Color Depth and Resolution

[bobt]

Using 32bit vs. 24bit or 16bit color have anything to do with a picture's image quality, as far as resolution or clarity of an image is concerned? Can you really tell the difference between an image saved in 16bit color vs. one saved in 24bit or 32bit? I personally think that color depth has nothing to do with the resolution or sharpness of an image but would like some feedback from the pros. But the quality or appearence of an image saved using these different color depths [16bit, 24bit or 32bit] might be a different matter. Can anyone really tell the difference between a 16bit image and a 32bit image?

[John Stutz]

16-bit is absolutely too limited. Don't even think about it.

32-bit color is actually 24-bit color but with 8 additional bits of an alpha channel. Usually, this alpha channel is blank. The convenience of 32-bits simply has to do with byte alignment since computers naturally process data values in chuncks of 32-bits. Your software may get some speed performance, but the image should be exactly the same.

Some higher end software packages may store additional data in the alpha channel, but I couldn't tell you what type of data. Consider it an inconsequential file format issue. If your application natively uses a 32-bit format, then let it, and try not to lose any sleep over the extra space.

Even if you had an application that could use 32 bits of color, it is unlikely that any of the other real-world devices (monitor, printer) that you viewing these images on could make use of these extra bits, so they'd be converted back to 24 bits.

[bobt]

Thanks a lot John. So the human eye can't really tell the difference between 24bit and 32bit. One other question I forgot to ask is refresh rates on monito screens. The higher the refresh rate the better the image or does it really make a lot of dfference?

[John Stutz]

The crux of my last post was that 32-bit file formats are really 24-bit color images, with 8 empty bits of nothing. So in essence, they would each contain exactly the same color information. No more or less.

The human eye (reportedly) can distinguish up to 10 bits per color. 24-bits encodes only 8 bits per color. So, hypothetically, if a 32-bit image were to store 10 bits per color (30 bits + 2 wasted bits) then it could hold more detail. However, since they still only store 8 bits per color (24 bits + 8 wasted bits), it's not an issue.

As for refresh rates, it only matters if it's too low, in which case you'll see flicker and looking at the screen will annoy you. Once you exceed a certain minimum refresh rate, the image will apear crisp and you're good to go. Anything above that should make no difference.

[bobt]

How do png and tiff files differ from from the coventional gif and jpeg files?

[John Stutz]

PNG and GIF are similar, both are best for graphics rather than images. PNG is not protected by a patent. Neither will lose data.

JPG is best for images, but the compression method is lossy. You can control how lossy. But the more quality you preserve, the larger the file will be.

TIFF is a general purpose file format, typically used to store uncompressed image files in the most excruciatingly bloated way possible, bound only by the laws of physics.

[bobt]

When I save jpeg, gif files in a folder after downloading them from the 'net does it degrade the content of these folders by copying them to another disk partition by using the copy command or "dragging" the folder to another location by using Explorer? Shouldn't they be saved in the tiff format before dragging the folder with image files in it to another location, by using Explorer or by using the copy command, or does it make any difference with jpeg or gif files?

[John Stutz]

Saving images from the web or copying images from one folder to another will not degrade or alter the image in any way, nor other images in the folder.

It's merely a gargantuan waste of time and space to involve TIFF. In fact, if you save to TIFF and then resave to JPG, you will unavoidably degrade the quality of your image.

[bobt]

This last bit of information I did not know. I have saved a lot of images in tiff format thinking that they were protected but I guess that was a waste of space and time. I still have the origionals in jpeg format. I have learned the hard way never to delete any of my origional image files. Thanks John for this last bit of info.

[TomNine]

I thought we resolved some of these questions a few months ago.

http://www.ftppv.com/ftvideo/showthread.php?t=1300

[bobt]

Most of my questions involved color depth, resolution and refresh rates which wasn't covered in my first post but the last part of my last thread concerning image degradation in over-copying images most certainly was covered in my first post, in great depth. Yes Tom you were right about that and I had forgotten about, so I re-visited my first post and re-copied it again and transfered to a floppy....safe from any hard disk crashes. Now let's just hope my floppy doesn't crash. :)