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DPChallenge Forums >> Tips, Tricks, and Q&A >> Resolution vs Quality
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04/06/2004 10:02:25 AM · #26
It would be interesting to also compare them to the bicubic softer and sharper algorithms in photoshop, which Adobe claim remove any need for any step interpolation approaches at all - which seems true from the small samples I've tried it on.
04/06/2004 08:06:56 PM · #27
I assume you mean in CS? If you're interested (and willing), I put the original for this photo here. I tried the other PS7 resampling algorithms (bilinear and nearest neighbor): bilinear created a very soft, blurry result, which was unusable, and nearest neighbor got very jagged after just two steps, so I gave up on it. I didn't get a chance last night to look for a better shot for testing, as far as the haloing.
04/06/2004 08:23:23 PM · #28
I see haloing in the original. In PSP7 (which is all I have), a one-time resize did not have bad haloing, but did have jaggies as your example showed. By stepwise resizing in 10% increments down to the same size, I ended up with a total loss of sharpness - unusable.
04/06/2004 08:37:50 PM · #29
Originally posted by stevens:

I see haloing in the original. In PSP7 (which is all I have), a one-time resize did not have bad haloing, but did have jaggies as your example showed. By stepwise resizing in 10% increments down to the same size, I ended up with a total loss of sharpness - unusable.


Are you sure you're using bicubic? That sounds like the results I got using bilinear. I don't remember which is set as the default when you first install PS.

I just tried resizing that image directly (no steping) using bilinear, and that seems to strike a balance between the two - less jaggies than a direct resize using bicubic, but still noticable; less haloing than stepped resize using bicubic, and maybe as good or better than direct resize using bicubic.
04/06/2004 09:07:59 PM · #30
Here it is:

Bicubic sharper
' . substr('//www.pbase.com/image/27685379/small.jpg', strrpos('//www.pbase.com/image/27685379/small.jpg', '/') + 1) . '

Visually, at 100% I can see a difference in quality between your bicubic sample and the stepped resize sample.

Visually I cannot see a difference between the stepped resize and the bicubic sharper resized version. Prior to getting PS CS, I would do a bicubic resize, then sharpen again - I don't do that now.

There are differences if you zoom in on the stepped resize and bicubic sharper resized versions. To my eye, the bicubic sharper version looks cleaner, particularly around the reeds, but it is difficult to make a judgement which one is better - as the original has quite a lot of halo anyway.
04/06/2004 09:14:26 PM · #31
Scott, is it possible that your camera applied a sharpening algorithm to the image?
I have a mini dv video camera that is all but useless because it applies far too much 'sharpening' internally. Any backlight object exhibits severe halos, both light and dark.
HUMBUG!
04/06/2004 09:26:46 PM · #32
Here's (maybe?) a better sample:

Resized straight (bicubic):
' . substr('//images.dpchallenge.com/images_portfolio/7151/thumb/68696.jpg', strrpos('//images.dpchallenge.com/images_portfolio/7151/thumb/68696.jpg', '/') + 1) . '

Resized straight (bilinear):
' . substr('//images.dpchallenge.com/images_portfolio/7151/thumb/68697.jpg', strrpos('//images.dpchallenge.com/images_portfolio/7151/thumb/68697.jpg', '/') + 1) . '

Step resized (bicubic):
' . substr('//images.dpchallenge.com/images_portfolio/7151/thumb/68698.jpg', strrpos('//images.dpchallenge.com/images_portfolio/7151/thumb/68698.jpg', '/') + 1) . '

The jaggies show up primarily in the ropes. As far as I can see, there's no noticable halo in the original, and I don't see any introduced in the resized versions.

Gordon: I'd say the bicubic sharper one is definitely the best of the bunch. It not only eliminated the jagged edges, but the final result is nicely sharpened (duh) - the lettering on the train, especially to the left, is much clearer. And anything that can be done in one step, intuitively, is always better than a work-around.
04/06/2004 09:33:29 PM · #33
Originally posted by ScottK:

Are you sure you're using bicubic? That sounds like the results I got using bilinear. I don't remember which is set as the default when you first install PS.

I just tried resizing that image directly (no steping) using bilinear, and that seems to strike a balance between the two - less jaggies than a direct resize using bicubic, but still noticable; less haloing than stepped resize using bicubic, and maybe as good or better than direct resize using bicubic.


