A oversharpening issue - DPChallenge Forums

Canon EF 70-200mm f/2.8L USM

06/23/2005 06:23:07 AM · #1

I've shoot a wedding and after a few weeks ago. Before that I asked and investigated about what in camera parameters should I use, and has adviced by many people I used all parameters in default values (0), so I could do the editing afterwards. And I did it that way.

Almout all my editing was a bit of levels, an increase of 10� of the saturation and unsharp mask (0.9 pixels, 250% amount and 25 threshold). The images seemed fine in the monitor, and when I pick them at Fuji lab I saw some artifacts that seemed to me has oversharpening artifacts. Some edges of feafs for example in the background almout seem to be draw. I'll post the images later, but in most images the sharpening wasen't noticeable even at 100% pixel view.

I can't find an explanation for it though. I did something that I think that I shouldn't have done: whaen croping the images to fit the prints I cropped them at 300 dpi. So in some cases where the opixel wheren't enough the image was interpolated to get them. Some people said to me earlier about this issue that I should put the measures that I want to crop but leave the dpi box empty so it uses the aspect ratio withought resampling the images. Can this be the reason for it?

Any thoughts?

PaulMdx

Canon EOS-1D

06/23/2005 06:31:07 AM · #2

From my experience labs tend to sharpen images somewhat during the printing process. As such I always tend to sharpen images a little less than I would do for screen use (or printing myself).

Bear_Music

Samsung Galaxy S21, S21+, S21 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

06/23/2005 06:47:50 AM · #3

If you get yourself an "ordinary", hundred dollar color inkjet printer that advertises photographic-quality images, you can (and should) proof your work yourself to intercept these issues before they get to the lab. Use photo-quality paper, and see for yourself. Printers, in general, are MUCH sharper than computer screens, so they don't need anywhere near the USM work that we are accustomed to here. It's one of the real problems of DPC, in a way (not to get sidetracked LOL); that the standard of sharpness demanded by the voters is unrealistic, and requires a completely different PP workflow to prepare a perfectly printable image for DPC competitions. Ditto, incidentally, for "noise", which often (but not always) renders itself as a pleasing subliminal texture in an actual print.

Robt.

06/23/2005 08:47:15 AM · #4

I was very surprised with this result. And it was more notory in the 15x20cm prints. The 20x30cm it was fine. Very sharp ans accurate.

That's why I thought that the interpolation prcess could enhance the effect of sharpning. The 20x30cm was the 3000x2000 original pixels, just done levels and saturation bost.

Canon EF 70-200mm f/2.8L IS USM

06/23/2005 05:40:58 PM · #5

I did the cropping with resampling to 300dpi because I was told at the lab that the machine always printed 300dpi and they gess it interpolated to get those. So I gess I better do it myself to control the process. But the girl at the lab didn't look like an expert. Any other opinions about it?

timj351

Sony DSC-F707

06/23/2005 06:01:39 PM · #6

One thing that stood out to me in your post was the 25 threshold value in the Unsharp Mask. This seems excessive to me and could be part of the reason for the look you are seeing in your prints. Generally the Threshold value is used to minimize some noise in images but it needs to be used carefully and only if necessary. I would suggest keeping the threshold value between 0 and 5, the Radius between .4 and 1, and the Amount to whatever looks appropriate, maybe between 50 and 150. I usually toggle the Preview checkbox on and off to see the before and after results on my screen at 100%. Then view your image again at 50% and 25% to see if it looks right. It's better to error on the side of softness when you are printing photos from a lab, especialy with portrait shots. Softer images are always more exceptable and look more natural than oversharpened shots. I hope this helps and you can make the best of your situation. Maybe just the very best shots can be reprinted if necessary.

T

aboutimage

Canon EOS-30D

06/23/2005 06:07:22 PM · #7

Definately agree with the last post about "unsharp mask" values. My experience has shown the default values for radius and threshold values are best. Just slide the top slider around for effect.