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Question On Compression  
User currently offlineWakeTurbulence From United States of America, joined Apr 2004, 1294 posts, RR: 17
Posted (8 years 5 months 3 weeks 4 days 2 hours ago) and read 2671 times:

I recently had 2 shots rejected for compression only. My question is how can a file that is 1100-1200 pixels wide and less than 1MB, saved at 12 (Maximum) in Photoshop be compressed? Also, how can you tell if a shot is compressed, does the overall quality go down? Another thought I had was that this was with a new lens. I don't think it has anything to do with this matter, but it is a thought. Just curious on what some people think. Thanks.
-Matt


Jetwash Images - Feel the Heat!!!
7 replies: All unread, jump to last
 
User currently offlineJeffM From United States of America, joined May 2005, 3266 posts, RR: 52
Reply 1, posted (8 years 5 months 3 weeks 4 days ago) and read 2643 times:

Quoting WakeTurbulence (Thread starter):
how can a file that is 1100-1200 pixels wide and less than 1MB, saved at 12 (Maximum) in Photoshop be compressed?

If work was done and saved as .jpg repeatedly, you will have compression each time it is saved. Also images with lots of color and detail will be larger after compression.

Quoting WakeTurbulence (Thread starter):
how can you tell if a shot is compressed,

Overly compressed images will have funny artifacts around the edges of certain colors and things within the image.

Quoting WakeTurbulence (Thread starter):
Another thought I had was that this was with a new lens. I don't think it has anything to do with this matter, but it is a thought.

LOL....it has nothing to do with your lens, but it did make me laugh.....


User currently offlineWakeTurbulence From United States of America, joined Apr 2004, 1294 posts, RR: 17
Reply 2, posted (8 years 5 months 3 weeks 3 days 22 hours ago) and read 2628 times:

Glad to get smiles out of you Jeff. When I edit my images I don't save more than once. If I see a problem after saving I will go back and re-edit. Thanks for the tips though. I'll have to go back to the edits and take a closer look to see what's up. Thanks again.
-Matt



Jetwash Images - Feel the Heat!!!
User currently offlineNewark777 From United States of America, joined Dec 2004, 9348 posts, RR: 30
Reply 3, posted (8 years 5 months 3 weeks 3 days 22 hours ago) and read 2623 times:

Make sure your camera isn't set to compress the pictures after they are taken.

Harry



Why grab a Heine when you can grab a Busch?
User currently offlineStealthZ From Australia, joined Feb 2005, 5678 posts, RR: 45
Reply 4, posted (8 years 5 months 3 weeks 3 days 21 hours ago) and read 2619 times:
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Matt,

An uncompressed 8 bit TIFF file of 1200x800 is 2.75Mb so any JPG file of less than a Mb has significant compression.
Do you shoot RAW? If you are shooting JPG there is already significant compression applied. eg a JPG out of my Canon 10D of a typical aviation scene may be 1.5-2.5Mb that same shot uncompresses to an 18Mb TIFF file.

So careful management of compression and image versions is required to minimise degradation.

Cheers

Chris



If your camera sends text messages, that could explain why your photos are rubbish!
User currently offlineWakeTurbulence From United States of America, joined Apr 2004, 1294 posts, RR: 17
Reply 5, posted (8 years 5 months 3 weeks 3 days 21 hours ago) and read 2614 times:

First to Harry, I am pretty sure my camera isn't compressing the files any differently than it has been the last year or so, good thought though. Next to Chris, sorry for the confusion, I was talking about edited files. My original JPG's are between 1.5Mb and 3.5Mb. I shoot JPG for convenience, but I probably should learn about RAW. After 250+ photos on Anet with JPEG I don't see myself switching anytime soon, but it might be good to experiment with and see. Thanks for the thoughts guys.
-Matt



Jetwash Images - Feel the Heat!!!
User currently offlineMartin21 From Netherlands, joined Aug 2001, 347 posts, RR: 1
Reply 6, posted (8 years 5 months 3 weeks 3 days 16 hours ago) and read 2600 times:

Quoting JeffM (Reply 1):
If work was done and saved as .jpg repeatedly, you will have compression each time it is saved.

This is not entirely true. This only happens when opening, saving and closing the photo and opening, saving, closing and so on. When you open a JPG photo you can edit and save it as many times as you want without losing quality. I know for sure, just tested it with photoshop.

Martin21



At 30.000 feet, the sun always shines !
User currently offlineIL76 From Netherlands, joined Jan 2004, 2237 posts, RR: 49
Reply 7, posted (8 years 5 months 3 weeks 3 days 15 hours ago) and read 2592 times:

Sometimes 'strange' sharpening methods/procedures can create the same effect that compression gives. Often the combination of blurring and sharpening (in whichever order) creates that effect too.

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