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Author Topic: Most favourable up-ressing percentage  (Read 14223 times)
hjulenissen
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« Reply #40 on: March 31, 2014, 01:53:24 AM »
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After reading this thread, I did re-examine my LR printing workflow and learned that if one does not check the resolution box to specify a printing resolution and checks the dimensions in the guides panel, the linear size and pixel dimensions of the printed image are shown (as illustrated below). In his LR4 book, Martin Evening suggests not checking the resolution box in which case LR will send the full resolution to the printer and the downsizing will be done by the printer driver. I think it would be better to initially leave the resolution box unchecked and obtain a readout of the print resolution. With the Epson printer, one would then enable print resolution and use 360 ppi if the indicated resolution is less than 360 and 720 for a resolution greater than 760.
If there really is a systematic benefit to choosing specific output resolutions when printing in Lightroom (depending on printer manufacturer) as has been stated by knowledgeable people here and elsewhere, it would be in line with the "make-things-work" philosophy of Lightroom to (as a default) make the sensible choice behind the scenes. I am not advocating removing the option of controlling things, only requesting that the first (default) option be "auto" (and that the algorithm does what Schewe & friends recommends).

It sounds like a simple algorithm?
If printer manufacturer == Canon
 base_dpi = 300
else
 base_dpi = 360

If image_dpi < base_dpi
 print_dpi = base_dpi
else
 print_dpi = 2*base_dpi

Quote
For best quality, it might be preferable to resize in Photoshop.
I assume that you mean "outside of Lightroom" and not specifically "in Photoshop".

I think it is interesting to know and understand how stuff works, when things start to break down, and how far quality can be stretched if one is willing to pay the price. Like you, I prefer the comfort of doing most of my stuff inside Lightroom, even if there might be some slight quality hit.

-h
« Last Edit: March 31, 2014, 01:59:37 AM by hjulenissen » Logged
Paul2660
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« Reply #41 on: March 31, 2014, 06:24:23 AM »
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I don’t know ... i was intrigued so I looked at it.  With no real GUI I just couldn’t bring myself into trying to figure out installation and the command line interface.

I totally agree. Appeared to be all command line.
Paul
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Paul Caldwell
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« Reply #42 on: March 31, 2014, 06:48:36 AM »
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One other question for the forum. Jeff in the past had recommended 240 dpi for larger prints 16 x 20 and up and 1440 on the printer, Epson. I have always worked on the principal that Epson's will do best with 180,240,360 and 720 for the print and 1440 dpi for the printer on larger prints.

For 20 x 30 and up most times I will use 240dpi for the print and 1440 on the printer as uprezing to 360dpi most time just does not give the best looking output.   Phase One images I tend to use 300dpi but I can get them to 360 easily enough.

Personally I just have never found a good software solution for uprezing that holds the finer details that the Epson printers can produce.   Uprezing say a 20 x30 at 240dpi to a 40 x 60 at 240 or 360dpi. For that I tend to go to 180dpi.

Paul
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Paul Caldwell
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BartvanderWolf
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« Reply #43 on: March 31, 2014, 07:24:12 AM »
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I think it is interesting to know and understand how stuff works, when things start to break down, and how far quality can be stretched if one is willing to pay the price. Like you, I prefer the comfort of doing most of my stuff inside Lightroom, even if there might be some slight quality hit.

Hi,

Simpler workflow aside, resampling alone will make a significant difference to output quality (it usually lowers micro-detail contrast). Whether it's significant enough for an individual user/client is hard to say.

What is obvious is that so many people report significantly better output quality from the exact same file when printed with e.g. Qimage (which automatically up-samples to 600 or 720 PPI, then sharpens) versus Photoshop (which lets the printer driver resample, usually with bi-linear, sometimes with bi-cubic). So the anecdotal evidence shows that it can be a significant difference, although it obviously also depends on the specific image content.

When we accept the importance of better re-sampling, and we're going to invest some effort to achieve the required image size, then why not use the best option available that we can use (provided that the workflow remains workable).

The re-sampling algorithms of Lightroom use an unknown method (the up-sampling appears to push resolution yet avoid adding edge halos, maybe it's adaptive), with a few optional predetermined levels of re-sharpening at the final output size (which can be simpler if there are no added halos). Reading the reactions from users, LR seems to produce an acceptable level of output quality for them, although it's not clear whether they know if and how much better it could be ...

