Questions about setting for a large project

[aiur4]

Hello, I usually print a large image up to 60 inch at the longest but I have questions to clear some answers.

1. When do I use 16 bit or higer? Does it affect when I print it?

2. Do you think it's ok to set both color profile and color setting with ProPhoto?

3. What does send a 16-bit data do for printing?

4. For a long term storage, do you recommend higher bit and wider color space?

5. If I want to create a canvas with twice bigger than 60x44, do I still keep 300 PPI?

6. Is there a way to show preview with PSB files on MacOS with Apple Silicon?

7. What's the best way to reduce file size if I have more than 100 layers?

[Test Screen Name]

What is your printing technology? What is the material produced, and how is it viewed? (The reason for these questions is to find what resolution and quality you may actually need; 300 ppi is almost always not needed for large format work.  By the way, it's far too early to be using Apple Silicon for production work.

[davescm]

Hi

1. When do I use 16 bit or higher? Does it affect when I print it?

16 bits/channel divides the levels between the darkest pixel and brightest pixel value into 65536 steps (actually 32769 in Photoshop for internal processing reasons) whereas 8 bits per channel divides it into 256 steps. This means that gradients are smoother and there is less likelihood of visible stepping (banding) when processing the image.

As for printing, it depends on the printer and its driver. Not all are capable of 16 bit support. In reality that last step is rarely an issue as there is no further processing and the range of values between the darkest black and whitest white is more limited than the screen.

2. Do you think it's ok to set both color profile and color setting with ProPhoto?

Yes, but an image should never leave your PC with that profile. When sending elsewhere then always convert to a more universal profile (sRGB is most common for web use). Also be aware that ProPhoto can contain many more colours than can be displayed on current monitors. Personally I use Adobe RGB which has a good range, is displayable on my monitors.

3. What does send a 16-bit data do for printing?

As mentioned above, it will send the full 16 bits/channel data to the printer, but it relies on a printer and driver that will use it. Not all printers do.

4. For a long term storage, do you recommend higher bit and wider color space?

Yes, although personally I find Adobe RGB big enough for most real world images.

5. If I want to create a canvas with twice bigger than 60x44, do I still keep 300 PPI?

It all depends on viewing distance. There is no magic number. For images in a book 300ppi works well, for a wall poster viewed from further away it a waste as our eyes cannot resolve the pixels.

As a guide use this:

ppi required = 6878/Viewing distance in inches

6. Is there a way to show preview with PSB files on MacOS with Apple Silicon?

I don't know if a codec is available for PSB on the MAC (I use Windows)

7. What's the best way to reduce file size if I have more than 100 layers?

For the master file, don't. Disk space is relatively cheap, going back and recreating a file with lost layers is not. However, as mentioned above, don't work in unnecessarily high pixel dimensions.

Dave

[D Fosse]

Everything Dave said.

Just to give you a quick number - for a 60 inch print, anything between 100 - 150 ppi will work splendidly. Twice the linear size = half the ppi (because you'll be standing at twice the distance to view it comfortably).

[aiur4]

Well, actually, it's the opposite. I let people to watch my works very closely to see details.

[D Fosse]

OK, but 150 should still be enough. You can't see pixels at 150 ppi no matter how close you go. Consider a standard desktop monitor, like a 24 inch at 1920 x 1200. That's roughly 96 ppi. Can you see pixels? No, you can't.

The fact is that the 300 ppi number that everyone thinks of as a "requirement", is purely theoretical. It's based on a standard book/magazine print process, which uses a halftone screen frequency of 150 lines per inch. The theory is that with a pixel density twice that, it is not possible to make out the original pixels. Not even in theory. In other words - that's the upper limit where additional pixels make no difference.

And then this theoretical upper limit has somehow transformed itself into a perceived lower limit.

But the visual resolution is the halftone screen at 150 lpi. That's the level of sharpness and acuity. Whether you can make out individual pixels is not the same as sharpness.

Just to put it in context: if you go to the very top end of current full-frame cameras, a Nikon Z7, Sony a7r or Canon EOS R5, you get around 8000 pixels on the long side. At 60 inches, that's around 125 ppi. Nobody ever complained about resolution in those cameras.

[aiur4]

So even the high end printing labs use 150 PPI with 8 bit?

[D Fosse]

You misunderstand. Ppi relates to size, it cannot be considered separate from size.

Like this:

[Conrad_C]

aiur4 wrote:

1. When do I use 16 bit or higer? Does it affect when I print it?

3. What does send a 16-bit data do for printing?

Use 16 bits per channel if:

• You are using images captured at more than 8 bits per channel.
• You plan to make edits that make large changes to tone or color values.
• Your document has gradients or transitions that need to be very smooth.

