Image Size, Compression and Resolution

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DPChallenge Forums >> Tips, Tricks, and Q&A >> Image Size, Compression and Resolution

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barryg

Minolta DiMAGE A1

01/15/2004 02:14:36 AM · #1

I am just starting out in digital photography, having just purchased a Minolta Dimage A1. My question is: what are my best setting choices for image size and compression so as to produce the sharpest resolution for pictures to be submitted to challenges, within the constraints of 150 kb maximum file size and 160-640 pixel range? I am not a wiz yet with any photography software. My image quality setting of Standard is the highest compression JPEG format. A small image size setting of 640 x 480 in Standard mode is going to produce a 240 kb file size. I have played with compression in software and found colors get distorted when heavily compressed. What gives? I would like to be able to shoot in the best image quality mode and still be able to format pictures to meet challenge submission requirements. Any help would be appreciated.

jrs915

Canon EOS-300D Rebel

01/15/2004 02:16:25 AM · #2

you should shoot with the highest resolution quality and the fine jpeg compression.

Then use photoshop or another imaging program to adjust the picture down in size so that it will work for the challenge

Phoetica

Olympus C-300Z

01/15/2004 10:46:56 AM · #3

barryg,
If you want your pictures to be in the 160-640 pixel range only, you can set the finest jpg quality, and you are sure to get under 150kb! Which software do you use for compression and how did you do it? Maybe you just did something wrong in the process.

When submitting to challenges, sometimes you will want to crop your image, so you should use the width 800px, 1024px, or what your camera permits. Anyway, I would strongly suggest the same as jrs915: always shoot with the highest resolution. That's the best - sometimes, you will make a photo you will really like, and then you will regret to not have it in better resolution. The reason is, that if you will want to print it, the higher resolution is better.

If you do not have big enough memory card, so it gets filled up quickly, you can compromise and set the lower jpg quality - you will have to experiment a bit. The chances are, you will not see any difference, especially on the monitor screen.

Phoetica
www.phoetica.com - weblog about photographs.

Message edited by author 2004-01-15 10:48:34.

barryg

Minolta DiMAGE A1

01/15/2004 11:38:01 AM · #4

Thanks jrs915 and Phoetica for the response.

I have mainly been shooting in Extra Fine mode at a size of 2560 x 1920; this produces a file 4,920 KB before software clean-up. I am using DiMage Viewer and can resize this image by setting either the width or height dimension, allowing the software to adjust the other dimension appropriately to the same aspect ratio as the original. I can check either a bilinear or bicubic interpolation prior to resizing. Any opinions as to which is preferred?

My DiMage Viewer software can compress before saving a photo file. If JPEG is selected as the file format, the compression rate must be fixed using a slide bar. I have been experimenting with this slide function and saving photo files to see at what compression value I can capture the largest permissable file size for challenges - a value of 20 to 50 typically does it. I am aware that the higher the compression rate, the smaller the file size, BUT the lower the image quality.

I can shoot also in TIFF and RAW modes. RAW is best but I have not been brave enough yet to tackle all the processing issues that I've read about. I've read on another post that TIFF mode is going the way of the dinosaur.

Do most people shoot in RAW format if they can? What do others typically do?

Thanks, Barry

Phoetica

Olympus C-300Z

01/16/2004 11:34:12 AM · #5

Hello Barry,

Regarding the interpolation and resizing, I'm using either Irfanview or Paint Shop Pro software.

Irfanview is for free, and is sufficient for a lot of basic tasks like viewing, resizing, etc. I use "Lanczos filter" for resampling there.
Paint Shop Pro is a shareware alternative for Photoshop, and I use it for more advanced photo editing. For resizing, it has an option "Smart Size", which is supposed to choose the best algorithm.

Regarding TIFF format, the files are really big, since no compression was applied. It's really up to your decision after all. Most people saw none or very little difference between tiff and jpg files, so they shoot jpg.

RAW is like a photo negative, it's the exact picture the camera chip "see". If you shoot jpg, camera will do some processing with the image, like color balancing, sharpening, etc. If you shoot RAW, you can (and have to) do those steps yourself. So pros prefer this option.

Phoetica
www.phoetica.com - weblog about photographs.

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