Operation Photo Rescue's Online Community

OPR Workshop Information Exchange => Photoshop Discussion => Topic started by: Tori803 on February 19, 2014, 12:54:45 PM

Title: JPEG Compression
Post by: Tori803 on February 19, 2014, 12:54:45 PM
Many volunteers wonder why we capture photos to be restored in JPEG format instead of in TIFF or RAW. The main reason is file size. We simply can't upload, download, or store thousands of enormous files. But JPEG is not an evil format. It is well suited to average photographs as long as the photographer or restorer understands the limitations of lossy compression.

If you are interested in the technical side of JPEG, you can read more about the format at http://en.wikipedia.org/wiki/JPEG (http://en.wikipedia.org/wiki/JPEG).

Another interesting article geared toward the layman that I enjoyed can be found at http://photo.net/learn/raw/ (http://photo.net/learn/raw/), under the heading, "When to shoot RAW, when to shoot JPEG?"

Tori
Title: Re: JPEG Compression
Post by: Candice on February 20, 2014, 10:59:00 AM
 :up2: Well explained. What is ideal is not always practical. 
Title: Re: JPEG Compression
Post by: Bambi on February 20, 2014, 03:32:01 PM
Interesting articles, Tori. Thanks for posting them.

My question is: Has anyone come up with a quick way to deal with this in the pictures, or are we still healing and cloning each one?

Bambi
Title: Re: JPEG Compression
Post by: G3User on February 21, 2014, 01:29:20 AM
Thanks Tori.

I must have done something like 100 restorations and always look at the channels. I remember seeing what looked like jpeg blocking in the blue chan of one image and of course can't find the image now. I don't recall it causing me a problem.

How common is the issue? Has it become more common recently?

To investigate it would help to have a few examples which could be traced backwards to see when, in the process between capture and appearing in the gallery, the problem occurred.

Athol
Title: Re: JPEG Compression
Post by: Mhayes on February 21, 2014, 02:03:20 AM
Thanks Tori for the links and the perspective.

Athol, I don't think this is becoming more common, but maybe in some of the photos I shot in Lindsborg. What is interesting is that while in NY where the copy run was done with $250,000 copy stands and the photos were shot in RAW and later converted and uploaded as JPG---we had to have one bunch redone because of banding. Back to the jpg blocking issue in the blue channel where on that wedding photo, the red channel gave more detail of the man's head.

Quote
To investigate it would help to have a few examples which could be traced backwards to see when, in the process between capture and appearing in the gallery, the problem occurred.

I see the noose tightening around my neck.  :'(

Margie
Title: Re: JPEG Compression
Post by: jensend on February 21, 2014, 01:28:37 PM
Thanks Tori.

I must have done something like 100 restorations and always look at the channels. I remember seeing what looked like jpeg blocking in the blue chan of one image and of course can't find the image now. I don't recall it causing me a problem.

How common is the issue? Has it become more common recently?

To investigate it would help to have a few examples which could be traced backwards to see when, in the process between capture and appearing in the gallery, the problem occurred.

Athol
I'm the one who brought up the JPG issue recently. It turned out that the camera was set to the minimum size and quality settings. The image was scaled up by 200%, cropped, rotated, color corrected and saved as a JPG again. So the JPG compression was some of the issue, but I think the upscaling was the biggest issue. Hopefully the problems were just with that batch of photos.

The biggest reasons I shoot RAW are the abilility to adjust white balance in post, and slightly higher dynamic range. Neither of these are issues when taking pictures of physical photographs. A JPG workflow is OK in this case, as long as the maximum JPG quality is used before the image gets to the restorer.
Title: Re: JPEG Compression
Post by: Mhayes on February 21, 2014, 02:15:34 PM
Yes, I am the guilty party and although I would like to plead ignorance since this was a rented camera---it really is no excuse.  :knuppel: :knuppel: :knuppel:  :'(  I thought that I was shooting JPG Fine, but I also know that I may have picked the normal setting in trying to not have large file sizes. It really wasn't necessary as we had a very small turnout in Lindsborg.

Quote
I'm the one who brought up the JPG issue recently. It turned out that the camera was set to the minimum size and quality settings. The image was scaled up by 200%, cropped, rotated, color corrected and saved as a JPG again. So the JPG compression was some of the issue, but I think the upscaling was the biggest issue. Hopefully the problems were just with that batch of photos.

At first I had a hard time trying to figure out what you meant by scaling up to 200% and then cropping. My file was 38.667 in (2784 pixels) x 25.778 in (1856 pixels) at 72 dpi. Each photo would have the photo on the copy board and I would straighten the photo and then cropped to the desired dimension that was 8 x 10 at 300 dpi. I didn't understand why you were saying I up-sized it to 200% and then cropped. I didn't, but I guess you are saying that is what it amounted to?

I have learned a valuable lesson here and won't make that mistake again.

Margie
Title: Re: JPEG Compression
Post by: jensend on February 21, 2014, 11:38:57 PM
At first I had a hard time trying to figure out what you meant by scaling up to 200% and then cropping. My file was 38.667 in (2784 pixels) x 25.778 in (1856 pixels) at 72 dpi. Each photo would have the photo on the copy board and I would straighten the photo and then cropped to the desired dimension that was 8 x 10 at 300 dpi. I didn't understand why you were saying I up-sized it to 200% and then cropped. I didn't, but I guess you are saying that is what it amounted to?
The crop tool can crop, rotate and scale all in one step. Any of those steps can also be done individually. If you set a size and DPI for the crop tool, it will automatically scale the image as needed. The final file was 3000 x 2400 pixels, which is bigger than the 2784 x 1856 pixels of the initial capture (and the photo only took up about 1500 x 1200 pixels)