Best Mac Studio for Photoshop?

I think the base M2 Max Mac Studio, with enough memory and storage, should work fine for Photoshop. The problem with upgrading the Mac Studio to the M2 Ultra is that despite the fact that you spend $2000 to add CPU and GPU cores, Photoshop is not going to do very much with them, compared to other software. The additional cores mostly benefit video editing and 3D. Lightroom Classic can use extra cores to build previews or export files in parallel, but of course in Photoshop there aren’t many parallel or background tasks to throw unused cores at when you only have one or two files open.

…file size often reaches 3 MB.

By @steverap1

I am guessing you meant 3GB? Because raw files from current Sony bodies are much larger than 3MB. If your files do get to be 3GB, 64GB Unified Memory sounds like a good idea. One way to answer that question is to look at your current memory usage. When you edit a big file with Photoshop on your iMac, what is the Memory Pressure reading in Activity Monitor, Memory tab? For example, if your current iMac has 64GB RAM and when you edit a big file, Memory Pressure is always green, then you have no need to pay for more memory, because the macOS memory system (real memory + compressed memory + swap file) is able to handle all demands immediately. But if Memory Pressure is frequently orange or red at 64GB, then 96GB would be a good idea in your next Mac.

But the size of the Photoshop scratch disk will also be important. On your iMac, how much free space temporarily disappears on your assigned Photoshop scratch disk when you edit one of those files, and will there be room for that amount if you order 2TB internal storage? The high speed of Mac Studio internal storage makes it ideal for Photoshop scratch disk use, although it is expensive to upgrade it. Or do you already use a fast external SSD as a Photoshop scratch disk?

I use an a7r V, and often 3 or 4 files stitched, so normal routine pixel sizes for me are 10 000 - 15 000 pixels long side.

I'm on Windows, so can't compare directly. But CPU and RAM aren't critical for Photoshop. An 8 core CPU and 32 GB is plenty enough to handle these file sizes. Everything here is snappy and instant, even with many files open.

The critical components are the GPU and the scratch disk.

You need a decent and recent GPU, and as much fast NVMe disk space as you can get. I'd say 4 TB. You'll need a lot of space for the scratch disk, in addition to the system drive. The PCIe 4.0 interface is insanely fast, so that the scratch disk is not the bottleneck it once was. Hence the much reduced significance of RAM.

And then you can use spinning drives for long term storage.

Now, there is one special consideration for Apple silicon: it has an integrated GPU, which doesn't have dedicated VRAM - it uses shared system memory. Make no mistake, the GPU will eat up a lot of memory. So for Apple silicon, double the amount of RAM you would normally need. In other words, go 64.

On the Lightroom forum, there is a benchmark thread for GPU performance with Denoise. I use an RTX 4060Ti, which should probably be comparable to a basic M2. It Denoises a 60 MP file in a little over 20 seconds, which for all practical purposes is excellent. Even the most expensive RTX models can't squeeze that below 10 seconds.

If you can afford it @steverap1 go big or go home. Never skimp on GPU or CPU cores. Storage is cheap and externals are a great option for long-term storage and backups.