Maximum Picture Widths in Forums

Lee · 4th December 2004, 01:39 PM

The process of reducing the file size of an image may either 1. encode patterns and blocks of the same color, like a zip file or digital shorthand, for a smaller file which then requires processor time to re-expand. 2. throw away all of the data that is not going to be missed at the intended display resolution, such as in 'lossy' formats such as jpeg. This is why, when you try to zoom in on most web images you have stored on your disk, there is only useless empty magnification.

I am not familiar with the programs mentioned above, and I am pretty much spoiled by PhotoShop. When I am putting an image on the web, the first thing I will do is crop out extraneous periphery, next I will fix contarast and color balance, then I will resize the image to 640 wide. This blurs the image somewhat as the new pixel grid is unlikely to perfectly overlap the original. I then employ the 'unsharp mask' to artificially restore an appearance of clarity. PhotoShop then presents me with a side by side view of the original image and a proposed jpeg compression. I then visually alter the quality (compression) setting for the smallest file size still carrying adequate clarity. I have the entire process scripted, so it will take only 15 or so seconds if the original image is of good quality.

I believe many of the photo upload and hosting sites probably automate the compression process and I understand that there is even a free add-on in the vbulletin user community which will accept oversize pictures and then reduce and compress them to fit the limits. Perhaps I need to investigate that, though I hate to do anything which would further bog down the speed of the server.

Ian · 5th December 2004, 02:48 AM

... but the learning curve can be steep for those who are not very familiar with manipulating digital images.

What Lee has described is a very good way to achieve a small file suitable for displaying on a screen. There are other techniques for sharpening images in Photoshop, including the "Sharpen" and "Sharpen Edges" filters. In all instances where you wish to sharpen the image, the sharpening effects must be applied after resizing the image or adjusting the numbers of pixels per inch. Basically, sharpening effects alter the pixels at boundaries between colors, increasing the contrast and creating an illusion of a sharper image. If you happen to resize the image (or change the pixel count per inch) after applying these effects, the resulting rearrangment of color pixels will degrade the "sharpened" effect.

The sharper the image, the more the image can be compressed without losing clarity. Of course, the sharpening effects need to be balanced asthetically with the changes in contrast and color that occur from applying these effects. There can still be a lot of trial and error ("art") in manipulating simple digital images.

Images produced for screen displays usually are created with resolutions of 72-90 pixels per inch. Most monitors cannot handle higher resolutions, so it is a waste of file space to use higher pixel counts.

Images produced for screen displays are not usually very good for printing because of their low resolution. Most laser printers these days can print 600+ pixels per inch. Good quality digital prints usually need at least 600 pixels per inch, and often higher for first class work. The higher resolution of these images makes for really big files.

One last suggestion. Whenever I am working on a digital image, I always work on a copy of the original. It is sometimes very difficult to undo an applied effect and recover the original image.

Ian.

Andrew · 5th December 2004, 03:59 AM

Thank you very much, Gentlemen. Great information!

Lee · 5th December 2004, 03:23 PM

Here is a picture of a well worn takouba hilt:

The original image was 12 mb. The reduction above is just under 50 kb. About as much detail as a computer screen can display at intended size, but no more. I could zoom into the original as if I had a magnifying glass in my hand - but not this one.

Looking at the poll above, I suspect we are heading to a new standard of 800 wide instead of 640. When I started this project in the age of dialup and most people running 640x480 screens, the design standard was 480 maximum width.

Remember , if you do not have a good photo editor or time to learn to use it, you may still e-mail pictures to me. I will process them and mail the optimized images back to you.

