Do you smooth/sharpen photos after scaling for putting on the web?

[Dazz1]

I know that sharpening is best done as the very last step. Should it only be done AFTER the final sizing. This means keeping a master image that's unsharpened, then when you export the image for a target medium, and scale it down as you do for the web for example, sharpen the final scaled image only.

OTOH, do effects like smoothing and sharpening work best when they have the maximum pixels to work on - which would indicate that it's best to do ALL processing before scaling down. But I have read that scaling an image down to a smaller size has a smoothing effect due to the averaging/interpolation of the pixels. Does that mean that SOME images might beneft from a final retouch? maybe a slight sharpening if the smoothing is too much, and/or maybe a slight smoothing in some areas if artifacts from the scaling are present?

[ameerat42]

At 1st glance, my thoughts were a couple of yeses and a couple of nos.
(Call it a bob each way, and ask an emu!)
Sharpening is a sort of contrast enhancement over a very short part of the image.

You say a master image, but that master image would have to be relatively untouched. Then, if you wanted a large size version,
sharpen the master and then "save as" another filename, so that you still retain the master as you opened it(!!)

If you want a smaller version, re-size the master and do another "save as" with a different name, then see what the smaller version
need in terms of sharpening/smoothing.

The ALL processing would be what you did to the master image only, so I suppose that's one of the nos above.

So, that's why I said yes/no x 2.

But it sounds like you're figuring some of this out yourself - which is good. Sometimes you have to read carefully into replies to
determine whether anything said is always, or only sometimes, the case.
Am.

[Dazz1]

At 1st glance, my thoughts were a couple of yeses and a couple of nos.
(Call it a bob each way, and ask an emu!)
Am.

:lol: Love that expression. Can I use it?


Yes, what you are describing, re: master image, and save as after scaling, then see what needs tweaking, is what I am starting to do. Now if I can just learn to use a lighter touch when sharpening... and certainly using an edge mask makes that a lot better...

[WhoDo]

Now if I can just learn to use a lighter touch when sharpening... and certainly using an edge mask makes that a lot better...

You could also look at high pass filter sharpening, wet. That's another method that can give excellent results with little or no blowback in the form of haloing. Worth a look.

[Dazz1]

You could also look at high pass filter sharpening, wet. That's another method that can give excellent results with little or no blowback in the form of haloing. Worth a look.

Certainly is - I ran across it in one of the tutorials here earlier today - although I am vague on the difference, as I sort of thought edge detection was a type of high pass filter as well.

[ameerat42]

Does GIMP do it?
(You use GIMP, don't you?)

[Dazz1]

Does GIMP do it?
(You use GIMP, don't you?)

Yes, and yes. Even has scripts to automate it. Seems to work well.

- - - Updated - - -

I just tried out a new high-pass filter sharpen and the results seem good to me. See what you think.


Before...
http://ubuntuone.com/4SJZketrY0ENAZ2G5YdBPs
After...
http://ubuntuone.com/17upylPPoqws1ie1JA8AXa

[WhoDo]

The difference between Edge Mask and High Pass Filter sharpening, explained by DigitalPhotoPro:

Edge sharpening adds a mask that targets the contours of an image, allowing more aggressive sharpening with fewer side effects. Like Edge sharpening, High Pass sharpening (named for the filter used to produce the effect) targets contours in an image, but it does so without the need for a mask. Unlike Edge sharpening, the contour accentuation it produces is soft, feathered and wide. The effect is substantially different and can be used for many creative effects. High Pass sharpening is very similar to the effects of ACR and Lightroom's Clarity slider, but it offers more control and more varied effects.

I hope that explains the difference. The way I read it high pass sharpening depends less on the contrast at the immediate edges and doesn't require a mask.

Your results above indicated what a brilliant tool it is, too. :th3:

[ameerat42]

AAGGHHH! Yes, they're not bad. I can NEVER get these all sharp.

[arthurking83]

Two comments I'd like to make:

1. try to use sharpening selectively. No matter what sharpening routine you use, but there's no point in sharpening obviously blurry sections of the image, and in fact there is harm to be done.
(note how a blurred background becomes more grainy if you sharpen it)

2. if you have plans to keep an original version of the file(which you should), what I would do in your situation would be: create a copy of the original jpg file. (call it something obvious like <insert camera file name>_copy.jpg)
Work on this copy. Don't touch the original. Remember part of the problem with the jpg file type is that they lose some quality with every edit->save routine... so you want to minimise this situation.

With the large copy version of the jpg, do all your edits as you prefer but no sharpening and then save as a smaller jpg file for uploading to the net. Doing a save as with a different file name and file size, will leave your large size copy untouched(so less destructiveness is going to affect it). If you feel you need to save this large copy too, then by all means save it if you have too. Then, once the smaller file is uploaded to wherever you upload too .. delete it.

But you should try to keep your jpg file from the camera unedited and as your archive image. Even tho it's not edited and may not look as good as your duplicated, edited large file .. almost guaranteed that at some point in the future, your post processing skils will improve, your software will improve, and you may come back to some of your earliest images to redo them again. Editing an image ..... that you thought looked better(now) but may be not as good as you thought it was with the benefit of hindsight ... may be a bit more difficult.

With jpgs, try to minimise the number of sharpening routines you do to the file.


So, with this, you will always have 1 version of the camera file: (possibly) 1 version of the edited large copy of the camera file: and 1 version of the smaller scaled down for web use jpg file.
I wouldn't hesitate to delete the large edited copy and the scaled down version after a short time .. say 6 months or a year later .. but, I'd also keep not only the original jpg, but a copy of the original jpg file on another location. The offshoot files can easily be replicated, but the original jpg can never be replicated once edited.

[Dazz1]

But you should try to keep your jpg file from the camera unedited and as your archive image. Even tho it's not edited and may not look as good as your duplicated, edited large file .. almost guaranteed that at some point in the future, your post processing skils will improve, your software will improve, and you may come back to some of your earliest images to redo them again. Editing an image ..... that you thought looked better(now) but may be not as good as you thought it was with the benefit of hindsight ... may be a bit more difficult.


Lot's of good advice, thanks.

I have done some selective sharpening. Works well. I discovered a function in Gimp which feathers the edges of a selection, and this helps hide the boundary between the selective edit and the rest. I think selecting just the parts of an image that you want to edit is a bit of an art. It's something I have been practicing.

Also, I am already finding that I can go back to old images and improve previous attempts at PP. Luckily I already had the habit of only editing a copy of the original from the camera. The photo management software I use does this automatically. When I select to edit a photo in the external editor (Gimp) it copies the original, to a new name - appending '_modified' to the original name, and handing that to Gimp for editing instead of the original. I also run backups daily, which include all my 'Picture' folder, to an external drive. All the new photos are filling that drive up, but replacement drives are cheap for terabytes of storage, so that's what I will do.