Compression Problems - DPChallenge Forums

Pentax DA 18-55mm f/3.5-5.6 AF

05/13/2004 09:29:16 PM · #1

I'm tending to get images that are over-compressed when submitting to challenges. Is there an easy way to fix this?

faidoi

Pentax K10D

05/13/2004 09:30:55 PM · #2

Examples. What is your workflow?

05/13/2004 09:30:58 PM · #3

I usually use save for web in photoshop. Other imaging software usually has something similar.

What steps do you take to get the image down to size?

05/13/2004 09:31:36 PM · #4

I just resize 100 pixels at a time from say 2000 to 640.

05/13/2004 09:33:05 PM · #5

This gets you to the right dimensions. What quality do you use when saving the file?

05/13/2004 09:36:06 PM · #6

I use PSP and I just save it as a JPEG if its a RAW or JPEG coming out of my camera.

05/13/2004 09:38:40 PM · #7

When you work on a photo do you work on a copy? (probably) Is the copy in a lossless format (Tif). Jpeg is lossy. Every time you open a jpeg and change something then resave it it is recompressed. The image eventually turns to mush.

05/13/2004 09:44:37 PM · #8

I work with the original and save it is a copy after resizing it...

Message edited by author 2004-05-13 21:47:34.

05/13/2004 09:47:59 PM · #9

Originally posted by Tranquil:

I work with the original and save it is a copy after resizing it...are tif's bigger (in file size) than jpegs?

tifs are bigger however you don't lose detail when you save. PSP may have an associated lossless format that takes up less space than a tif (I don't know). You should only save as jpeg once you're done editing the image.

05/13/2004 09:50:55 PM · #10

Originally posted by cpanaioti:

You should only save as jpeg once you're done editing the image.

That's what I do...take a look at the compression problems on my abstract shot.

05/13/2004 09:55:44 PM · #11

I'm not seeing any jpeg artifacts in your abstract image. Maybe what you're calling a compression problem is actually something else, or my definition is different than yours. Is it the banding in some of the colours that you are referring to?

For an example of jpeg artifacts, look at my image here: (look closely at the sky)
//s94444053.onlinehome.us/galleries/travel/maritimes/picture_pages/FrenchRiver.jpg

Pentax DA 18-55mm f/3.5-5.6 AF

05/13/2004 09:57:50 PM · #12

I guess that shot was not the best example (mine) but what I am getting is bands and noise around the sharper amd finer edges of my composition (although no extra sharpening was added)...any help would be appreciated but i need to leave for now...thanks

faidoi

Pentax K10D

05/13/2004 10:02:32 PM · #13

Originally posted by Tranquil:

Are you using in camera sharpening? I've read some threads that say that when using in camera sharpening and post processing it afterwards sometimes causes this.

Olyuzi

Panasonic Lumix DMC-GX7

Panasonic Lumix G 14mm F2.5 ASPH

05/13/2004 10:11:01 PM · #14

I took a look at your abstract shot and I do see artifacts that look like they come from jpeg compression problems. It also looks to me like you may have some bleeding of colors into adjacent areas...also jpeg problem. One more thing I see is that it looks like you either have some pixelation problems or stair-stepping.

My first question to you is how much you enlarged this photo to get it to the size is it now? Secondly, it may be that you don't have enough light in the scene too. What size did you originally shoot it in?