No, I was using "smart size" whatever that is. I have played around with it more and I agree with what you and Gordon are finding. The bicubic single resize is about the best. Bicubic stepped resizing introduces too much halo as in your original post. Bilinear works at a single resize, but the stepped resizing is too blurry. Thanks for raising the issue. Another day, another lesson learned.
04/06/2004 09:37:46 PM · #34
Originally posted by ScottK:

Here's (maybe?) a better sample:


I tried PS CS's bicubic sharper on your original and it's still the best.

By the way, is your working space adobe rgb?
04/06/2004 11:33:37 PM · #35
Originally posted by dwoolridge:

Originally posted by ScottK:

Here's (maybe?) a better sample:


I tried PS CS's bicubic sharper on your original and it's still the best.


I guess at this point it all has to be qualified by which version you're using. Bicubic sharper looks to be the best of all choices (at least within PS - I haven't even looked at alternatives mentioned outside PS). But if you're working in 7, like I am, I think that stepping generally improves jagged edges, but obviously I need to start paying a little more attention to the results.

Originally posted by dwoolridge:

By the way, is your working space adobe rgb?


Yes. Any suggestions on whether that's good, bad or ugly would be appreciated. :)
04/06/2004 11:35:51 PM · #36
Originally posted by ElGordo:

Scott, is it possible that your camera applied a sharpening algorithm to the image?
I have a mini dv video camera that is all but useless because it applies far too much 'sharpening' internally. Any backlight object exhibits severe halos, both light and dark.
HUMBUG!


Meant to respond earlier....

Yes, the camera definitely had sharpening set to it's default level. The Canon A40, which that shot was taken with, is usually considered to be somewhat soft (not real aggressive with it's in camera sharpening), but in this case, it definitely seemed to over do it.
04/07/2004 12:02:39 AM · #37
The halos were only obvious where the reeds were backlit by the sky. Maybe the high contrast fooled the camera's processing.
My old Dimage 5 has three levels for sharpening, soft, normal, and sharp. (A peculiarity of this camera: it can 'bracket' the contrast, color, or exposure.)
The highest sharpening setting always overdoes the job so I never use it. Rather use the better capability of PS for that purpose.
When I saw your moniker, it looked familiar and I thought you might be Scott Kelby, wellknown PS expert! Close!
04/07/2004 03:26:09 AM · #38
Originally posted by ElGordo:

When I saw your moniker, it looked familiar and I thought you might be Scott Kelby, wellknown PS expert! Close!


Whoa! What a wild coincidence. As I bring up this thread, I have his PS For Digital Photographers book sitting on my lap! (Trying to come to grips with his suggestion to work in the Adobe RGB color space vs. Gordon's suggestion to work in the sRGB space. Wish I understood this better...)

On in camera sharpening, I've taken to using the low sharpening setting on my G5. I'm starting to get a little more comfortable with sharpening, and more importantly, not oversharpening.
04/07/2004 05:14:35 AM · #39
Originally posted by ScottK:

Originally posted by dwoolridge:

Originally posted by ScottK:

Here's (maybe?) a better sample:


I tried PS CS's bicubic sharper on your original and it's still the best.


I guess at this point it all has to be qualified by which version you're using.


I thought it was pretty clear that I'm using PS CS.

Originally posted by ScottK:

Originally posted by dwoolridge:

By the way, is your working space adobe rgb?

Yes. Any suggestions on whether that's good, bad or ugly would be appreciated. :)


Well, I suppose it's good if your monitor is calibrated to D65/2.2 and you're generating high-bit input in that particular space (or a device space converted to it) as you might when converting RAW files. There's no compelling reason to take low-bit input (i.e. sRGB JPEG) and convert to that space.

Just based on your file name, I'm assuming you're shooting JPEG, so converting to Adobe RGB is ill-advised. However, I only bring it up because the images you've uploaded to DPC look like they were saved directly while in the adobe rgb space. That's bad and ugly. You should treat the web/dpc like any target output device/space and do the appropriate conversion before saving your final web version. Again, I'll reiterate that when shooting JPEG, there's reason not to use Adobe RGB and stick to sRGB instead.

