Why do high res files look grainy when I put them online?

[ltilley]

I have very high resolution files....2048x3072, 300 dpi. But when I upload them and put them online, unless they are at 100% size, they look grainy or weird. Is there something I'm doing wrong?

[another view]

Probably the way you're re-sizing them. Can you give us details on how you're doing it, and maybe post an example?

[OldSchool]

My guess is that your editing software does a much better job simplifying the image for display on your lower resolution (than image) monitor. Web browsers do not do this very elegantly. Sharpening your image will exasperate this. My suggestions are to:

(1) Always review your image with your browser before you upload.

(2) If the image looks lousy in your browser, then resize appropriately (800x600??), resharpen, and then post. I typically have two files for each finished image: "hi-res" for prints and "small" for the net.

BR,
Tim

[ltilley]

Thanks for the answers...I'm usually resizing by using the edit transform tool in photoshop and changing the percentages.

Basically, I was making one image file with multiple images (like a collage) so I was copying and pasting image files and then transforming that layer. Would it make a different if I re-sized the actual file before pasting it to the parent file?

I'll give that a try.

[opus]

I just read an article about what some of the improvements are in PSCS2. One of them is that "The new Photoshop's Smart Objects feature lets you scale, rotate, warp, and transform raster and vector objects on layers of a Photoshop image without losing image quality."


So this was apparently a problem before.

[GB1]

Sometimes re-sizing a bitmap image can cause problems, especially if it isn't a multiple of two.

For a simple example, if a 'line' in the photo is at an angle then the number of pixels to represent this might be something like "5 across, 1 down, 2 across" etc. If you now shrink the bitmap by 25 percent, how would this line now be drawn? It would inevitably be different than the original, because it cannot be directly scaled down.

Note that this example shows that even scaling by factors of two can cause distortion of the original image, but you will have greater chance of this if you choose unusual scaling ratios.

No idea how PS' (new?) algorithm attempts to compensate for this, but you can see that it's a fundamental problem that is best avoided altogether. Try to scan it at the final size you desire, if you really want great results.

-GB