Photoshop’s Resolution Setting & Physical Screen size

[KostFan2]

Adobe’s Article: “Our Guide to PPI (Pixels per Inch) and Pixel Density”   
Adobe recommends customers use Resolution Sizes as follows:
QUOTE:

Here are a few rough PPI measures you can use for your project.

High-res pixels per inch.

High-res displays can handle more PPI on screen than the commonly held 72 PPI standard. If you’re displaying images or film on a large HD monitor, you can afford a far higher PPI level than your average laptop.

• A high pixel density can range between 100-140 PPI
• A very high pixel density starts off at 140 PPI

• High Pixel Density: A high pixel density can range between 100-140 PPI
• Very High Pixel: A very high pixel density starts off at 140 PPI

END QUOTE

However, I do not think that the article considers the physical size of the display and the upscaling performed by the manufacturer which causes pixelation that makes the image quality unacceptable.

The difference between a resolution setting of 100 vs 300 is roughly only 5MB additional file size, or slightly more computer space required.  However, the difference when those two images are displayed on a 55-inch display (the average size in USA for TVs purchased during the last 5 years) is very noticeable.

Have I missed something? If not, then perhaps the article should be updated.

Why? Data Loss:  Using 100 resolution vs. 300 resolution results in data loss roughly of 86%. Only 14% of the original data remains.

Big Screen Displays and 11 x 14 Prints: This is particularly important if showing an image on a 55-inch display or larger, or making an 11 x 14 print.

Above numbers will vary depending on the content of the image: what is in the photograph

What am I missing?

[didiermazier]

The only fixed measure of an image is its pixel numbers

Regarding the screen sizes it works as following

HDPI screen : if your screen is 55 inches (diagonal) the width is around 48 inches. So to get a clean image its width size must be at least 48 x 100  = 4800 px 

UHDPI : same math :  48 x140 = 6713 px

for printing it is another story.

resolution must be 2 to 2,5 the print screen.

For magazine with 150 screen a 9 inch width image you need at least 9x150 : 1350 px width image

Hope it helps

[KostFan2]

Dear @didiermazier 

Thank you for your answer. Please forgive the basic questions, but as @davescm knows, I am trying to really understand this resolution issue.

Question 1:

When you say

“48 x 100  = 4800 px” from where is the 100 coming from? and
when you say:

“48 x140 = 6713 px” from where is 140 coming from?

Question 2:

Based on the above, are you saying you would do the following:

Open Photoshop when you select Image/Image size you would enter “100” if it was HDPI . and 140 if it was UHDPI.

Is that understanding correct?

The reason this resolution issue is so important to me is that my client reviewed all of the edited image on his 27 inch 4k display and approved the purchase order.  2 weeks later he demanded a full refund because the pixelation was so bad on his 55 inch Sony A95L display.  That TV has what I have been told is a “state of the art” processor (Cognitive XR Processor) to handle upscaling to minimize pixelation.

I have over 15,000 other images for this client and other clients and I want to make sure that this situation is not repeated. 

Thank you for your assistance.

[davescm]

The article is misleading.

For screen display, ppi of the image is irrelevant. A 3000 x 2000 pixel image at 1000ppi will display exactly the same on screen as a 3000 x 2000 pixel image at 1ppi. All that matters on screen is that you have sufficient pixels to fill the display.

You mention TVs - they are likely to be HD screens (1920x1080 pixels), UHD screens (3840 x2160) or occasionally 8k screens (7680 x 4320). Displaying on any of those does not involve the ppi image value at all. The ppi value is held alongside the image, in metadata, and is used by the print driver to convert pixels to a physical print size on paper.

Note : There is in Photoshop Preferences a screen resolution setting. That is used to ensure View-Print Size works correctly.

Dave

[KostFan2]

@davescm 

Thank you for posting. You must have felt I did not understand your prior answer to me in my other post.  However, I did. I have edited my original post with the direct quote from the Adobe article so you can see how such an article confuses.  Also please see my response to didiermazier for the full details of what happened to me and why this is so important.

[davescm]

The Sony A95L is a 4k TV which means it has 3840 x 2160 pixels. That remains the same whether it is in its 55inch or 65 inch or 77 inch variation. 

If your images are 3840 x 2160 pixels no scaling will be required. Whether any processing is applied in the TV you cannot control. PPI does not enter into it, just as TV images have no ppi metadata. 3840x2160px at 1ppi will display the same as 3840 x 2160 px with 1000ppi. In fact on images prepared for screen use it is common to strip out the ppi metadata altogether - which is what export does.

Dave

[jane-e]

The article is misleading.

By @davescm

The article also appears to not be in the US pages at all. I wonder if it was pulled and Adobe forgot to pull the UK page?

I clicked the "hyperlink" link and got this alert. The first time I chose United States.

It took me here to a 404 page. Note that because I am in the US, I don't see the country code. I don't know what you'll see.

https://www.adobe.com/creativecloud/photography/discover/pixels-per-inch-ppi-resolution.html

I went back and this time chose "United Kingdom" from the alert. I got the UK country code and misleading information that UK viewers see.

https://www.adobe.com/uk/creativecloud/photography/discover/pixels-per-inch-ppi-resolution.html

There's more:

In the UK version, I followed the link to "DPI explained"

Again, choosing US took me to a 404 error. No country code because I'm in the US.

https://www.adobe.com/creativecloud/photography/discover/dots-per-inch-dpi-resolution.html

I had to choose UK to read the DPI article, which also has misleading information. Note the country code.

https://www.adobe.com/uk/creativecloud/photography/discover/dots-per-inch-dpi-resolution.html

Both of these pages are on the UK site, but the US site gives a 404 error. If you test this from outside the US, pay attention to the country code.

I also tested "fr" for France and it yields the 404 error.

Jane

[KostFan2]

@jane-e , @davescm , @didiermazier 
Sorry for the confusion.  The link to this article was sent to me by Tier II support at Adobe.  It is from Adobe’s UK site.  I had no idea it would cause Forum members issues. I have removed the link from the original post so other Forum members do not have a problem. I have also added a direct quote from the article

• I believe that if you click “United Kingdom” on the screen you should be able to read it.  https://community.adobe.com/t5/user/viewprofilepage/user-id/10909385
• I have spoken with Tier II support again and asked them to place a copy of the article on the US server. However, they are having trouble with that request.
• My description in the Original Post still applies.  

Thank you