Digital Math - sizing images

[KenEng]

Is there anyone out there that could explain sizing images on ACDSee?

I was trying to batch size 2Mb .jpg files to 1Mb files by using percentages. I asked it to reduce the image by 50% figuring that would get me to 1Mb... Nope, got me down to a 75Mb file. After toying around I settled on a 500Mb at 99% of the original image. 99% of 2Mb is 500Mb??? Very screwy.

Ken

[HoonIm]

Hi Ken,

I notice no one responded to your question here. I don't use ACDSee so I'm not sure if I can answer your question exactly. However, I'd venture to guess that what you're thinking of a "size" and what the program is means by "size" are different. ACDSee probably means size in pixels ... so 1200x800 pixel image would be reduced to 600x400 pixel image. That's 25% of the original image but 50% on each side.

But you want the file size to be 50% ... which is actually pretty hard to do. The reason why it is hard is due to compression. I'm guessing that you are dealing with JPG images and compression will determine the size of the file.

For most people, the image size (number of pixels) is more important than the file size. But if the file size is more important to you and you want to get exactly 1MB files, then I'd say you're pretty much out of luck.

Hope this helps.

[otto]

Ken check out this excellent freeware program. You can resize and batch convert to any percentage in a snap. It makes more sense to resize to a standard screen size usually though. I don¥t think you can find a program that has an algorithm that will calculate bytes, because the color content is so different.

[ January 24, 2003: Message edited by: otto ]

[Chad_Naujoks]

You can also use Adobe PS to optimize for a file size. (that is changing the compression of the file to get exactly what size file you want)

Chad

[Jerry_Sutherlin]

I too am for an advanced text on the math of digital photos. Here is a tech note from "ask an expert at ACD See. If nikon improves it "nikon view" program I would get the 3.5. because ADCSee does not seem able to get the plug in from Nikon to handle NEF files. If they do I would stay with nikon. Let me know if you find text. Thanks Jerry



Translating MegaPixels to Print Resolution
Robert Cooper
07-21-01

Q. What size prints can I get from different megapixel cameras? A. To figure out what size prints you can make from today's digital cameras, you have to first break down the pixel measurements. For example, a 3.34 megapixel camera works out to dimensions of approximately 1536 x 2048 pixels, while a 2.24 megapixel camera works out to approximately 1280 x 1600 pixels. For a reasonable quality print you need approximately 150 pixels per inch of resolution (we'll call this medium quality), while for professional quality prints you need at least double that. For simplicity's sake, pick either the long or short dimension of the print/camera resolution and work with that one. For this instance we'll use the long edge of the print. Let's work through a couple of examples: Maximum print size (medium quality) for a 2.24 megapixel camera: 1600 divided by 150 = 10.7." Using this example, you could get a medium quality print of up to about 10 inches (so you could get a medium quality 8"x10") Maximum pro quality print size would be 1600 divided by 300 = 5.3". In this case, you'd be able to get a pro quality print at 3.5" x 5". Maximum print size (medium quality) for a 3.34 megapixel camera: 2048 divided by 150 = 13.65", so you'd be able to get a medium quality print of close to 11" x 14". Maximum pro quality print size would be 2048 divided by 300 = 6.8." In this case, you'd be able to get a pro quality print at 5" x 7." Keep in mind that these guidelines are not absolute! Your lens, lighting, CCD quality and method of printing all play a huge part in the final results. Also, the resolutions quoted are based on optical resolution and not interpolated (upsampled) resolution. The formulas can be applied to cameras of any resolution, or you can work the formula backwards to find out how many megapixels are required to get the image quality you require at the size you will be printing. Good luck!