I'm wallowing in confusion and unable to get answers even from the sources in questions - Kodak and Iris/Scitex - so I thought I'd try this forum to see if anyone has a helpful real life answer for me.

Conventional wisdom is that a 35 mm transparency can only be blown up to 11x14" in traditional photo printing. Beyond that you risk softness. This is true enough in my experience.

However, when I consider the Iris (or Giclee) process, I enter murky water. Iris prints at 300 dpi (although effective resolution - what it appears as is touted as 1800). Using the 300 dpi output as the basis and using a photo cd scan at its highest resolution of 2048x3072 pixels.....what is my maximum output size while retaining crisp results?

Also, I could go to 2 1/4" film and use the Photo CD Pro scans @ 4096x6144 - which is still over double the resolution (2000x2000) of one of the latest 'high end' digital cameras costing $20,000 just for the back. So, as a subsidiary question, if I'm not concerned about convience, but strictly with quality, am I correct in reasoning that I'm still getting 'better', as in more actual image information, with my traditional film based photographic system combined with the Photo CD scan than with a new digital camera set up?

Help if you can. Thanks

-- Thomas Forsythe (strawng@xpressweb.com), June 22, 1998

Answers

I don't have a definitive, closed-form answer for you, but the PhotoCD process seems to do an excellent job of extracting all the available information from the film, at least from a resolution standpoint. In fact, I've heard some say that they feel they can get *larger* blow-ups digitally from PCD than from the film, because the PCD image processing does a good job of dropping out the film grain, without overly disturbing object edges. Thus, if you're about happy with 11x14 prints from 35mm film, you'll probably be about as happy (or unhappy) with the same size from PhotoCD. PhotoCD Pro is probably overkill for 35mm, although it's a great way to do lens tests! - The resolution is high enough that you can see every speck of chromatic aberration, coma, etc on the highest-resolution film. (Such as Kodak Royal Gold 25)

The scanning backs for 2 1/4 film cameras probably produce the highest resolution, but there's a lot of variation between them.

As a side note, one important difference with a PhotoCD approach is that you can increase the *apparent* sharpness quite a bit by playing with unsharp masking in Photoshop to enhance the edges. The trick is to get just the right amount: Too much and fine detail gets blobby, and you develop "halos" around high-contrast edges. Nonetheless, properly done unsharp masking makes a HUGE difference in how sharp a picture looks, compared to a conventional optical print.

-- Dave Etchells (web@imaging-resource.com), July 17, 1998.