View Full Version : DPI or DMAX?

matthew blais
1-Apr-2004, 10:51
Although this is not specific to LF, I do want to be able to scan my future negs and trannies from 4x5. So my question relates to the digital LF darkroom.

It's time to upgrade my AGFA Arcus 1200 as I'm tired of the slowness, intermittent recognition problems from my Mac G4 OSX.6 Jaguar via the scuzzi connect, and it's a "dinosauer" (sp?) at three years old.

I'm looking at two: Obviously the new Epson 4870, (as some have already commented on) and a Microtek Artixscan 1800f. Why that one? Well, it purports a DMAX of 4.8, (my pre-press guy at my commercial offset printer uses one and use to operate a Tango DS). However, is the dpi a drawback? It lists a 3,600 x 1,800 dpi, (which my simple math from my simple mind) interprets this to mean if my target dpi is 300, then the largest optimized scan I can do is 6" x 12".

Whereby the Epson (DMAX - 3.8) lists a dpi of 4800 x 9600, which would enable (same specs) a scan of 16 x 32.

1) Am I calculating wrong? 2) And what, IYMVO, is more critical if you want to scan to a decent 11 x 14, maybe a bit larger? 3) Is there another unit that has both high dpi and DMAX? (Flatbed type only)

I certainly don't expect a drum scan quality, and I know many here have listed the 3200 and even 2450 Epsons as their current scanners. There is a price difference of $400 between the two, with the Epson being less, but is not a large factor. I would use it for my business as well.

Thanks to all.

Guy Tal
1-Apr-2004, 11:34
Assuming a 4.5" x 3.5" actual area scanned at 1800dpi will give you 8100x6300 pixels (or ~51 megapixel for those who like to compare with digicams). Printed at 300dpi you can make a 21x17" print with no interpolation. A good clean scan will easily interpolate to much larger sizes.


Guy Tal
1-Apr-2004, 11:35
Oops.. that's 21x27"... with no interpolation.

Leonard Evens
1-Apr-2004, 13:31
You should be able to scan the whole 4 x 5 film format, which is just about 95 x 120 mm. 1800 ppi is 1800/25.4 ~ 70.87 pixels per mm. That would produce an image about 6732 x 8504 pixels. Dividing each by 300, which is a commonly recommended ppi to send a printer, would yield a 22.4 x 28 inch print.

However, you should be skeptical about both the quoted dpi (really ppi) for the scanner and the quoted dmax.

The first figure is just the scanning resolution which tells you how many pixel samples are collected by the scanner per inch. It doesn't tell you how well the scanner resolves fine detail.

No scanner is perfect, but the Epson scanners are known to depart substantially from what a perfect scanner would deliver. Estimates are that it resolves detail about as well as a perfect 2000 ppi scanner, remembering of course that no such perfect scanner exists. That means that although it would give you enough pixels to send an inkjet printer for very large prints, those prints would show degradation when examined close up. Whatever resolution you scanned at, you would probably rescale to at most 2000 ppi before printing anyway.

I don't know how close the Microtek gets to a perfect 1800 ppi scanner, but it may be proportionately closer. If it delivers as much as a perfect 1600 ppi scanner, that may suffice, but I doubt that it does so.

The figures given for dmax are often quite misleading. The 4.8 figure is almost certainly a figure calculated on the basis of its having 16 bits per channel. It is unlikely that the Microtek can actually handle a true dmax of 4.8. Epson could also claim a dmax of 4.8 since it also is a 16 bit per channel scanner. From the reports I've seen, their claimed dmax of 3.8 is probably fairly accurate.

Henry Ambrose
1-Apr-2004, 15:40
Ask your printer friend with the Microtek to scan a piece of your film. Since he is an accomplished operator you can see just how good that machine is. As others have written the manufacturers claims for DMAX are not to be believed. Resolution too for that matter. But, I think any of the scanners you mention will give you very nice 11X14s.

I've had several Agfa scanners in the past - Duo, Arcus, Duo T2500. The 2500 was pretty heavy-duty and had a very sharp optical system but not great DMAX. My current Epson 1680 beats the pants off the T2500 even though the Agfa gave sharper raw scans and has higher resolution figures.

