Saturday, December 29, 2007

Observations on photographing art and color gamut


Normal people may want to skip this one. It is just a technical note.



Recently I did some experiments on photographing art, in this case watercolors. Unlike "normal" scenes that involve natural things, faces, hedgehogs and dogs, when you start to wander into the area of paints, you can get some pretty intense colors. As part of a larger experiment on understanding how to accurately photograph art, I thought I would investigate some gamut issues.



To do this, I placed two watercolor paintings, a set of "full strength" tube watercolor paint swatches (Daniel Smith, if you need to know) and a grey card in my living room under well lit, cloudy indirect light. The art was photographed with Nikon D80, with a Nikkor 18-200 lens set at 50mm (75 mm eq. for 35mm) at f8 in raw (.nef) mode.



The first time I entered Photoshop camera raw (ACR4), I set the white balance on the illuminated part of the Kodak 18% grey card. This seemed to correspond to a color temperature of 4950 K. The camera's "guess" at the white balance was 5000K. Both of these proved to be too "cool", and this is not unexpected, as normally we think of cloudy as about 6000K. I then set the white balance on the white paper itself. This came in at 5800, which is closer, but (no surprise) rendered the paper as white when in reality it is slightly warm. When I chose 6100K on the slider, the paper color looked about right on the monitor. As it happens, when subsequently printing, this still resulted in a printed color still a bit bluer than the actual paper. But this blog is not about color matching, it is about gamut, so I will stop.



I converted the image into Adobe RGB, 16 bit, and then looked at it in photoshop. I then set up to proof these under a variety of conditions, and looked at where I found out of gamut colors come up. But first, a reminder - even though I am in a wide color space, the camera could have already clipped some colors, and I would have no way of knowing. However, given that in general the printer gamuts are often the most limiting, and given what I found, it seems to me that this was not the case here.



First, I selected an output space of sRGB, and looked at the gamut warnings. As it happens, this space was the most restrictive - it clipped parts (perhaps about 5%) of the watercolor paintings, especially blues and oranges, little bits of the golden wood, and about 20% of the full strength color swatches. Here is the gamut display, with the clipped colors shown as grey patches or dots:

It is also useful to note that since for web display, you render everything in sRGB, so the photo that appears at the top of this blog entry has already been clipped per the areas above - but at the same time, you can look to see that such clipping is not horrible, it just makes them less intense than in real life or when printed on a good printer. Also note that this first picture (and not the clipped gamut demo pictures) is the only one that is color managed properly at all - you can see that the paper itself is not white, but should show slightly warm.

Next, I selected my inkjet printer (HP D7160) with HP Premium plus glossy paper. This left everything unclipped except the full strength ultramarine blue color:




Next, I selected a profile I use for printing at Adorama. They print on Kodak Endura, a professional color print paper, and use the best processing machines out there. Here, there was some moderate clipping, a bit better than sRGB, but not as good as the inkjets:




Finally, I selected the profile from EZPrints (a profile I had downloaded a while ago) - they are also an online printer, and I think (but am not sure) that they offer prints using pigment ink. These can (if they use a 7 or more ink system) produce a somewhat wider gamut. Regardless of which printer they have, there was no gamut clipping in this case.


Monday, December 17, 2007


Those who know me.....

... know how true this is:

Thursday, December 06, 2007

New "safe" feature - Child-safe caps on Water bottles??????

At our company open-house, I picked up a small container of Polish Spring bottled water to drink, and turned the twist cap. Nothing happened. Turned it again - couldn't figure out how to get it open, even though I have been doing this for years.

I then noticed the label proudly displaying the "Child-safe twist cap!" safety feature. Huh?

My first thought was "why, do they need to protect the kids from accidentally drinking the water? Is water that harmful? I try pushing and turning the cap, the standard way of opening child-proof things - no luck.

Then I notice the entire cap on the bottle is turning. Now I get it. On further reading, The Child safe feature, says "non-removable cap reduces the risk of choking" Yeah. Right. Caps are pretty big things - if this is a risk, there are a whole LOT of things that would have to be eliminated from the world first.

With this, I now know what I need to do - hold the lower cap with my hand, then turn the upper to break an almost-invisible plastic tab. From then on, things worked normally.

Nope, I don't think this has to do at all with child safety. It has to do with preventing people from refilling the bottles - if you can't get the cap off (and you can't!) you can't refill the bottles.

I hope this doesn't catch on....

Saturday, December 01, 2007

A leisurely Sunday

Well, last Sunday, actually. The previous week had been busy. I took Tuesday and Wednesday off from work, giving me a full week free. On Tuesday, we went to visit my mom in Lakewood. She is doing quite well, actually. We returned late at night, and the next day G's mom and brother drove up from NJ for a visit. We had a good Thanksgiving meal on Thursday, Tim treated us to a nice dinner out on Friday, and I cooked dinner on Saturday. Eat, Eat Eat.

On Sunday, we were back to ourselves, just the two of us. We embarked on some causal birding along the Lake Ontario lake shore. Here is a list of what we saw:

  • Hood Merganser
  • Red-breasted merganser
  • Ring-billed Gull
  • Canada goose
  • Mallard
  • Herring Gull
  • Redhead
  • Common Merganser
  • Scaup (greater or lesser we do not know)
  • Great blue heron
  • Black-capped chickadee
  • Red-breasted woodpecker
  • American crow
  • Greater black-backed gull
  • American robin
  • European starling
  • Red-tailed hawk
  • House finch
  • Mute swan
  • Double-crested cormorant
  • Mourning dove