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Pictures on forum - low color count?
I have noticed on a lot of pictures posted, that the background is blocky and is some cases, looks like the color count has been dropped. Is this associated with the lenses, purposeful pp, or the way the forum is compressing/displaying the images?.

Thanks,Clayton..

Comments (12)

I haven't noticed that. Can you link to a specific example?Just trying to learn.

Blog: http://novicephotog.blogspot.com/Flickr: http://www.flickr.com/photos/9778447@N07/..

Comment #1

The forum doesn't compress the images. To view an image on a dpreview forum, you must previously upload it in a photo sharing site, (like flickr.com, pbase.com, picassaweb.com, etc)..

Some of those sites apply agressive compression on the image uploaded (automatically, or as a user's choice) to save space. That is why you see those blocky background or poor color transitions..

Claude Carrier..

Comment #2

Http://forums.dpreview.com/...ms/readflat.asp?forum=1030&message=27662841.

The background on the hummingbird is blocky/low color and the background of the seagulls below it are blocky as well. This appears on many pictures I see (not all) on this site...

Comment #3

The hummingbird shot looks OK to me. The two of seagulls with blue sky show evidence of JPEG compression artefacts at the edges; the pictures have been saved with too much compression. Also the noise in the sky is fairly evident; maybe these are substantial crops. Neither problem is anything to do with the dpreview site..

Best wishesMike..

Comment #4

Malathan wrote:.

Http://forums.dpreview.com/...ms/readflat.asp?forum=1030&message=27662841.

The background on the hummingbird is blocky/low color and thebackground of the seagulls below it are blocky as well. This appearson many pictures I see (not all) on this site..

Those are jpeg compression artefacts. They appear because the images have been compressed quite a lot.There are several possible reasons:.

1. Politeness. Rather than use up bandwidth with very large (megabyte) images, the file size is kept low..

2. To reduce unauthorised copying. Instead of sharing a full-size, best quality image free of charge, sometimes a lower quality version is shared..

3. Automation. A good-quality and large size image may uploaded to the hosting site. The hosting site may then automatically generate images at small, medium, large etc. sizes and may introduce additional jpeg compression artefacts..

Regards,Peter..

Comment #5

Ccarrier wrote:.

The forum doesn't compress the images. To view an image on adpreview forum, you must previously upload it in a photo sharingsite, (like flickr.com, pbase.com, picassaweb.com, etc)..

PATENTLY not true. Not to shout, but these perpetual posts insisting (or maybe assuming) that images must be posted on a photo sharing site are pure misinformation..

Yes, it is true that an image must be hosted somewhere for it to be linked/embedded within DPR forums. However, that host need not be a photo sharing site! Images can be uploaded to virtually any Web space, independent of whether that space is photo-dedicated or not..

My photo gallery is posted on my personal space that I purchase from a large Web host. It's not a photo sharing site. Many here do the same..

So while it is true true that dedicated photo hosting sites may compress images, it is untrue for those of us that host our images on raw Web space. That is, unless we choose to reduce the photo resolution ourselves..

Rant over ..

Comment #6

You're right. I over simplified the hosting part. Of course, you can have your photos anywhere you want.Claude Carrier..

Comment #7

LOL.. absolutely true. I see it all the time as well. People insisting on photo sharing sites. I host my own domains or use free space at the ISP. I load the images up the way I wish with the compression I choose..

I suppose that many people would have a hard time using an FTP client. I don't know. It's pretty easy...

Comment #8

LucyE- 510, 40-150 and 14-54 lens!U ZI owner!Olympus C30-20Zhttp://www.pbase.com/lucyFCAS Member #98, Oly Division'Photography is the art of seeing what others do not.'.

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #9

Lucy wrote:.

Could it be your computer settings?.

Good point Lucy..

Firstly, some LCD screens are not capable of smoothly displaying tones such as sky, where there is a gradual change in brightness or colour. Instead the area is shown as a uniform block of a single tone which abruptly changes to the next darker or lighter shade, with square blocky edges. This would be less visible in the more detailed areas of an image where the colour or brightness contains larger variations, but tends to affect this type of background area..

Also, but less likely these days, if the computer is configured for less than 24-bit colour similar problems arise. It's worth checking the display quality settings.Regards,Peter..

Comment #10

Looks like it WAS my monitor. Or more specifically, going through remote desktop. I remote in to my home computer from work to view this forum. What is odd is that 4/5 of the pictures seem fine and correct. Viewing images off my computer look fine as well. But 1/5 of the pictures off this forum are blocky in the background.

The fact that most pictures looked fine is what was throwing me..

FYI, for those who are not familiar with remote desktop, it allows you to connect one computer to another and control that computer as if you are sitting in front of it. The downside of remoting is that the screen redraw is horrendious. Think of loading a page with several high quality images, going ot get a cup of coffee, come back and screen is still redrawing. Yea, so it is painful. But bright side, company IT can see a remote desktop session going out, but they can't see what I am doing on my computer. Think ebay, email, this forum, *grin*...

Comment #11

Malathan wrote:.

Looks like it WAS my monitor. Or more specifically, going throughremote desktop..

Aha! This extra information we now have makes things a whole lot clearer..

In effect the remote software is taking a screen capture several times a second, compressing it heavily (not sure whether it is JPEG or GIF type compression, and transmitting it to the receiving computer..

Generally when controlling another computer, sharpness is important, as we want to be able to read text and access menus and so on. Colour accuracy usually suffers as part of the trade-off as the compression needs to be done very rapidly.Regards,Peter..

Comment #12

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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