selmslie Loc: Fernandina Beach, FL, USA

The thread Recommended resizing parameters for digital images was opened by CHG_CANON in the new Advice from the Pros section to revisit the question of Resolution (links in next post) to clarify an earlier thread Resolution opened by TheDman.

The two threads cover essentially the same subject matter and both threads are basically in agreement. However, one significant point that was being made by TheDman was overlooked in the new thread.

TheDman tried to point out that only Adobe has made a big deal about the difference between resizing and re-sampling. Resizing the way Adobe describes it is a meaningless concept. He pointed this out to them and they admitted that they had been wrong about the dpi aspect of their documentation and software.

Because displays and printers have a fixed pitch, the only way to fit an image (also a fixed number of pixels) onto a screen or a sheet of paper is by re-sampling.

Re-sampling is a fairly trivial step and it is done instantly as you zoom in or out on an image on your display. The only time things get wonky is when you go above 100% and start to see pixelation. But with a 4K display its hard to see this until you pass 200%.

selmslie Loc: Fernandina Beach, FL, USA

CHG_CANON Recommended resizing parameters for digital images
TheDman Resolution
Adobe's response to TheDman: http://www.uglyhedgehog.com/t-511614-12.html#8664317

Adobe's response vindicates TheDman and shows that the excuse given for locking his thread was not valid.

Joe Blow

Yup. I'm in full agreement.

However, the word "re-sample", to me, suggests making repeat trips past that little table set up in the supermarket with cheese or crackers on it.

rehess Loc: South Bend, Indiana, USA

The reason given for locking his thread was that he already had his answer, and very firmly held it, so he was not asking to gain information, but apparently had disingenuous reasons for posing this question.

The discussion was all about his method of presentation and motives, not about his material, so the latest material is irrelevant to the previous discussion

selmslie Loc: Fernandina Beach, FL, USA

No, the reason (excuse) given for locking the thread was that, "I did not lock this thread despite having serious misgiving toward your obvious intent. ... Had you not done commented on Adobe I would have waited longer."

So it had absolutely nothing to do with already knowing the answer, as many of us already did.

Rongnongno initially unlocked the thread because he felt it was a worthy subject. He locked it because he felt it he could not tolerate TheDman for something he had been saying on another thread.

To make matters worse, Rongnongno broke a promise he made at the outset, "There will be no interference from any of the non mentors - including moderators -."

Rongnongno's action undermined his mentors and brought discredit to the integrity of the new section.

Despite having come up with the idea for the new section, he may not he the right person to remain as a monitor.

rehess Loc: South Bend, Indiana, USA

My opinion is that Rongo as section leader has been the motivation and unspoken agenda item all along. You may talk all you want about that - I have nothing further to say. The time to discuss that was before the section was created.

selmslie Loc: Fernandina Beach, FL, USA

If it is a better mousetrap then it will survive on its own merits.

If it doesn’t catch on it will be because it was not a good idea in the first place or because of Rongnongno’s own history.

Bill_de Loc: US

The biggest advantage of the new section, if it catches on, is that the threads may stay on topic ... unlike this one.

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selmslie Loc: Fernandina Beach, FL, USA

What do you suppose is the topic of this thread?

tdekany Loc: Oregon

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

But you can resize a higher MP image to a smaller screen size, without resampling. If you take an image from a D800 that is 7,360×4,912 and crop it, without resizing, to 1920x1200, it will "fit" a standard WUXGA HD display, which is also 1920x1200 in resolution, with no resampling needed. In this case Adobe's dpi specification is just a metadata tag without meaning or application.

Also, if you send a higher resolution or lower resolution image to a printer, most printer drivers (or raster image processors) will up/down sample the image to fit the image on the paper at the given resolution. A 6 mp image from a NIkon D70 is 6000x4000. At a desired print resolution of 300 ppi, you can print, without resampling, a 20x13.3 image. Without resampling the image, you can print a much larger image, like 60x40, but at a lower printer resolution of 100 ppi, with the print driver or RIP handling the "resizing" without resampling. However, if you need a higher resolution than the image has provided, say 200 ppi, then you have the option to resample the image to 12,000x8,000 px using an image resizing program, or the resizing algorithms in Photoshop, Lightroom or other image editing software, or let the printer driver/RIP resample it - so that you will be able to have enough "pixels" in the image to meet your image resolution requirement. The issue with up-sampling is that software is used to expand the individual "pixel" spacing, and it uses interpolation to take a good guess at what should be placed to fill in the new space between the old pixels. Resizing software NEVER increases resolution, but the better software will increase the edge contrast, or microcontrast, to give the viewer the perception of greater sharpness.

So, though I usually agree with you, Scotty, on this on I don't agree 100% - you can crop to resize to a given pixel count. It doesn't always have to be resampling.

selmslie Loc: Fernandina Beach, FL, USA

Cropping? Now that's a stretch, if you'll pardon the expression. If you do that to the image of a group of people, some of them will disappear.

The point is that dpi has no place in the calculation. If you display an image at 100% on a 1920x1080 image on a 19", 23", 25", 27", etc., monitor, the dpi will be different in each case. My monitor displays 3840 pixels over a 24.5 inch width - 156.73 ppi. So what?

So you agree that the ppi measurement is meaningless for displays. It is just as meaningless for prints. Everything has to get re-sampled/resized (only Adobe fans quibble over the difference) to get the whole image to fit.

Cdouthitt Loc: Traverse City, MI

I do a fair bit of resizing for my work projects, often times going as large as 10’+ from a standard 16-24mpx image from a dslr. Super graphics produced from the latest large format printers, uprezed in just photoshop is pretty darn amazing.

selmslie Loc: Fernandina Beach, FL, USA

Neither of the threads addressed the question of how much resolution you really need to perceive the image as sharp and not pixelated. That's not TheDman's fault. His thread got shut down before it got interesting.

An iPhone 4/4S Retina display has a pixel density of 326 ppi. See: APPLE'S NEW RETINA DISPLAY.

You might actually hold the iPhone about 10 inches from your face to look at an image because it's a small screen but you may have to put on your reading glasses..

With reference to the iPad's 132 ppi display you will see the statement that If you're holding the iPad further than 18 inches from your eyes, you're not at the optimal distance to appreciate the display's high resolution – "that high resolution is wasted."

As you back away from a screen, the displayed ppi becomes less demanding. Viewing a 300 ppi display from 10 inches looks no better than a 150 ppi display from 20 inches or a 75 ppi display from 40 inches. But in each case your angle of view for the entire image remains the same. The iPhone's 3.5 inch screen would have the same angle of view as a 7" screen or print viewed from 20 inches or a 14" screen or print viewed from 40 inches and so on.

So if we decide that 300 ppi is the goal for an 8x10 inch image to be viewed from 10 inches, it's easy to do the math: 8" x 300 ppi x 10" x 300 ppi = 7.2 MP. A 24 MP image is therefor more than 3x as much resolution as you would ever need. So if 24 MP is overkill, anything higher is gross overkill.

Assuming, of course, that you do no cropping.

Cdouthitt Loc: Traverse City, MI

I just checked...the last image I uprezed from 20mpx Canon DLSR was sized to 11400 x 17100 @ 150 (actual finished size was 76" wide x 114" high). Viewed from 5' away, it appeared very sharp and pleased the store owner and architect.