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350D: pixelated images

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markn7

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hello there

i have a 350d and am having some problems with pixelated images. the problem is with dark areas of the images. its not compression because the pixelation is there with the full resolution image converted from raw. anyway, here are some jpeg versions and crops to better show the pixelation. if anyone could help me out as to where i'm going wrong, it would be much appreciated. thanks







 
markn7 said:
i have a 350d and am having some problems with pixelated images.
the problem is with dark areas of the images. its not compression
because the pixelation is there with the full resolution image
converted from raw.
Click to expand...
Converted from RAW to what? I dont see anything much other than minor compression artifacts. There is also a little noise in the darker areas, but generally the images look quite clean.
markn7 said:
anyway, here are some jpeg versions and crops
to better show the pixelation.
Click to expand...
I'm not sure what you mean by pixelation in this case.

Brian A.
 
i convert the images from raw to uncompressed tiffs in ACR. perhaps i should have shown you larger images, but there is a lack of smooth progression of shades and instead large blocks of dark pixels.
 
markn7 said:
i convert the images from raw to uncompressed tiffs in ACR. perhaps
i should have shown you larger images, but there is a lack of
smooth progression of shades and instead large blocks of dark
pixels.
Click to expand...
I don't see what you describe - is your monitor set up correctly (32 bit color)?
Misha
 
the skin area near the elastic under the chin doesnt look good but that maybe down to compression. Otherwise apart from the picture not being sharp there isnt much of a problem that i can see
 
That is sensor noise which will show up in dark areas of underexposed pictures or if shooting 800 or 1600. Can you you give us the EXIF on this picture? Sharpening also will make this noise more notable.

I hope this helps.
 
Thanks Tom

I was wondering whether it might be underexposure. I was thinking that the subjects are both dark whereas the background is light and that this may have led the camera to underexpose.

Here is the shooting data:

Exposure: 1/20s at f5.6
Exposure program: Shutter priority
ISO: 100
Focal length: 55mm
Flash: Fired, compulsory mode

The image hasn't been sharpened at all.
 
actually that doesn't show it any better and the website hosting it have compressed it. one can only really see the effect properly in the image is dragged into photoshop.
 
What type of external monitor are you using? I cannot see the effect you describe on my screen, but it sounds like an LCD screen that is struggling to resolve shadow detail. Most LCD screens (and I would guess that includes the iBook, although I'm not sure) are poor at showing smooth gradations of colours near black. I used to get something that sounds like what you describe, on my old LCD monitor. Now I have my nice Eizo monitor the images that looked poor before are fine on the new screen.
 
Graeme Cogger said:
What type of external monitor are you using? I cannot see the
effect you describe on my screen, but it sounds like an LCD screen
that is struggling to resolve shadow detail. Most LCD screens (and
I would guess that includes the iBook, although I'm not sure) are
poor at showing smooth gradations of colours near black. I used to
get something that sounds like what you describe, on my old LCD
monitor. Now I have my nice Eizo monitor the images that looked
poor before are fine on the new screen.
Click to expand...
I've just seen your other message, where you describe that the effect is worse in Photoshop. Are you using Adobe Gamma? That always made the effect (that I described above) worse on my old monitor...
 
I've just got a Sony SDM-HS95P. It and I haven't had any other problems except with this set of photos. Which is why I'm thinking it may be an exposure problem leading to noise.
 
i've just been checking the histograms for the both images and they both have a gap on the right hand side. so they are overexposed. but i didn't think that would result in so much noise.
 
markn7 said:
I've just got a Sony SDM-HS95P. It and I haven't had any other
problems except with this set of photos. Which is why I'm thinking
it may be an exposure problem leading to noise.
Click to expand...
The Sony is not a true 24bit colour panel - i.e. it cannot truly produce 8 bits of resolution per colour. As with many current LCDs it actually produces something like 6 bits per colour and 'fills in' all the other shades by dithering. It's not a huge problem in normal use, but IS likely to produce the type of thing you are describing. (The Sony spec is that it produces 16.2 million colours, which is typical of a 'dithering' panel. The spec for a 24bit panel is 16.7 million colours).

The fact that a number of people have said that they cannot see the problem with your images suggests that it IS your monitor(s).

Also, I went down exactly the same path myself, thinking there was something wrong with my images before I finally discovered it was the monitor :)
 
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