curve to increase black contrast and a bit of lab contrast. Lot of highlight compression to damp down a patch in the background. Maybe too contrasty on this machine but not much time available.

http://i62.tinypic.com/4lhqqe.jpg

John
-

Quote:

---

Originally Posted by ajohnw

I loaded the 2nd one you posted into RT as that is on my laptop. Not sure if this one is prophoto or not but RT works in prophoto so should take it straight to sRGB. There is a lot of black clipping, not just single channel clipping, lots were all are clipping so can't do much with it.

---

It was Prophoto, John.

Interesting comment about the black clipping.

Opened in PSE6 there was no black clipping at all (PSE6 honors ProPhoto but can not assign it or convert to it).

Opened in RT 4.2.3, 'neutral' camera profile, 'use embedded if possible' selected and with ProPhoto working space of course, there was only a bit of black clipping, mostly reds - although the histogram was indeed heavily biased towards the dark end.

I was using 4.1.39. Better with use embedded but still far to much all channels clipping shown in luminosity mode. Colour mode shows any channel clipping and getting completely rid of that can leave images rather flat sometimes but there isn't much dynamic range in this shot really even though there is slight high light clipping.

I'd guess that RT has Little CMS in it. Hard to believe it has mistakes in it so it's odd that PSE shows no clipping. On the other hand lots assume LR uses prophoto but it turns out it uses something Adobe.

One explanation about the clipping could be down to RT. I believe it's levels are set above zero to account for back lit screens. Wise move if gradation is to be seen in blacks.

John
-

Maybe you should compare the used tresholds for clipping.

George

Quote:

---

Originally Posted by ajohnw

I was using 4.1.39. Better with use embedded but still far to much all channels clipping shown in luminosity mode. Colour mode shows any channel clipping and getting completely rid of that can leave images rather flat sometimes but there isn't much dynamic range in this shot really even though there is slight high light clipping.

I'd guess that RT has Little CMS in it. Hard to believe it has mistakes in it so it's odd that PSE shows no clipping. On the other hand lots assume LR uses prophoto but it turns out it uses something Adobe.

One explanation about the clipping could be down to RT. I believe it's levels are set above zero to account for back lit screens. Wise move if gradation is to be seen in blacks.

John
-

---

My mistake - I examined the wrong image. The one you looked at had about 1700 counts at zero luminosity in PSE6. Sorry :(

RT defaults to showing clipping at 8 bits which where back lit panels start to work reasonably well but maybe a bit high for a well set up monitor. If I can I try and set the darkest end to 7 bits minimum and 6 at a pinch. With the indicated clip level set to 0 RT gives this.

Any channel clipping in R, G, or B.

http://i60.tinypic.com/doo41c.jpg

All channels clipping, marked as blue.

http://i59.tinypic.com/2zybfyd.jpg

I think the camera needs a good clean John. I didn't convert this one, just reworked from the original and added an sRGB profile I hope. One thing i needed to fix was a slight blue cast in some of the blacks Not sure if it's completely out on this.

http://i60.tinypic.com/wbrwig.jpg

mmm It needed a bit more contrast really.

John
-

Why not 0? In my remembering the treshold is mainly ment fot printing. Or make it 1 or 2 to see the difference between black and real clipping.
I installed RT on my pc and it's standard 8, in CaptureNx it was 3 and I had to download a new one and there it's 0.

George