Message edited by author 2004-04-07 15:54:17.
04/07/2004 08:18:09 AM · #40
Originally posted by ScottK:

Originally posted by ElGordo:

When I saw your moniker, it looked familiar and I thought you might be Scott Kelby, wellknown PS expert! Close!


Whoa! What a wild coincidence. As I bring up this thread, I have his PS For Digital Photographers book sitting on my lap! (Trying to come to grips with his suggestion to work in the Adobe RGB color space vs. Gordon's suggestion to work in the sRGB space. Wish I understood this better...)



When did I suggest that ? I'm not saying I haven't, but you have to understand the context.

I work in AdobeRGB, until close to the final output stages.
But I also have a colour managed workflow, profiled input devices and a calibrated and profiled monitor.

I've suggested sRGB for people who don't have any of the above and aren't really doing colour managed workflows (it is the best, lowest common denominator workspace to work in, if you are ignoring colour management) If you work in AdobeRGB in that case, you'll get colour shifts and loss of saturation when you output to the web for example.

If you are doing the colour management thing (and that only makes sense once you've calibrated and profiled your monitor, as an absolute minimum, then AdobeRGB may or may not make sense, depending on the specifics of what you are doing)

Kelby's book devotes an entire 2 paragraphs to colour management, and the second one is explaining how to use the settings dialog in photoshop. He mentions AdobeRGB as a great space to work in for print output, which is partially true - but will mess you around if you want good matching on the web.

It doesn't even mention having an even vaguely calibrated monitor for the colour correction section (if you don't know if what you are looking at is correct, how are you using it to correct anything? (unless you do everything by the numbers)) or anything at all about print output or print/ monitor matching. The truth is, there isn't a one size fits all answer to this, though for a typical hybrid workflow, AdobeRGB is a good trade-off between the giant LAB space and the constrained sRGB space, assuming you are aiming to do print and web output.

Not to say it isn't a great book, it just isn't really about this subject. For some context, the Bruce Fraser book on colour management devotes roughly 2 chapters to answering just this one question.

Message edited by author 2004-04-07 09:36:33.
04/07/2004 07:06:29 PM · #41
Originally posted by Gordon:

Originally posted by ScottK:

(Trying to come to grips with his suggestion to work in the Adobe RGB color space vs. Gordon's suggestion to work in the sRGB space. Wish I understood this better...)


When did I suggest that ? I'm not saying I haven't, but you have to understand the context.


Sorry, that definitely was out of context, and not really meant to be relevent to this thread. I had just come off reading this comment you made in this thread:

Originally posted by Gordon:

I'd agree that if you are using adobe gamma and eyeballing the calibration, that you should basically just default to sRGB, set Photoshop to convert to that working profile and just work in that space.


And that after what I'd read from Kelby's book (basically that sRGB is the absolutely worst color space you can work in, just switch without question) just left me scratching my head. I didn't mean it to sound like you were personally giving me bad advice or something, just giving the background for the interesting (I thought) coincidence.

Anyway, that's lots more good info for me to chew on. I've got lots more questions, but since this thread was more on the resolution issue, I'll go back to the other thread with them...

04/07/2004 07:30:48 PM · #42
Originally posted by dwoolridge:

Originally posted by ScottK:

I guess at this point it all has to be qualified by which version you're using.


I thought it was pretty clear that I'm using PS CS.


It was. :)

Originally posted by dwoolridge:

Originally posted by ScottK:

Originally posted by dwoolridge:

By the way, is your working space adobe rgb?

Yes. Any suggestions on whether that's good, bad or ugly would be appreciated. :)


Well, I suppose it's good if your monitor is calibrated to D65/2.2 and you're generating high-bit input in that particular space (or a device space converted to it) as you might when converting RAW files. There's no compelling reason to take low-bit input (i.e. sRGB JPEG) and convert to that space.

Just based on your file name, I'm assuming you're shooting JPEG, so converting to Adobe RGB is ill-advised. However, I only bring it up because the images you've uploaded to DPC look like they were saved directly while in the adobe rgb space. That's bad and ugly. You should treat the web/dpc like any target output device/space and do the appropriate conversion before saving your final web version. Again, I'll reiterate that when shooting JPEG, there's reason not to use Adobe RGB and stick to sRGB instead.


I want to ask more about this, but need to think on it a little...

Message edited by author 2004-04-07 19:32:16.
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