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Author Topic: Uprez startin from a raw  (Read 1795 times)
Samotano
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« on: January 30, 2011, 12:18:46 AM »
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I need to uprez an image because I am going to make a large print.  I recall Jeff Schewe suggests to uprez when the resolution is below 180ppi.  Now I'm a bit confused because in camera raw/LR one has the choice of changing the resoltion.  Can someone clarify this for me?
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k bennett
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« Reply #1 on: January 30, 2011, 08:15:21 AM »
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There are two things going on here with numbers. The important one is the total number of pixels (pixel dimensions), expressed like "4800x3600 pixels." The other number is called resolution and it's defined as the number of pixels per inch in the final product. So an image with the pixel dimensions 4800x3600 will have a resolution of 16x12 inches at 300 pixels per inch. Note that resolution requires BOTH the inches and the pixels per inch numbers, otherwise it's meaningless.

Please also note that changing the "Resolution" does not have any effect on the Pixel Dimensions. I can define the resolution of the above photos as 180 pixels per inch and get a print of 26.67x20 inches, but note that the pixel dimensions don't change. (I can also define the resolution as "1 pixel per inch" and make a 4800-inch long print, but it might not look so good...)

So when Jeff talks about resolution dropping below 180 pixels per inch, what that means is the your final print dimensions in inches will be large enough that the pixels per inch are <180. For example, trying to make a 36x48 inch print from our file above will result in a resolution of 100 pixels per inch from the original file. In that case, what you want to do is increase the pixel dimensions enough so that you have a resolution of 180 pixels per inch.

Is this clear as mud yet?  Smiley
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Schewe
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« Reply #2 on: January 30, 2011, 12:50:37 PM »
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I recall Jeff Schewe suggests to uprez when the resolution is below 180ppi.

Try reading this: The Art Of The Up-Res
(sorry the figures are a bit bad because of the way the magazine converted my supplied CMYK files :~(

Bottom line, you can easily do a 200% upsample with most digital captures. It takes some special techniques to optimize the images. If the starting image is technically excellent (exposure, focus, sharpness, etc.) you may be able to go up 400%. Just remember that as you upsample the image, you upsample any defects as well. You should do retouching AFTER you upsample, not before. I also suggest starting the upsampling in Camera Raw with proper capture sharpening and do any additional upsampling in Photoshop after the ACR upsampling. Some cameras don't offer any additional upsampling in the Workflow Options setting in ACR. In that case stick to Photoshop.
« Last Edit: January 30, 2011, 12:52:17 PM by Schewe » Logged
Pete Berry
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« Reply #3 on: January 30, 2011, 04:15:56 PM »
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Try reading this: The Art Of The Up-Res
(sorry the figures are a bit bad because of the way the magazine converted my supplied CMYK files :~(

Bottom line, you can easily do a 200% upsample with most digital captures. It takes some special techniques to optimize the images. If the starting image is technically excellent (exposure, focus, sharpness, etc.) you may be able to go up 400%. Just remember that as you upsample the image, you upsample any defects as well. You should do retouching AFTER you upsample, not before. I also suggest starting the upsampling in Camera Raw with proper capture sharpening and do any additional upsampling in Photoshop after the ACR upsampling. Some cameras don't offer any additional upsampling in the Workflow Options setting in ACR. In that case stick to Photoshop.

Jeff, I found your article very informative, but I have always uprezz'd to 300 ppi for my ipf5000 using the "bicubic smoother" option as the final step in PS after cropping, if needed, to output size, followed by output sharpening.

Unless I'm missing something, ACR 6.3 has no choice of bicubic algorithms in Workflow Options, so I assume it uses standard "bicubic" mode. Also, ACR's crop tool has no linear or aspect ratio settings I can find which makes it essentially useless to me, and if I crop later, having resampled first in ACR, have to resample again in PS for printing. So set me straight here, por favor!

Also, what's your current take on incremental sharpening? Your (rather dated!) article addressed the point, but I got the impression subsequently that the development of the "bicubic smoother" upsampling algorithm eclipsed that. What's your current opinion here?

Thanks for sharing your wisdom,

Pete
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Schewe
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« Reply #4 on: January 30, 2011, 04:29:33 PM »
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Unless I'm missing something, ACR 6.3 has no choice of bicubic algorithms in Workflow Options...

Yes, you are missing something. ACR/LR uses and adaptive Bicubic that automatically switches between Bicubic (so small resamples) and Bicubic Smoother for up and Bicubic Sharper for down. The trick is that it seamlessly blends between the 3 flavors depending on the amount of the resample...which is something you can't do in Photoshop.

Quote
Also, what's your current take on incremental sharpening? Your (rather dated!) article addressed the point, but I got the impression subsequently that the development of the "bicubic smoother" upsampling algorithm eclipsed that. What's your current opinion here?

"incremental sharpening"? I talk about doing a special sharpening after upsampling but that isn't related to the resampling algorithm. Are you confusing the sharpening with step interpolation? Different animals...and yes the article is dated. Did that make it less useful for you? It's still relevant.
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Samotano
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« Reply #5 on: January 30, 2011, 05:42:56 PM »
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Thanks!  That clears the confusion.
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k bennett
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« Reply #6 on: January 30, 2011, 06:02:47 PM »
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. Also, ACR's crop tool has no linear or aspect ratio settings I can find which makes it essentially useless to me,

In ACR, hold down the crop tool with your mouse, and you'll get a drop down menu with various aspect ratios.
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Pete Berry
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« Reply #7 on: January 30, 2011, 08:42:54 PM »
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Yes, you are missing something. ACR/LR uses and adaptive Bicubic that automatically switches between Bicubic (so small resamples) and Bicubic Smoother for up and Bicubic Sharper for down. The trick is that it seamlessly blends between the 3 flavors depending on the amount of the resample...which is something you can't do in Photoshop.

"incremental sharpening"? I talk about doing a special sharpening after upsampling but that isn't related to the resampling algorithm. Are you confusing the sharpening with step interpolation? Different animals...and yes the article is dated. Did that make it less useful for you? It's still relevant.

Jeff, please pardon the confusion of an old guy who's about ready for the big ice flow ride if any can be found these days. I thought I had read your article fairly well, but the 71 year old brain just didn't seem to hold on to much at the time. Read it again - answered my questions, along with a re-read of your first reply to this thread, and yes, it remains useful and relevant in spite of being a bit dated.

And yes, the "incremental sharpening" thing should have been "incremental resampling", or step interpolation.
 
And thanks, k bennett, for the tip about uncovering the aspect ratios in ACR crop tool - I had tried left and right clicks to no avail.

Pete

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