I've compared 300% upsampled output from Lightroom 5.3 and Qimage Ultimate (Fusion resampling), and indeed it's no longer all that different since LR up-samples to native printer resolution and then adds sharpening. Things do get better when one uses dedicated resampling, e.g. EWA Lanczos Radius or even more of a difference from PhotoZoom Pro which enhances edge resolution, and when applying dedicated sharpening to the resized for output image data. The more recent implementations of Perfect Resize (which seems to have come down in price as well) also offer some resolution enhancement and post resize sharpening. Being able to produce a print sized output file that allows further detail sharpening will add another step up for output quality, e.g. an EWA Lanczos Radius + Topaz Labs Detail.

Cheers,
Bart
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BartvanderWolf
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« Reply #44 on: March 31, 2014, 07:56:32 AM »
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One other question for the forum. Jeff in the past had recommended 240 dpi for larger prints 16 x 20 and up and 1440 on the printer, Epson. I have always worked on the principal that Epson's will do best with 180,240,360 and 720 for the print and 1440 dpi for the printer on larger prints.

Hi Paul,

Jeff no longer recommends that. Basically he now agrees with up-sampling to the printer's native resolution, 360 PPI or 720 (with finest detail selected) for Epson, and 300 PPI or 600 PPI for Canon / HP / and similar. It produces better quality when better resampling routines are used than what the printer driver uses, and it allows to add post-resize sharpening at that exact native resolution.

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For 20 x 30 and up most times I will use 240dpi for the print and 1440 on the printer as uprezing to 360dpi most time just does not give the best looking output.   Phase One images I tend to use 300dpi but I can get them to 360 easily enough.

360 PPI should be superior to 240 PPI (assuming the use of proper resampling algorithms), but you need to re-sharpen after re-sampling. Phase One's Capture One uses a relatively simple (looks like bi-cubic) resampling. While better than what most printer drivers use, it would be awesome if they adopted some of the suggestions made in this thread (with a few enhancements).

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Personally I just have never found a good software solution for uprezing that holds the finer details that the Epson printers can produce.   Uprezing say a 20 x30 at 240dpi to a 40 x 60 at 240 or 360dpi. For that I tend to go to 180dpi.

The printer driver will then automatically upsample from 180 to 360 PPI (= native printer driver resolution) with an inferior (usually bi-linear) algorithm, do no re-sharpening, and leave unused quality on the table. You should be able to do better!

Cheers,
Bart
« Last Edit: March 31, 2014, 08:52:44 AM by BartvanderWolf » Logged
Paul2660
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« Reply #45 on: March 31, 2014, 09:20:22 AM »
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Bart:

Thanks for the info.  I will try this in the future.

Paul
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Paul Caldwell
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Jim Kasson
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« Reply #46 on: March 31, 2014, 10:36:44 AM »
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The printer driver will then automatically upsample from 180 to 360 PPI (= native printer driver resolution) with an inferior (usually bi-linear) algorithm, do no re-sharpening, and leave unused quality on the table.

Bart, as of three years ago, it was even worse that that with the Epson 3880 driver; it used nearest-neighbor.

http://blog.kasson.com/?p=487

Jim
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bjanes
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« Reply #47 on: March 31, 2014, 10:44:52 AM »
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That's correct, even though the specific answer mentioned above was in relation to upsampling, deconvolution sharpening, and down-sampling again to the original size. Down-sampling image detail that exceeds the highest spatial frequencies of the smaller size will lead to aliasing artifacts, and the various resampling filters produce different artifacts as a result. Bi-cubic sharper produces horrible aliasing, even regular bicubic down-sampling improves with a prior blurring of the highest spatial frequencies. In the specific up/down-sampling suggestion, there will be little image detail to cause trouble (even with bicubic) because there is not much aliasing potential.

Thanks for the detailed reply. The information concerning alaising when downsizing with bicubic sharper is of particular concern to me, since I am using the Nikon D800e, which does not have a low pass filter and thus already has alaising in that regard.

