greg_adkins4

I started <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?

msg_id=004PZV">a thread</a> last thursday with a question about an

image I was uploading and discovered something disturbing. A few of

the posters mentioned they had removed their photos due to the re-

compression that occurs after uploading an image to PN. Before

uploading my image, I took care to heed the <a

href="http://www.photo.net/photo-posting-guidelines">Guidelines on

Allowed Number and Size of Photos</a>, and made certain that my image

was less than 800 pixels in the long dimension as well as under the

file size limit of 100k. I too, discovered that my image (with size

of 600x601 pixels and file size of 88k) had been compressed to a file

size of only 16kb! For a comparison, please view the <a

href="http://www.photo.net/photodb/photo?

photo_id=1095422&size=lg">image on PN</a> and the <a

href="http://www.gregadkins.com/temp/dos_torres_pn.jpg">image on my

Web server</a>.

 

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It's my understanding that the larger sized image should be the same

size as my original, and I'm assuming (albeit maybe incorrectly) that

since the image I uploaded was under the 100k requirements, it need

not be compressed an additional 82%. I wouldn't be bothered by this,

but by doing so, the image displayed shows a disturbing amount of

jpeg artifact compared to the original.

 

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The PN community serves a tremendous amount of images and there's a

limit of 200 per user presumably to keep disk space under control.

That's completely understandable. However, I haven't even begun to

push the upper envelope of my allotment, and I'm finding that the

quality of my images are suffering due to the re-compression.

 

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I don't wish to complain. I just want to understand why this is

neccessary to the extent of compromising image quality. I spend a

very short amount of time on this site compared to other users with

many more photos, comments, and contributions than I, and just want

to assert the situation and possibly stimulate a review of the

current policy regarding image uploads.

 

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Maybe the guidelines should only be modified to more accurately

reflect what happens to an image after it's uploaded (for those who

are interested, of course). Again, if there's a compelling reason for

the re-compression, I think many of us would just like to understand

the reasoning behind it. So, does anyone have any suggestions, or am

I totally off base? I just don't want to hear any more stories about

people removing their images from the best online photo community

because they fear what is happening to them after they've been

uploaded!

Thanks for pointing that out, Jim. Now, your first response makes a lot more sense to me. Ha!

 

One thing I've just noticed is that the "jagging" appears only when I view the image on PN! The responses have helped me delineate the difference between "jagging" and "artifact" and I can now confirm that this is not artifact. In my original post I was referring to the "jagging" and if I right-click on the "large" image and select "save image as", I don't see the jagging! This really confuses me, but I guess it must have something to do with the way PN handled my uploaded image. It doesn't show "artifact" like Sorin's excellent example, but it shows the "jagging" or a sort of "anti-aliasing" on steroids.

 

Ok, I've definitely learned a lot here, and if anyone can lend any additional insight as to what's happening here, that's a bonus!

 

Thanks to everyone for their thoughtful responses!

Just to keep things on track, let me just state that this is <b>not</b> about what happens to my images after they are uploaded to PN. I want to know what I can do to prevent the jagging <b>before</b> I upload them to my folder.

Sorin's posts make a valid point, and it appears that PN does re-compress images (as stated in the image submission guidelines), but I've verified that the "jagging" exists by viewing my jpeg before I upload my image to PN. I'm just trying to prevent this from happening on my end before I upload new images.

After reading the above responses, it seems as though what I'm terming "artifact" is actually "jagging". This is appearing along the border defined by the sky and the two objects, as well as on some of the sharp lines on the objects themselves.

 

I've only resized my image as described. I haven't used any downsampling techniques, and I've tried maximum quality (lowest compression) in saving my jpegs, but to no avail. The reason this is puzzling me is because I don't see this on the images I've viewed on PN. One thing I have noticed is that when I zoom in PS, sometimes the image can appear jaggy, depending on the zoom factor. Does this sound familiar to anyone?

 

I know this could be a common occurrance, but what could be causing this using the techniques I've described? Is there an effective way of eliminating this?

 

Thanks for your replies.

Oops! This image was resized to 400 pixels in height, not 600. My mistake. I'm not sure why the second link didn't work for you, Jeremy. Why would the small size contribute to the jaggies? I've tried image sizes from approximately 70kb to 100kb as well and they still appear.

I'm having trouble with jpeg artifacts in this <a

href="http://www.photo.net/photo/1095422">image</a>

I've uploaded to PN. I scanned this at 600dpi using an Epson

Perfection 2450 Photo scanner. I used "Save for Web" in PhotoShop 6

to resize the image to 600x600 and save in jpeg format. I've tried

many different levels of compression and I've even tried scanning at

300 and 800 dpi, but I can't seem to get rid of the artifacts.

Interestingly enough, I have successfully uploaded this <a

href="http://www.gregadkins.com/gallery2/dos_torres.htm">image</a>

(although it has a border and is slightly smaller) to my website.

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What can I do to clean up the artifacts in this image? Should I be

using a 3rd party jpeg compression tool like Jpeg Explorer instead of

PS? I'm trying to keep the size under 100k as specified by the PN

guidelines. Is this absolutely neccessary? I'm sure PN will

compress my image if I don't, but if that's the only way I can get a

clean image...how can I tell?

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I've searched the archives, and there's so much on jpeg compression,

etc., but I can't seem to locate an answer. Please help!

Short answer: Good to excellent. Long answer: It depends. Seriously, though, you can find some old folders that will take some excellent pictures. I've had experience with several German, American, Russian, and Japanese folders and have gotten good results with 6x6, 6x9, and 645.

 

My advice to you would be to get the best model camera you can find. The lower end folding cameras are mediocre at best, so try to stay with a four-element lens. This is not to say that they aren't worth anything, but with a little research on the web, you can pick out the better from the good. The four-element lenses of the Tessar formula will perform best at f/8 - f/16. Some good ones are: AGFA Solinar, Voightlander Heliar or Color-Skopar, and of course the Zeiss Tessar. I don't want to start an argument about Russian camera quality again, so you can visit the numerous threads on this site if you're interested in a Moskva or an Iskra.

 

One essential caveat is that these cameras are usually about 50 years old, so you're going to have issues with their reliability and usability. I've learned that this is part of the fun. There are several people who fix these types of cameras and you can even get a CLA'd model through online auctions for around $150. Once you get a good working camera, you can have a hell of a lot of fun with B&W, and even color with some of the better lenses.

 

So, do some research and you'll find that there's a lot of these old cameras (even some obscure models) that will provide great results for little investment. Enjoy!

I've actually had good experience with buying new and used from Adorama. A few years ago, I bought a used Minolta MD-11 body from them only to discover light leaks on my first set of prints. When I showed them the prints, they had me walk over to their repairman one block away who promptly fixed it (in a few days) and gave me half price on a CLA ($20). Yes, I guess it was initially defective, but they can't possibly be expected to know all the problems with their used equipment, and they dealt with mine satisfactorily. I've also found their prices on new items to be comparable with B&H, and when B&H doesn't have the item in stock, Adorama does! I'd buy your Nikon with confidence!