Author Topic: floating pixels in jpeg (Read 4431 times)

photo123 · « **on:** April 29, 2011, 10:11 »

Hi to all,

I have a problem about floating pixels when saved as JPEG on isolated photos.

I process with adobe camera raw, photoshop and finally convert it to JPEG. But even if i detaily clean all the edges, when saved as jpeg there becomes floating pixels around the edges. (when i push levels all the way right)

How can i avoid this?

lagereek · « **Reply #1 on:** April 29, 2011, 10:18 »

I know, the answer is that you hold the tip of the pixel slightly above the water level, alternative a frogmans-suit.

microstockphoto.co.uk · « **Reply #2 on:** April 29, 2011, 10:21 »

jpeg artifacts are particularly bad on edges, especially when there's an high contrast

basically you can't avoid it, but you can reduce it by saving .jpg at highest quality: not only at the highest level, but also choosing 4:4:4 instead of 4:2:2 subsampling

also, some compressors are better than others in any particular situation, so you may try to save as .tif and then convert to .jpg with another tool

rimglow · « **Reply #3 on:** April 29, 2011, 10:35 »

Take your pen tool and carefully outline the edge of your isolation. You've just created a path. Save the path. Convert the path to a selection. Feather the selection 2 or 3 pixels. Go to Layer>New>Layer via Copy. Now you have a clean edge all the way around the isolation. Create a new white layer under your new isolated layer, and merge.

By the way, go back to your Path and convert it to a Clipping Path. Isolated objects with Clipping Paths are much sought after.

madelaide · « **Reply #4 on:** April 30, 2011, 12:26 »

I have many TIFF files (that's what I work on) with perfect white backgrounds, yet when saved in JPEG, even at the smallest compression, they show some stray pixels. Some are even illustrations, so there is no isolation issue to be fixed.

This has been discussed here many years ago, in a thread exactly about this (I think I even started it). It's just something inevitable in the algorithm and sometimes an inspector will make an issue about this.

BTW, clipping paths will only be useful at the original size, so they are not a solution or circumvent to the problem.

rimglow · « **Reply #5 on:** April 30, 2011, 12:52 »

Clipping paths are useful at all sizes. Some sites strip them out of lower resolutions, (Dreamstime) others don't (iStock). If you download a photo and make a selection from the clipping path, there will be no floating pixels.

madelaide · « **Reply #6 on:** April 30, 2011, 16:30 »

Thanks for the correction. I remember having read here that all sites would remove the clipping path in smaller resolutions, something the in automated process would not be able to retain that informartion.

lthn · « **Reply #7 on:** May 01, 2011, 17:16 »

Quote from: photo123 on April 29, 2011, 10:11

Hi to all,

I have a problem about floating pixels when saved as JPEG on isolated photos.

I process with adobe camera raw, photoshop and finally convert it to JPEG. But even if i detaily clean all the edges, when saved as jpeg there becomes floating pixels around the edges. (when i push levels all the way right)

How can i avoid this?

Don't push the levels al the way... then you can forget the whole thing, it doesn't matter : )

rimglow · « **Reply #8 on:** May 02, 2011, 09:12 »

@lthn:

The reason you push the Levels all the way, is to check for floating pixels that might not be evident at a normal exposure. You don't actually save that level change, just observe.