As for Output sharpening use, this video offers a reasonably good workflow explanation (using the older version of Detail, the newer version offers more tools such as masking thus reducing the need for Photoshop), although I'd also pay more attention to the "Deblur" panel, because it can mitigate some of the up-sampling blur. Good up-sampling generally should try to avoid adding big halos, and therefore produces low detail contrast which can be compensated for by deconvolution.

I did watch the video on output sharpening, which somewhat tries one's patience, since the presenter takes 45 minutes to cover what could be covered in 10 minutes at most. His approach is basically sharpen to taste using the small details slider when viewing the image at 50 to 75%. I was unable to view at 75%, since the zoom tool goes from 50% to 100% and one can not specify the zoom directly as one can do in Photoshop.

This approach is quite different from that of the Fraser-Schewe output sharpening approach where the parameters are mechanistic and determined by the image size and resolution according to the "magic numbers" obtained via laborious testing involving the printing of many images. If one starts with a 36 MP image rendered into 16 bit ProphotoRGB and then resizes to 720 PPI and adds a surface mask, the working image is well in excess of 677 MP. Even saving this image in case the parameters need to be adjusted for the final print takes a long time if one is using ZIP compression. This is where the parametric workflow if Lightroom really shines.

Regards,

Bill
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BartvanderWolf
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« Reply #48 on: March 31, 2014, 10:48:55 AM »
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Bart, as of three years ago, it was even worse that that with the Epson 3880 driver; it used nearest-neighbor.

http://blog.kasson.com/?p=487

Hi Jim,

Indeed, NN is exceedingly primitive. Maybe it's still that way, but I do not have an Epson printer so I cannot check it without tasking it to others.

Anyway, I avoid it and get much better results than what's produced on average. Of course for high volume work one may choose a slightly different workflow, but a lot can be automated with (drag-and-drop) batch processing.

Cheers,
Bart
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BartvanderWolf
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« Reply #49 on: March 31, 2014, 12:03:53 PM »
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Thanks for the detailed reply. The information concerning alaising when downsizing with bicubic sharper is of particular concern to me, since I am using the Nikon D800e, which does not have a low pass filter and thus already has alaising in that regard.

Hi Bill,

There are several things happening here. First there is inevitable aliasing due to under-sampling of the optical projection of our scene in front of the camera. Even cameras with an OLPF will usually produce some aliased results (but with lower amplitude) in the plane of best focus. That very high spatial detail is now converted into larger than Nyquist aliases. It's a fact of life, when using discrete sampling.

Next is the aliasing we create when we further reduce the sampling density of that already aliased data. Now all spatial detail smaller than the Nyquist frequency of the smaller down-sampled image grid will contribute to aliasing. Most of this aliasing will be avoidable to a large degree, but only if we use precautions (pre-filtering and good quality algorithms, using linear gamma also helps).

On my webpage about various down-sampling algorithms you can see that Bicubic Sharper produces somewhat higher sharpness (the 'rings' in the center extend slightly further, also into the corners) but also more aliasing artifacts than most other methods.


Bicubic Sharper



Lightroom 5.3

Lightroom does a pretty decent job when down-sampling, so as long as the aliasing at capture is small enough, it won't interfere with down-sampling for e.g. web-publishing.

Technically, an EWA Robidoux with gamma 1 downsampling is even cleaner (especially for color), but very close to Lightroom as far as resolution is concerned:

EWA Robidoux (Gamma=1 during resampling)

Make sure to watch these images at 100% zoom in your browser. Browser resampling is pretty crude as well, and will fall flat on its face with such critical test images.

But up-sampling requires a different approach compared to down-sampling.