View Poll Results: Which is the widest arrow that fits comfortably on your screen?
1024 pixels	7	21.21%
800 pixels	22	66.67%
640 pixels	4	12.12%
All are too large	0	0%
Voters: 33. You may not vote on this poll

4th December 2004, 01:39 PM	#1
Lee EAAF Staff Join Date: Nov 2004 Location: Upstate New York, USA Posts: 937	Photo Compression in an Overcompressed Nutshell The process of reducing the file size of an image may either 1. encode patterns and blocks of the same color, like a zip file or digital shorthand, for a smaller file which then requires processor time to re-expand. 2. throw away all of the data that is not going to be missed at the intended display resolution, such as in 'lossy' formats such as jpeg. This is why, when you try to zoom in on most web images you have stored on your disk, there is only useless empty magnification. I am not familiar with the programs mentioned above, and I am pretty much spoiled by PhotoShop. When I am putting an image on the web, the first thing I will do is crop out extraneous periphery, next I will fix contarast and color balance, then I will resize the image to 640 wide. This blurs the image somewhat as the new pixel grid is unlikely to perfectly overlap the original. I then employ the 'unsharp mask' to artificially restore an appearance of clarity. PhotoShop then presents me with a side by side view of the original image and a proposed jpeg compression. I then visually alter the quality (compression) setting for the smallest file size still carrying adequate clarity. I have the entire process scripted, so it will take only 15 or so seconds if the original image is of good quality. I believe many of the photo upload and hosting sites probably automate the compression process and I understand that there is even a free add-on in the vbulletin user community which will accept oversize pictures and then reduce and compress them to fit the limits. Perhaps I need to investigate that, though I hate to do anything which would further bog down the speed of the server.

5th December 2004, 02:48 AM	#2
Ian Vikingsword Staff Join Date: Dec 2004 Location: The Aussie Bush Posts: 4,397	Photoshop is tops ... but the learning curve can be steep for those who are not very familiar with manipulating digital images. What Lee has described is a very good way to achieve a small file suitable for displaying on a screen. There are other techniques for sharpening images in Photoshop, including the "Sharpen" and "Sharpen Edges" filters. In all instances where you wish to sharpen the image, the sharpening effects must be applied after resizing the image or adjusting the numbers of pixels per inch. Basically, sharpening effects alter the pixels at boundaries between colors, increasing the contrast and creating an illusion of a sharper image. If you happen to resize the image (or change the pixel count per inch) after applying these effects, the resulting rearrangment of color pixels will degrade the "sharpened" effect. The sharper the image, the more the image can be compressed without losing clarity. Of course, the sharpening effects need to be balanced asthetically with the changes in contrast and color that occur from applying these effects. There can still be a lot of trial and error ("art") in manipulating simple digital images. Images produced for screen displays usually are created with resolutions of 72-90 pixels per inch. Most monitors cannot handle higher resolutions, so it is a waste of file space to use higher pixel counts. Images produced for screen displays are not usually very good for printing because of their low resolution. Most laser printers these days can print 600+ pixels per inch. Good quality digital prints usually need at least 600 pixels per inch, and often higher for first class work. The higher resolution of these images makes for really big files. One last suggestion. Whenever I am working on a digital image, I always work on a copy of the original. It is sometimes very difficult to undo an applied effect and recover the original image. Ian.

5th December 2004, 03:23 PM	#4
Lee EAAF Staff Join Date: Nov 2004 Location: Upstate New York, USA Posts: 937	An example of a 800 pixel wide optimized jpge image Here is a picture of a well worn takouba hilt: The original image was 12 mb. The reduction above is just under 50 kb. About as much detail as a computer screen can display at intended size, but no more. I could zoom into the original as if I had a magnifying glass in my hand - but not this one. Looking at the poll above, I suspect we are heading to a new standard of 800 wide instead of 640. When I started this project in the age of dialup and most people running 640x480 screens, the design standard was 480 maximum width. Remember , if you do not have a good photo editor or time to learn to use it, you may still e-mail pictures to me. I will process them and mail the optimized images back to you.

5th December 2004, 03:59 AM	#3
Andrew Member Join Date: Nov 2004 Location: USA Posts: 1,725	Thank you very much, Gentlemen. Great information!