Loss of sharpness

[Sylvie_h]

I use the Canon processing software. I shoot in RAW only and convert and save on a JPEG when processed. However, when I copy my JPEG images on a stick to transfer them to another computer, the sharpness is lost. I don’t know if this is something that can be remedied. Does anybody know why that is?
Sylvie

[MikeOxon]

This seems very strange. How do you copy the files? If the copied file is the same size as the original, I cannot understand how sharpness could be lost - unless the computer you transfer to has a low resolution screen.

[Padfield]

Saving to a lossy file like a jpeg inevitably results in some reduction in sharpness. This will not necessarily be apparent until the file is closed and re-opened without reference to the original, uncompressed file - i.e., in other software or on a different machine. Once saved, the file should not change in any way on being copied or transferred to another machine.

What happens when you save to jpeg, close the file and re-open the saved jpeg on the same machine you process the pictures on?

Guy

[Sylvie_h]

Thank you Mike and Guy for your comments.
Here is what I do: I shoot in RAW only, download the pictures on my laptop. I process the RAW picture with the Canon software with some sharpening and if some cropping if needed, and convert and save in a JPEG. When opening the JPEG, I always check the sharpening and add a little bit if I find there is not enough. I then save any changes I made to the JPEG picture and copy and paste it on a stick to transfer onto another computer. It is only when I open the file on another software (other than the Canon processing software) that I can see that there is a loss of sharpness.
I use Windows photo viewer on my other computer to view the pictures but still I don't understand why some sharpness is lost.
I have checked the resolution on my computer screen and it is set on the highest grade so that should not be a problem. I seem to have the same problem with my laptop when I view the pictures outside my Canon Software. This is very frustrating.
Thanks.
Sylvie

[KeithS]

As Guy said, JPEG is inherently "lossy". I tend to save my astrophotos as TIFs to minimise loss of detail - might be worth using that format if you can, though the file sizes are a bit bigger.

[MikeOxon]

Hi Sylvie,

I am always wary of processing photos on my laptop, since the screen is a bit too small to assess the quality of the photos with any accuracy. When I move to my larger (24") desktop screen, they often look poorer than I expected (hoped!).

As Guy said, the JPEG format does lose some detail, so always use the highest quality JPEG setting during any processing. If you need to save space, you can reduce the JPEG quality but only after completing all adjustments to the image.

The whole matter of 'sharpening' is very subjective and an over-sharpened photo looks far worse than one with too little. Always look at edges at 1:1 size on the screen, to make sure they are clean, without the 'ringing' artefacts that appear with too much 'sharpening'.

If the photos are good in the first place, they should need very little additional sharpening, which is really about enhancing edges - it used to be called 'acutance' back in film days, when there were special developers, intended to produce the same 'crisp' effect.

Adjustment of the contrast can have a similar effect and it may be the settings of your different monitors that is affecting the results you are seeing. It might be worth checking the histograms of your photos, to see that there are no gaps at the ends of the histogram, which can indicate insufficient contrast. Also check the brightness/contrast settings on your monitors.

If you re-size the original photos to something smaller, for showing on the web for example, then a little extra 'sharpening' is usually needed, to compensate visually for the loss of detail on down-sizing.

Good luck,
Mike