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asg
February 8th, 2005, 10:29 AM
What is the best way to post a huge image file? I have this 270MB .tif file of a very good aerial photograph of Manhattan taken in 1996. It covers the entire entire island, but I've cropped it down to the area below about 65th street. The detail is amazingly good.

The free image hosting website I use has a file size limit of 250k, this site has a 150k limit.

Any suggestions as to how post it here while keeping the high image quality?

Thanks.

ryan
February 8th, 2005, 10:51 AM
Posting guidelines

7. Do not post images wider that 800 pixels. If the image is wider, post is as a link.

Why don't you crop several areas to show the detail, and maybe post a lower res version of the whole photo? My monitor is set to show more than 800 pixels, but no one sets their monitor to view a file as large as what you are talking about. If you did get it all on the monitor, you wouldn't see any of the detail anyway because monitors "fake" higher resolutions by not displaying all of the pixels. If you have to scroll to view it anyway, why not just post it in sections?

asg
February 8th, 2005, 12:25 PM
I have resized an already cropped version of this file to 800 pixels wide. Let's see how it looks.
http://img.photobucket.com/albums/v651/asg9000/ManhattanAerial_1996_01.jpg

http://img.photobucket.com/albums/v651/asg9000/ManhattanAerial_1996_02.jpg

asg
February 8th, 2005, 12:34 PM
The original file that I have, and would like to post uncropped, has the whole city below 65th St. at, I guess, a similar resolution to the second attachment above. When I view the original image in Photshop at full size, actual pixels, just a dozen or so square blocks fit on the screen at a time. You have to pan around to see the full image, but the detail is great and it is quite fun.

asg
June 17th, 2005, 05:37 PM
Can someone explain the finer points of posting image files, specifically, how pixel width relates to file size relates to resolution?

I've cropped a .tif file down several times, saving at 800 pixels wide. The resultant file sizes inevitably vary, and when I post them online, the images sometimes are quite big and sometimes small.

Thanks.

ZippyTheChimp
June 17th, 2005, 07:30 PM
The following does not apply to print resolution, which is a different matter.

Image resolution has no meaning when displayed on a monitor. Whether you set the resolution at 72 ppi or 300 ppi, the computer will ignore it, and display the image the same way - according to the monitor resolution, which is usually 72 or 96 ppi.

For simplicity, assume your monitor has only one setting - pixel width and height of 1280 and 1024. That means the total number of pixels the monitor has is 1,310,720.

If you have an image with dimensions of 1280 x 1024, it will fit perfectly on the screen. This will be true no matter what the file size (bytes) is or what the resolution is set at. You can see this in Photoshop. If you change the resolution from 72 to some other value, and then change the pixel dimensions back to the original value - the two images will display exactly the same way on the monitor. So forget about PPI.

All 800x600 images will appear the same size on the same monitor, regardless of file size. The problem is that monitors come in all sizes with different resolutions.

Let's say you monitor has a lower resolution of 1280x720. The total number of screen pixels is 921,600. The original image of 1,310,720 has too many pixels to fit on the screen, so it will appear bigger. It will also be less sharp, because the monitor resolution is lower.

File size: It does not affect image dimensions. an 800x600 will be the same size if it is 100K or 500K. What the file size controls is the image quality. Formats like jpeg compress the file according to an algorithm, which loses some of the data. The larger the file size, the less compression in the program, the less data lost, and the better the image quality.