Why 16 bit pixel depth feels so slow vs Affinity Photo?

[kirkr5689]

I can't really use Affinity Photo.  Lacking  scripting and automation a lot there .     But I always wonder why there is basically no difference 8, 16 pr 32 bit  the document is there.    While in Photoshop anything  like 4k image and 16 bit  is instantly painfully slow  vs 8 bit ?     Especially with smart objects  containing  higher res images inside ?   Seems good GPU vs noGPU  gives no influence on this at all.

Is there any tricks to improve performance for 16 bit image editing?  Special formats  for linked smart objects maybe?   I noticed pngs are slow .  Maybe something extra?  

[rayek.elfin]

...and are you aware that Photoshop's 16-bit mode is actually not a true full range 16-bit mode either? It only holds 0-32768 values, while Affinity Photo, PhotoLine, Krita, Gimp, and any other image editor with 16-bit support supports a range of 0-65535 values.

If a 16-bit file is loaded into Photoshop it is silently converted and degraded to lose half its values. 0-1-2-3-4-5-6-7-8-9 converts to 0-0-2-2-4-4-6-6-8-8 in Photoshop's 16-bit mode.

This was done when the 16bit mode was first introduced in the late 90s to improve performance and simplify calculations in code (since it provides a midpoint to the range and allows for faster math: bit shifts instead of divides), and it didn't matter 30 years ago seeing that nothing really produced such files with a full 16bit range anyway. Of course, that is no longer the case. It does become a problem in game and VFX depending on the context.

Anyway, I agree that Affinity works faster with those files. A bit painful once we understand that Photoshop's 16-bit files are actually degraded to half values, for which the original reason was to increase performance in the first place!

But perhaps this has been fixed in the past year? Does anyone know? I haven't kept track, since I never use Photoshop's 16bit mode due to this 'optimization'.

[D Fosse]

This sounds like lack of computer resources, most likely insufficient scratch disk space.

Please post the full Help > System Info from Photoshop.

[rayek.elfin]

I can confirm that Photoshop is just slower to respond to adjustments compared to Affinity Photo or PhotoLine (the last one doesn't even benefit from CUDA or a fast GPU for its calculations!). 

Even a simple Curves adjustment layer takes more time to complete and update than other image editors with the same 16 bit image, and on the same system. 

As a matter of fact, having to convert the image to a Smart Object to use a live effect (not necessary in other apps, btw!) such as a Gaussian Blur degrades performance further. The destructive Gaussian Blur filter responds faster than the live effect in Photoshop.

My Windows system runs on fast M2 drives, loads of free drive space, 128GB ram, a fast CPU, and a 5090 GPU. 

That's just the nature of the beast, i.e. Photoshop. It's slow compared to other software with basic operations (at least, based on my Photoshop running on Windows experience).

[D Fosse]

Well, don't know what to say. A curves layer is absolutely instant and real-time responsive here. Or several curves layers, or any other adjustment layer. And I work with big files, up to several GB.

[rayek.elfin]

That is interesting, and urges me to investigate further. I will get back to you later this week 🙂

[kirkr5689]

here is my system  

[D Fosse]

@kirkr5689 

First of all, dual graphics in laptops is a known potential conflict. It may work or it may cause problems, depending on how the manufacturer configures the operating system and the two GPU drivers. Disable the integrated GPU as per section 6 & 7 here: https://helpx.adobe.com/photoshop/kb/troubleshoot-gpu-graphics-card.html 

Photoshop uses the GPU for actual data processing, and the result returned to Photoshop for further processing. It's not a simple one-way downstream flow, like it is in simpler applications. You can't send data to one GPU and get it back from the other. There can only be one GPU in this equation.

Second, your system drive is about to fill up. 200 GB free space for the Photoshop scratch disk should not give immediate problems, but this quickly fills up in actual use, especially if you have many history states and/or big files and/or smart objects.

I'd recommend a good cleanup. A basic installation of operating system and a range of applications (including CC apps) should not take up much more than around 100-130 GB or so.

Now, there is an apparent bug that has hit some users, that is again GPU-related, and can eat up memory and disk space. And again, it seems to mostly affect systems with an integrated GPU that doesn't have its own VRAM, but instead uses shared system memory.

Normally, the GPU will use available memory up to around 85-90%, and then level out and reuse/recycle. But in these problematic cases, it eats up shared system memory, apparently unchecked, and then starts filling up the system pagefile. This will choke the whole system and bring it to a halt. 

A lot of users have come back and reported that a complete reset of Photoshop preferences has fixed this problem. That means not just clicking "reset", but physically moving the whole Photoshop 2025 Settings folder so a new one can be built. Preferences contain much more than your own user settings, it's the whole application configuration. Removing the folder returns the application to clean out-of-the-box factory state. It's here: Users > Your name > Appdata > Roaming > Adobe. Move it to the desktop for backup.

[kirkr5689]

D Fosse

Thank you for detailed  recommendations .       But the trues  is I had same slow behaviour on my desktop with a single videocard  and a hole separate SSD disk as a scratch disk for Photoshop + 16 core CPU .