Why'd This Happen - Polarized / Posterized?

[slejhamer]

Why does this very odd posterization effect occur?

The only post-processing was resizing for the web and modest sharpening (amount 60, rad 0.3, threshold 2 - just enough to offset the softening that occurs when resizing); otherwise it is straight out of the camera.

In-camera settings were all "normal" (i.e., saturation, contrast and sharpness.) Handheld at 1/50s, f5.6, 50mm.

I did use a polarizer, which could explain the intense saturation, but why the posterization?


http://members.cox.net/mschlesinger/04202003_003%20copy.jpg

[Conk]

What is posterization?http://www.adimaging.com/forums/images/smiles/icon_confused.gif

[slejhamer]

It looks like paint-by-numbers in the color areas. The best example is the foreground center flower, but it's there throughout. Not very much detail in the petals.

Notice that the relatively muted colors in far background look normal. That area was in shade; I wonder if the bright afternoon sunlight, combined with the polarizer, was just too much for the camera's sensor?

[Conk]

Is posterization and the deep saturation 1 in the same?
You say it may be the intense sunlight. It seems to me the deep saturation is mostly with the purple. The purple would likely obsorb the light while the red would reflect it.

[john_houghton]

Mitch, I don't see any link to the image being discussed. Where is it?

John

[slejhamer]

LOL! They're not supposed to look quite so red - the real flowers were a soft orange! And yes, the purples are too deep (and reddish?) as well.

But no, I don't think saturation and posterization are the same, although I guess the saturation may in fact add to the posterized appearance, so you may be on to something.

In the other image I posted of the girls on the bench, the colors are still very deep but also more accurate - those reds were in fact red (different tulip variety.) As I mentioned the sunlight was much less intense in that part of the park - in fact, at that time, it was getting a little overcast and the light more diffused. Here, an hour earlier, the light was harsh and direct.

So, unless someone can better explain the technical side of things, I guess I will conclude for now that the posterization was caused by a combination of hard direct sunlight, the deep saturation (enhanced by the polarizer,) and the limited dynamic range of a 3mp consumer digicam... :(

[slejhamer]

JOHN:

Try refreshing your browser. I just checked on an offsite computer and it seems to be working... sometimes I notice the site (hosted by my cable company) goes down during the day, so maybe you have a stuck page in your cache.

Here's the direct link if not:
http://members.cox.net/mschlesinger/04202003_003%20copy.jpg

[john_houghton]

Mitch, Thanks, I see the image now, though I'm not sure I see much of a problem. I would like to know if the posterization is evident on the original image before it was resized downwards. Or did it appear after resizing or after saving to jpg? If the image is intended for viewing on the web, then how did you save it to jpg? It still has the exif data in the file, which it shouldn't, and the embedded profile is "ofoto", so you should really convert the colour space from that to srgb and then use Save for Web in Photoshop. This will give slightly different colours to your present file when viewed in a web browser, (and also a smaller file).

John

[slejhamer]

oops! must have hit the wrong "save as" action and gave it my online printlab profile instead of srgb... :O

Wrong profile aside, the posterization is very evident in the original (a superfine large jpeg, not raw this time.) Aside from any color shifting (there is not much, really) what you see is very close to the original. The issue isn't really hue shifting or the saturation, though, but the large blocky (posterized) look. But thanks for saying you don't see much of a problem! :)

When I save a jpeg I use 'save as copy' in PS and it always retains the EXIF data. This was at level 9 compression (high quality.) I tend to target around 100kb in file size, and haven't used the save for web function. (I did try it once and saw lots of jpeg artifacting, so stopped using it. I should try it again... )

Thanks!

[dn7elson]

Seems that we both visited Medowlark recently ;)

Here is the image from my G2.

http://www.pbase.com/image/15884831/large

I did have a couple of shots that seemed to do what yours did, but upon closer examination of my images, found that the focus ended up on the foliage and not the flowers, so they were slightly out of focus, causing either a blooming effect or the polarization you cite.

[slejhamer]

Dale - you clearly have exceptional taste in parks and a great eye for composing a flower scene! Yours seems better exposed than mine. Nice.

That new footbridge by the pond should make a great portrait setting when the willows fill out.


___________________

I think I will play with this one in PS and convert it to a watercolor, then print it on a textured paper. Should be good for that, given the look it already has.

Thanks,

[dn7elson]

slejhamer wrote:
That new footbridge by the pond should make a great portrait setting when the willows fill out.


The footbridge is a pleasing structure and provides a bit more stable (albeit less exciting) landing than the loose rocks that previously made the pond crossing possible.

Here's a Fall shot from the shore at the new bridge.

http://www.pbase.com/image/15891424

[slejhamer]

Nice Dale! That reminds me - it's good to see the water at higher levels now, after last year's drought. And yes, I liked the rock path through the water too - my 3 year old was sad to see that it was gone.

P.S. Did you notice the 33% increase in the admission price? I guess that bridge needs to be paid for...

[dn7elson]

slejhamer wrote:
P.S. Did you notice the 33% increase in the admission price? I guess that bridge needs to be paid for...

We have gotten the annual pass the last couple of years, which I think has been the same as this year, so I really don't remember the per visit rate.

With the annual pass, we can spend an hour or so taking pictures and then leave without feeling that we have to stay longer to justify the fee.

We did the same when we lived in San Diego with the Animal Park. We could just go for a picnic lunch and take some pictures whenever we felt like doing so. Otherwise, it was a daily rate of $20 each, making you want to spend the entire day to offset the cost for the four of us.

[slejhamer]

Ha! - I didn't know they offered an annual pass. I guess that makes sense; I get one for Great Falls, and it's all the Parks System. Thanks for the tip.

Funny, I used to live in So. Cal too. Small world.

Regards,

[PaulB]

Oversaturated colour therefore out of gamut - ie. range that can be handled by the various parts of the system (monitor, printer etc).

See "Identifying out-of-gamut colors" in Photoshop help.

You should be able to partially correct the problem in PS.

Hope this helps.

[slejhamer]

Paul, that makes perfect sense.

I will guess that this was out of gamut for the camera (and thus a limitation in the original image file) as reducing saturation in PS only helps a little.

Thanks.

[PaulB]

Nice photo thoughj