If source images are only 8 bits per channel, changing the document to 16 bits per channel won’t improve quality but doubles the file size.

There is not much visual benefit to printing at 16 bits per channel, and there have been some bugs related to it, so I print at 8 bits per channel even though my documents are 16bpc and my printer driver supports 16bpc printing.

aiur4 wrote:

2. Do you think it's ok to set both color profile and color setting with ProPhoto?

It’s OK to use ProPhoto RGB as a document color profile, but only if you understand how it will be converted to the printer profile (if printing) or sRGB (if posting online). ProPhoto RGB and Adobe RGB are very good color spaces for editing and mastering, but are not good to use as typical output color spaces for print or screen.

The display, document, and print/export profiles are typically different, especially for professional work.

The Working Space profile used in Edit > Color Settings is a default, for documents that have no embedded color profile. If a document already has an embedded profile, the Working Space profile doesn’t affect it.

aiur4 wrote:

7. What's the best way to reduce file size if I have more than 100 layers?

You might be able to reduce file size of 100+ layer file by:

• Saving as TIFF with the ZIP compression option enabled. This takes a lot longer to save, but you can continue to work while Photoshop is saving.
• Editing at 8 bits per channel instead of 16 bits per channel, if you test 8bpc and find that image quality is acceptable after editing.
• Using a ppi resolution value no higher than actually needed for the expected viewing distance. Again, testing a small section of the print on the wall will help you determine how high of a ppi value is really necessary for the content in your image.
• Minimizing the use of Smart Objects, because those can add a lot to the file size.

[aiur4]

I used GFX 100 with 16 bit color. Can I justify to use 16 bit?

[Conrad_C]

aiur4 wrote:

I used GFX 100 with 16 bit color. Can I justify to use 16 bit?

The GFX 100 appears to be an excellent camera for large images, with a high resolution 10bpc sensor that can save a 16bpc file. If set that way, it would make sense to edit its images in 16bpc in Adobe RGB or ProPhoto RGB.

aiur4 wrote:

So even the high end printing labs use 150 PPI with 8 bit?

Many of the files received by high-end printing labs are 8bpc files, exported from 16bpc layered master documents. Again, we make a distinction between the bit depth in the file used for editing, and the bit depth in the file exported for printing. High end labs typically recommend 240–300ppi for smaller prints, but files intended for very large prints will often have a lower ppi that is proportional to the intended viewing distance, as D Fosse is saying.

You must reconcile conflicting goals that you have stated. If you want higher resolution and bit depth in order to preserve more image quality from an excellent camera with a large sensor, you must accept larger file sizes and your computer must have enough processing power, RAM, and storage to handle them efficiently. If you want lower file sizes, you must decide which aspects to compromise on, as listed at the end of my earlier post above.

[aiur4]

Do you think I should consider 16 bit if I use cameras with 14 bit color space?

[D Fosse]

"Do you think I should consider 16 bit if I use cameras with 14 bit color space?"

You can't really compare those two. Demosaicing and encoding into an output color space completely rebuilds the one channel raw file into a three channel RGB file. The higher the bit depth of that encoding, the better the result.

16 bit depth is the norm today and you should try to keep it in 16 bit during processing. This gives you headroom for adjustments without "stairstepping". The final output is often 8 bit (display, printers), but if you've worked in 16 bits up to that point, the final 8 bit values, 256 discrete steps per channel, will be optimal and evenly spaced without gaps.

A lot of people see file sizes as a problem. I usually say that if you do, you're in the wrong business. Raster image files are big and take up a lot of disk space; that's just the nature of the game. If your disks fill up, buy new disks. They're pretty cheap. And back up, always...

[Conrad_C]

It’s normal to use 16 bits per channel for any cameras capturing at more than 8bpc, simply because image editing applications such as Photoshop offer 8bpc and 16bpc but nothing in between. (Most cameras today are 10 to 14bpc.) So if you want to have all the tonal and color data available from the camera, 16bpc would be the usual choice.

But there is another way to think of this, especially if you are concerned that 16bpc files might be too large. It depends on what kind of a photographer you are: 

• If you are able to get the final image correct in camera (similar to shooting slide film), with only slight changes to tonal and color values before printing and exhibiting, 8bpc could be enough. 
• If you capture images that you plan to edit extensively in Photoshop, making significant changes to color values and to tonal values from the darkest shadows to the lightest highlights, then a 16bpc image would typically retain quality more effectively.