Cheers,
Bart
« Last Edit: March 31, 2014, 12:10:29 PM by BartvanderWolf » Logged
NicolasRobidoux
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« Reply #50 on: April 06, 2014, 01:23:43 AM »
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If you magnify the zone plate downsample done with the EWA Robidoux filter through linear light, you can see that this filter straightens almost straight vertical and horizontal lines with too much eagerness.
Not surprising, because it was designed to do exactly that.
Arguably, this is fine when processing images of buildings and keystoning was corrected. But not so fine otherwise: it leads to staircasing (as Bart noticed).
-----
At some point, I'll add another member to the Robidoux set of Keys splines filters for EWA (Elliptical Weighted Averaging) resampling. Maybe this one: http://www.imagemagick.org/discourse-server/viewtopic.php?f=22&t=19823&start=30#p109820
« Last Edit: April 06, 2014, 01:25:33 AM by NicolasRobidoux » Logged
NicolasRobidoux
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« Reply #51 on: April 06, 2014, 01:34:29 AM »
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If you read between the lines of the rather terse technical specification (which sneaks in linear operator theory---dual norms etc), this is a filter that should be pretty good at preserving midtones near sharp features.
But I've not tested it enough to know.
« Last Edit: April 06, 2014, 01:42:20 AM by NicolasRobidoux » Logged
bwana
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« Reply #52 on: April 11, 2014, 11:05:13 AM »
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As I am rather naive in the tools available, I have stuck to LR . I am interested in using a better output workflow. Either going with perfect resize and then sharpening with topaz detail OR printing directly through LR using qimAge fusion.  I am still unclear on the steps for each workflow-and the considerations necessary to properly choose the right amount of sharpening.

Many references state that you cannot judge output sharpening on the display before printing even if you look at the image at 300% (the scaling necessary to view a 300 dpi image on a 100 dpi screen).

I wonder if Bart or another expert printer could share a link or perhaps a few details as these would be appreciated by a neophyte.
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BartvanderWolf
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« Reply #53 on: April 11, 2014, 12:48:34 PM »
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As I am rather naive in the tools available, I have stuck to LR . I am interested in using a better output workflow. Either going with perfect resize and then sharpening with topaz detail OR printing directly through LR using qimAge fusion.  I am still unclear on the steps for each workflow-and the considerations necessary to properly choose the right amount of sharpening.

Hi,

There are several routes one can take to improve the output quality of images coming from LR. It depends on the required results, e.g. large volumes or single masterpieces, which route is to be preferred.

When large volumes are anticipated, or various sizes for the same image, then Qimage is probably the better route because it can do the nesting and resizing automatically and it sharpens after the resizing. All it requires is a high quality TIFF file as input. That file can come from LR, but can first be improved by using Photoshop (or another host program that can use PS plug-ins) and be treated with Topaz Labs Detail (currently available with a 50% discount) as Creative sharpening tool before Qimage does its work. TL Detail does a much better job than LR when it comes to Creative Sharpening. Horses for courses.

When not using Qimage, the output file needs to be resampled to the Printer's native PPI, i.e. 300/360 PPI or 600/720 PPI, with another application, because the printer driver will otherwise do it, and not very well. One can use dedicated resampling software for better results, e.g. ImageMagick, or PhotoZoom Pro, or Perfect Resize. When you hold back a bit on post resampling sharpening, then TL Detail (with mostly deblur and small detail enhancement) can again be used for that Output Sharpening purpose.

That's all.

Quote
Many references state that you cannot judge output sharpening on the display before printing even if you look at the image at 300% (the scaling necessary to view a 300 dpi image on a 100 dpi screen).

I think that's a bit misleading. Of course at the bloated display size, the sharpening will look different than at the smaller print size. As such it is indeed hard to predict how it will look. However, it's not that difficult to learn how that enlarged sharpening result will translate to the print. It's called experience.

When applying output sharpening, one mostly attempts to counteract the blur caused by resampling to the output size, and add a bit extra to compensate for additional losses that have yet to occur, as a result of the printing process and medium used. As it happens, all that's required is good quality sharpening at the smallest detail levels, so it becomes a simple job of adding enough halo artifact free sharpness and contrast to the already resized micro-contrast. Because we often up-sample before output sharpening, it should be relatively easy to see how far we can go before the detail starts to look obviously weird.

Cheers,
Bart
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alifatemi
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« Reply #54 on: June 20, 2014, 09:26:44 AM »
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My response "no scaling after sharpening" was in reference to do image resampling before sharpening...if you were to then downsample then of course you would want to add sharpening because downsampling introduces softness.

Personally, since I use Lightroom (and usually large captures) the only resampling I do is in the LR Print module and I apply output sharpening where LR upsamples 1st and then sharpens...

As for the upsampling %'s, I've pretty much moved away from that (in part because of Bart's tests) and also since I don't do upsampling in Photoshop for the most part-although Photoshop CC's new "Preserve Details" option in Image Size is very interesting. If I were to need to do a massive upsample of a small original, I would prolly take a look at doing it in PS CC.



