How Much Ram for Digital Processing?

[Michael Heald]

Hello! With suggestions from folks, I've started getting a handle on what scanner and printer to upgrade to in order to obtain digital prints from 4x5 B&W negatives. Now, I'm trying to decide on the computer upgrade that such processing will require.

Currently, I'm using a P4 with 512 MB of RAM. I anticipate the maximum size that I'll print is 16x20. After recommendations, I read Scanning and Halftones by Blatner, et.al. For a 4x enlargement to 16x20 and 360 dpi printer output, a 4x5 should be scanned at a minimum of 1440 spi, if I understand the reasoning presented in the book and on this forum. My current computer setup handles 8 bit files at this resolution reasonably well.

However, when I jump up to 2400 spi, digital processing is very slow with my computer setup. I imagine it will slow down even further when/if I start processing 16 bit files. I am trying to decide if I need 1 Gig, 1.5 Gig, or 2 Gig of RAM.

So, aside from extra scanning resolution that might be needed to handle cropping of specific negatives, do folks find that there are differences in high quality 16x20 prints if the files comes from 1440 spi, 2400 spi, or even larger scans? Thank you and best regards.

Mike

[Bruce Watson]

I drum scan my 5x4 negatives, both B&W and color. My purpose is often for prints in the range of 10x enlargement. My file sizes end up being around 350MB and 1.0GB. I can write books about Photoshop being slow (I have plenty of time to write between operations ;-)

First things first, you do want 16 bit scans for B&W. Bite the bullet and do it. Well worth it if you do much of any manipulation because you don't have any color to hide behind. What you do will definitely show in the print.

What you want is enough memory available to Photoshop so that it doesn't have to swap to disk. This amount varies from version to version, but a general rule of thumb is about 5 times your scanned file size. Put another way, for best performance you want as much memory as your motherboard can handle.

To carry the performance theme a bit farther, if Photoshop is going to swap to disk (and no matter what you do it will on occasion), you want it to swap to a spindle other than the spindle used by the OS. So you want a second (fast) hard drive mostly used for Photoshop swap space.

More than that, you want to hit the various online Photoshop forums and dig through the archives looking for performance tips that are specific to your version of OS, and your version of PS.

[brian reed]

Hello Michael,
the best answer is to get as much ram that your motherboard will support. Are you using windows or Mac? PSCS2 will only support 1.7 gigs of ram with windows XP. However Windows XP Pro with service pak 2 will allow you to use a little over 3 gigs, if and only if you edit the boot ini file to turn on the 3 gig parameter. With Mac you can use 3 gigs of ram without doing anything special, so I'm told.
BR

[Mark Fisher]

My experience with B&W says that 16bit is a must. Anything less won't let do much in the way of tonal adjustments without seeing some posterization. If you want 16x20 images, that makes for a pretty big file and 2GB would probably be the minimum you should go with. I have 1.5GB and only go to about 12x15 and things really start to slow down especially if I create any layers.

[Ron Marshall]

I have 2 Gig and a second hard drive on a PC and most PS CS2 image manipulations are very fast with 16x20 at 360 dpi output equivalent.

[Mike Lewis]

I can't tell you about 16x20 print quality from different scan resolutions, but I can give you some computer performance info. I scan color 4x5 negatives and transparencies into 16-bit pixel depth files. These tend to be around 600 MB. I use Photoshop on an Apple Power Mac G4, fully populated with 2 GB of RAM. It isn't enough. Lately I've run the Apple's System Monitor program while editing files and have noticed that the CPUs are never pegged at 100%. However, I do fill up the RAM and the machine swaps files to disk, a lot. Yesterday I mowed my front yard while running a sharpening plug-in on an image file, mowed the side yard while it saved to disk, and mowed the back while the machine processed the image for printing.

I'm beginning to believe that in order to be productive with image files of this size one would need a machine that will address 4GB+ of RAM, and has some kind of RAID 0 storage array striped across three or more disks to use for Photoshop swap and image file storage. CPU type/speed is less relevant, as long as it and Photoshop can handle the RAM you need.

[Gregory Gomez]

This may not be relevant, but I do tech writing and desktop publishing for a living.

My Macintosh had only one gigabyte of RAM, and it was not enough to handle several programs simultaneously. When I increased it to 1.5 gigabytes, performance improved noticeably.

I would say that if you can afford 1.5 to 2.0 gigabytes, I would go with that RAM size.

I hope this helps.

[Marko]

Memory is cheap these days. Buy all you can fit, you can't get too much of it. Also, get a second hard disk and reserve it for Photoshop. A physical drive, not just a partition. That should speed things up when Photoshop starts writing to disk, especially on a PC.

Photoshop CS2 can effectively use 4GB of RAM. That's for images, the application itself needs some RAM to run, plus the memory for the OS, plus whatever else is running in the background. This means that even 8 GB of RAM would not be too much...

[Daniel Geiger]

For PS I use a Mac G5 with 3.5 GB RAM and it works ok. What I did notice is that 16 bit processing (particularly spotting with healing brush) is very slow, slower than on a file with twice as many pixels in 8 bit. It seems that it is not only file size, but the 16 bit cost some extra computational power. But as everybody else has said, go for 16 bit anyway.

On the PC, I have 3 GB with the 3GB boot-option (not for photoshop, but for 3D reconstruction software). On the fairly new Dell X dimension box, after I installed the additional RAM, the XP system profiler only recognized 2 GB. After some conversations in French with the computer, reseating RAM banks, restarting a few times etc., I checked available RAM in the 3D application (amira) and there it recognized the 3GB. It seems that XP-Pro can only count up to 2GB.

On the Mac, the buffer RAM in the HD seems to make a difference. I just fried the original 160 GB drive, and installed a 400 GB with 16 MB buffer RAM. All disk operations are noticeable faster.

[Marko]

What I did notice is that 16 bit processing (particularly spotting with healing brush) is very slow, slower than on a file with twice as many pixels in 8 bit. It seems that it is not only file size, but the 16 bit cost some extra computational power.

Daniel, that's 8-bit vs. 16-bit per channel. There are three channels (unless you're working in 16-bit grayscale). Each channel handles 256 levels in 8-bit and 65,536 levels in 16-bit.

In other words, the difference is not linear but exponential. A 16-bit channel contains not twice but 256 times the number of bits than the 8-bit one. And there's three of them, if you're in RGB and not grayscale. That's where the difference you're feeling is coming from.