Drum Scans - What to order?

[Doug Dolde]

West Coast Imaging addresses this on their website:

What's the difference between an 8-bit scan and a 16-bit scan, technically speaking?
An 8-bit per channel file uses 256 definable tones in each R, G, and B channel. This creates a file that can define 16.7 million unique colors. The human eye can only see about 10 million colors, and tonal differences of 1%, which is why 8-bit files from film have been the industry standard since the beginning of digital imaging. A 16-bit per channel file uses 65,536 definable tones in each R, G, and B channel. This creates a file that can define 281 trillion unique colors.

When do you recommend ordering a 16-bit scan versus an 8-bit scan?
That is up to you to decide. When we use digital cameras, we usually use 16-bit files to get the most out of CMOS or CCD Sensors. With a drum scanner and photomultiplier tubes, our experience tells us that 16-bit film scans on the Tango are generally overkill, and will only cost more and take more time to work on in Photoshop. This may not be true of other scanners.

We've made tens of thousands of prints from 8-bit Tango Scans, without the need for 16-bit, with rare exceptions. Of course, the Tango is perfectly capable of making excellent 16 bit scans--but your car is probably capable of speeds over 100mph, but do you need to drive that fast in your daily commute? The choice is up to you, and we are happy to provide you with what you decide fits your needs.

[Ed Richards]

> This creates a file that can define 281 trillion unique colors.

Only if you count different brightness levels as different colors. This is a bigger issue with 8 bit - those bits have to have color and brightness data. That said, almost all printers are 8 bit, so unless you do some manipulation in Photoshop or the like, 8 bit is all you are ever going to see on paper. But every edit introduces rounding errors, so if you like to tweak your files with lots of little changes, your 8 bit histogram is going to look like a comb. The memory issue is very real with large format - you may have to step back to 8 bit to edit the file in Windows, with its 2 gig limits. (Boy, remember with 640K was the limit? Or 8k if you are really old.)

[julian_4860]

There's a difference between BW and Colour here. Can't remember the mathematical reason, but with an 8 bit BW scan, after you've made a few curves/levels moves you start messing up the tonality. You can see the 'toothcomb' from hell effect in the histo and this often translates to the print. With colour, for some reason, although you can sometimes see it in the histo it rarely transfers to the print. I always get 16bit scans for both BW and colour. But for colour shooters, who don't do big layers or manipulation of curves 8 bit is normally ok.

[Ben Diss]

This being the case, why shouldn't I just order the 8 bit scan, load it into CS2 and convert it to 16 bit for editing?

-Ben

[julian_4860]

because you can't just make up data. when you convert in PS, PS interpolates i.e. makes a best guess

[Brian Ellis]

A histogram can look pretty bad and you can still end up with a very respectable print. So you might be able to save $120 and get good prints even from an 8 bit scan followed by some editing. But then again maybe not. I suggested getting 16 bit files because you said these were your prized photographs. Why take a chance on ending up with less than optimum results on your prized photographs to save $120? Having a 16 bit file isn't a guarantee of anything but it sure gives you a lot more room within which to work before editing starts to adversely affect the print.

[Rick Russell]

As a newbie to large format, I was faced with the same conundrum. Initially I contacted a local photograher who has a business optimizing (i.e. Photoshop) and printing digital files. He spent a considerable amount of time with me strongly suggesting that I obtain as large as practical a scan at 16 bits. I then researched the various scanning services and settled on West Coast Imaging. In my discussions with them they advised a 300mb, 8 bit scan. Notwithstanding their advice, which was based on their experience with similar queries, I purchased a 600mb, 16 bit scan. After all, this was my first prized shot with my new 4x5 set up. I've received the scan back, and am told by the local photographer who will optimize and print that a.) West Coast Imaging did great work on my scan, and b.) given the importance to me of the shot, I did the right thing in purchasing the best quality scan reasonably available. I will have the finished print back in a few days, and am very excited by the prospects of having a great finished product which I will likely always cherish.

[Ben Diss]

OK, 16 bit it is. I just Fedex'd the order. Thanks everyone for the advice.

-Ben

[neil poulsen]

Why do them all at once. Try one at 48 bit (16 bits each channel) and the same one at 24 bit (8 bits each channel) and compare. Or, try one at 24 bits and see how it turns out. If you like the quality move on. If not, you haven't lost that much in expense.

Also, they're being done on a Tango. Tango scans come at a premium. Consider using someone with a scanner that isn't so expensive. You can always have an image scanned again, if it doesn't work. It might be more expensive if you don't like the lesser scan. But if it works, you've saved quite a bit.

I'm wondering if a 48 bit scan on a different, but less expensive, scanner is better than the 24 bit scan on a Tango.

[Michael Gordon]

I'm pretty late to the discussion, but the benefits of 16-bit scans are best realized with difficult-to-scan or contrasty negs/chromes , and images with banding potential (like those with graduated skies, for instance). 16-bit is otherwise overkill. As Brian Ellis points out, and a combed histogram does not necessarily equate to a bad print.

www.mgordonphotography.com