But in LR, in Develop module we first apply lots of sharpening/creative sharpening then we move to print module for upsampling then again using output sharpening just before printing so at least in LR, like it or not, part of sharpening happens before resampling. Am I right?
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BartvanderWolf
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« Reply #55 on: June 20, 2014, 11:47:36 AM »
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But in LR, in Develop module we first apply lots of sharpening/creative sharpening then we move to print module for upsampling then again using output sharpening just before printing so at least in LR, like it or not, part of sharpening happens before resampling. Am I right?

Hi,

Indeed, the sharpening/Clarity/tonal contrast/etc. adjustments in LR take place before resampling to the final output size. That does allow you to preview the adjustments at the 100 % zoom size of the original image, but you need to use your imagination/experience to judge how that will work out at the final size after final resampling/output sharpening and print.

A zoom setting to preview the image at the  final output size would be nice, but such functionality was also removed from Photoshop CC (a 'print size' button is still present in Photoshop CS6 on Windows OS) because it apparently generated too many support questions about how to set up the system.

Cheers,
Bart
« Last Edit: June 20, 2014, 12:46:01 PM by BartvanderWolf » Logged
Slobodan Blagojevic
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« Reply #56 on: June 20, 2014, 01:26:46 PM »
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... A zoom setting to preview the image at the  final output size would be nice, but such functionality was also removed from Photoshop CC (a 'print size' button is still present in Photoshop CS6 on Windows OS) because it apparently generated too many support questions about how to set up the system.

Hi Bart, it seems that, after numerous complaints, both CC and CS6 now have a View menu option "Print Size." Not a button, but the function is the same.

For it to work properly, however, one has to set PS "Preferences > Units & Rulers > New Document Preset Resolutions > Screen Resolution" to the monitor's native resolution (my iMac 27 is, for instance, 109 ppi).
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Hening Bettermann
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« Reply #57 on: June 20, 2014, 01:35:59 PM »
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Hi,
[...]

A zoom setting to preview the image at the  final output size would be nice, but such functionality was also removed from Photoshop CC (a 'print size' button is still present in Photoshop CS6 on Windows OS) because it apparently generated too many support questions about how to set up the system.

Cheers,
Bart

PhotoLine has got it, menu View > Original Size. I find the name misleading, but it's there.
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Tim Lookingbill
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« Reply #58 on: June 20, 2014, 11:02:00 PM »
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I just discovered a neat way to uprez (and view the results at 100% and tweak capture sharpening) in ACR 6.7 CS5 and then see the desired output sharpening with one click in Photoshop by first choosing in ACR's resolution change dialog box (by clicking below the frame) and choosing Glossy Paper/High sharpening or the other sharpening options. This option wasn't in CS3 and I'm glad I found this because it motivates me to start working in CS5.

I've been using this method for posting downsized for the web 700pixel/long end using Bridge's "Image Processor..." and it seems to do a really good job of turning my 6MP PEFs into 25MP images and/or sharpening for web. I can adjust the level of crispyness sourced from ACR by either not uprezzing in ACR and just choose the sharpening options and view in Photoshop or change the sharpening options and go straight to "Image Processing...".

I always hated to have to open my 6MP PEF's in Photoshop only to get a different look to sharpness due to ACR's "only accurate at 100%" views and then have to downsize in Photoshop and resharpen for the web. Saved a lot of steps using this method and I get pretty consistent results as long as I capture sharp in ACR viewing at 100%.

« Last Edit: June 20, 2014, 11:07:58 PM by Tim Lookingbill » Logged
NicolasRobidoux
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« Reply #59 on: June 25, 2014, 09:22:43 AM »
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Bart:
I am starting to see why you like (I think) EWA Robidoux. Here is what is does with sigmoidization.
Code:
magick QuarterZoneplate.png -set colorspace sRGB -colorspace RGB +sigmoidal-contrast 5,84% -distort Resize 230% -sigmoidal-contrast 5,84% -colorspace sRGB -quality 99 230.robidoux.s.5.84.jpg
Not very different from your own. The one's that's different is the one obtained by enlarging through linear light, which of course is generally not recommended.
« Last Edit: July 05, 2014, 03:04:41 AM by NicolasRobidoux » Logged
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