Whatever you buy, do expect to perform some post scanning processing to get the best prints - you'll have to mess with your scans a bit.

tim atherton
1-Apr-2004, 17:26
Iv'e used the bigger Epson 1680 and the older smaller epson 3200 (?) by comparison I had some scan done on the Microtek 1800 and it did better than both of those. Generally sharper and better DMax than both (whatever the advertised rtange is...) - noticablly so.

And yes, you should be able to get close to a pritn just under 24x30 @ 300dpi scanning at 1800ppi. And with very good interpolation software like Photozoom/Zoomview (rather better than Genuine Fractals in my tests) easily print somewhat bigger.

matthew blais
1-Apr-2004, 21:20
Thanks to all for your input. I think I understand the whole size thing now... Tim, I never tried (or heard of for that matter) the Photozoom...Mfg. of this? I do have GF and haven't been overly impressed. And - glad to hear you have used the Microtek 1800 and noticed a difference. Now, is it worth the extra $400....?

Good idea to get my prepress guy to scan something, then someone with an Epson, & compare. But then it's subjective I suppose due to operators, if not the same.

Again-thanks, and if anything else out there under $1K that will perform as well or better, please post the results/info.

Frank Petronio
1-Apr-2004, 22:16
Nothing beats real world testing, as the way scanner specs are described is not consistent between manufacturers. Many people like their Epson 2450, 3200, and 4870 scanners - they are a good value for the money. I suspect that the next significant leap in quality would be with an Imacon, although perhaps that Microtek is really better than the Epson. But more people use Epsons, and being a sheep, I follow the crowd.

I favor working with a 360 dpi resolution for inkjet printing, as my superstition tells me that the printer works at this native resolution (not 300 dpi), and do my scanning and scaling at multiples of 2x, 4x, 8x, etc... from the scans made at the actual optical resolution of the Epson (either 1200 or 1600 dpi depending on the model). Scanning at 3600 or 4800 dpi just means the scanner is doing the interpolation and adding noise from heat and time.

There are a few old SCSI Agfas in my junk pile too. Epson has done a decent job with updates and their prices aren't bad, so I am now a loyal follower...

tim atherton
1-Apr-2004, 22:52
> Thanks to all for your input. I think I understand the whole size thing > now... Tim, I never tried (or heard of for that matter) the > Photozoom...Mfg. of this? I do have GF and haven't been overly impressed. > And - glad to hear you have used the Microtek 1800 and noticed a > difference. Now, is it worth the extra $400....?

if I get around to it will be for 8x10 so there aren't to many options in it's range

photozoom http://www.trulyphotomagic.com

of course the more expensive pro version is th ebetter one... mainly because it allows you to play with the perameters, especially their built in sharpening.

You can try it out with watermarks on everything

2-Apr-2004, 02:22
Scanners fall prey to specmanship, you really should ignore all numbers and get some scans done. What is often forgotten is the sharpness of the optics, the ability to hold the film flat, and the dof of the scanner. I've used a 1680, the new epson and have now bought a 120 film scanner (won't do lf of course) but the microtek 120tf blows the flatbeds away for sharpness. As to is the 400usd extra worth it... your final prints are only as good as the weakest link in the chain. Poor scans make any money you've spent on camera optics a waste. I'd even go as far as to say that for me, a 120 neg on a film scanner will produce a better print than a 5x4 on a cheap (under 2k) flatbed.

11-Aug-2004, 06:01
I have a rather poor Digital Camera. After my Nikon, I wanted a 'test' with the "digital camera" concept. Easy of use is very high, quality only gets really good with the higher priced digital camera's...

I've tested the Photozoom program.
I found out a few very nice things. The Pro version also has a Adpbe Photoshop Plugin. They also develop both Windows and Mac products almost simultaneously.
And they have some other pretty nice Digital Imagery Software (including ports to Mac).
www.trulyphotomagic.com (http://www.trulyphotomagic.com/)