images not sharp unless zoomed to default percentages

[marks60810224]

Images are sharp only with the Zoom In and Zoom Out defaults or Fit Screen.

Most importantly, they're unsharp when at Print Size.

Anything I can do about this?

(Windows 7)

Thanks.

[davescm]

The only zoom level at which you can judge sharpness is 100%. That maps one image pixel to one screen pixel.

Any higher uses interpolation to map a single image pixel to more than one screen pixel - any lower does the same to map multiple image pixels to screen pixels. At zoom levels below 66.7% it gets worse as the image preview is blended using 8 bit previews which can start to alter the appearance of blending modes.

Print size should only be used to give an idea of how big things will look - not how sharp

Dave

[marks60810224]

Thanks for that info.

However, 100% is too large to view the image. And though other percentages may not be (as you mentioned) fully sharp, at least they are excellent to my eye. But only the preset zooms.

In other words, if I'm at the preset zoom of 33.33%, then, to my eye, it looks fully sharp. But if I zoom to, say, 34% or 32% then the image appears soft.

For Print Size, for me it happens to be 26.2%, But that's not as sharp as either 25% or 33.33% that are the below and above closest sharp neighbors. I wish I could get Photoshop to show 26.2% as just as sharp.

[marks60810224]

P.S. I'm not using Print Size to evaluate sharpness, but rather to see what the colors and tones look like at that size and to see what small details I might need to work on for a print that size. Then, while I'm at that size (especially for evaluating details), I'd like to happen to look sharp (as sharp to my eye as the default percentages appear).

[davescm]

Careful on the tones - as said above, blending at zoom levels below 66.7% uses 8 bit previews. Depending on how your layers are built up and on the content, you may see a difference.

On the 25% vs 26% or 24% difference I can also see that, but it is most likely just the difference between a fairly straightforward mathematical interpolation e.g. bringing a 16 pixel block into 1 screen pixel  and a more complex interpolation that has to blur between pixels.

Dave

[marks60810224]

Thanks very much. That's great info.

This issue of the tones and colors also interests me now that you've told me about it. The images don't have layers usually, so do you think the smaller zoom could still be very inaccurate? Also, aside from color images, there are black and white images, which (if I understand correctly) would be only 8 bit anyway, so would zoom size affect the tones in the sense you're speaking of?

At 66.7% zoom, even on a 27" 2560 x 1440 monitor, you can see only a portion of a 5616 x 3744 image.

Also, evaluating tones and colors at such a large zoom (a zoom that displays the image much larger than it would be in print or on the web) would be perceptually misleading, because the human eye regards a larger image as lighter and to have less contrast.

What I notice is that images seem darker and with more contrast (and maybe more saturated?) when viewed at smaller size. I've always thought that is quite natural, because (1) it's harder to "see into" a smaller image so it seems darker and (2) the tones and colors are closer together in a smaller image so they seem to have more contrast (easily we can see that at larger zooms the image starts to seem flat in contrast).

There are two cases:

(a) Preparing for web viewing, in which case the image "is what it is" at a given size, so adjusting its tones and colors for (at least approximately) that size shouldn't require factoring for the bit reduction inaccuracy you mentioned.

(b) Preparing for printing. Here, of course, the goal is for the image in Photoshop to best match how it will look in the print. And for that, I would think your point about reduction inaccuracy is very important.

[davescm]

Hi

For 99%+ of images - particularly flattened images with no layer blends you will not see a difference in the switch to less than 66.7%. Where you may see it is things like star fields - where the pin points of light can change dramatically or sometimes the blending of multi layered gradients involving several blend modes where blending in 8 bits can introduce changes to the blended preview compared to blending in 16 bit. In day to day images it will not show.

As long as you are aware of it, then you can zoom in and pan around for a quick check, and understand why if you see a change.

You mentioned B&W being 8 bit. B&W can also use 16 bit.

Dave

[marks60810224]

Oops, yes, my b/w is still at 16 bit.

About pinpoints, yeah, I have noticed that perceptually it is hard to gauge their accuracy.

Anyway, I guess I should consider it answered that there is not a way to get Photoshop to not blur between the default percentages?

[marks60810224]

PS. When I say my b/w is still at 16 bit, I mean that after I do Image>Adjustments>Black & White, then Image>Mode still shows 16 Bits/Channel. So I guess I'm all good?

[marks60810224]

By the way, I find it curious that Photoshop blurs between the default percentages, but browsers and Windows applications don't. I would think that Photoshop would do a better job than plain common applications.

[davescm · Accepted solution]

Hi

No you can't avoid that minor blurring

Yes your 16 bit B&W is OK.

Dave

[marks60810224]

Thanks very much for your help, Dave.

[davescm]

You're welcome

Dave

[gener7]

Just curious. Do you have Photoshop set up so that the onscreen rulers matches a physical ruler?

You basically take the monitor's screen resolution in ppi (mine is 114 ppi) and enter it here:

Then View > Print Size will adjust the zoom for you no matter the image print resolution.

[marks60810224]

Yes, I have had it set up that way. Thanks very much, gener7, for mentioning it.

Actually, I have it set up this way:

Print Resolution: 416 (5616 image pixels across a print with width of 13.5 inches)

Screen Resolution: 109 (2560 screen pixels across the width of my monitor)

[marks60810224]

PS

But I actually don't use Print View (26.2%) because it bugs me seeing the image softened, so instead I just use 25% which is as close as I can come.

[gener7]

Ok, good to know. Photoshop had that number glued to 72 for a while, so many are surprised that they can do this.

Hope the work goes well for you.

Cmd/Ctrl + and - is great for incremental zoom levels because it keeps the image centered.

Gene