In a few months (late August), I’m planning on heading to Yellowstone National Park for a week’s worth of outdoor recreation and, I hope, many opportunities for photography in one of the most beautiful parts of the U.S. Since this is the first major photographic excursion I’ve gone on with a DSLR instead of film, I’ve been putting some thought into the contents of my gear bag.

At the moment I haven’t decided whether or not I’ll be bringing a laptop with me on the trip. If I decide to forgo a computer, I’ll either need to buy a lot more CF capacity than I have now, or get something to download the cards onto when they get full.

The price per GB on CF cards varies based on the speed of the card and the total capacity, with larger cards generally costing more then the older, smaller-capacity cards. The best deals currently going seem to be on the 100x (15MB/s) and 133x (20MB/s) cards, with a significant premium for the 266x (40MB/s) and faster UDMA varieties.

I found a 4GB 133x Kingston card for $15, and an 8GB 133x for $25, both at Adorama, and the latter with free shipping. That works out to around $3.13/GB — not too shabby, but not exactly disposably cheap.

It’s more interesting to consider the cost on a per-frame basis: each click of my Minolta Maxxum 7D’s shutter (when in RAW mode) consumes about 8.6MB, so if I were to use memory cards the same way I used to use film — treating it as a consumable, at least for the purpose of my trip — I’d be paying about 2.6 cents per image. By comparison, bulk-loaded Kodak Portra (my color film of choice) is around 3.3 cents per image, and that’s just for the stock, neglecting processing costs and any waste.

I knew digital photography was cheap, at least in terms of running costs, but that surprised me. CF cards are so inexpensive today that I could use them not only for in-camera storage but also as my archive copy, and I’d still come out ahead.

In terms of ‘film rolls,’ which is still a unit that I find myself thinking in, each 4GB card holds about 465 images or 13 35-exposure rolls. (I never shoot more than 35 frames on a roll of film, because I store them in binder pages that take 5-frame strips. Nothing more annoying than having one or two extra frames at the end of a roll that don’t fit into the binder page, forcing you to waste a second one.) If I were planning on taking my film camera, I’d probably bring 20 or 25 rolls, so I think two 4GB cards will probably do the trick.

Of course, I’ll probably take many more photos with a digital than I would with film, so it makes sense to budget more. It’s an open question in my mind whether I’ll really end up with more ‘keepers’ after the first cut than I would with film; in other words, do all the additional shots I take when I’m shooting digital actually amount to more good images, or do they just decrease the S/N ratio? One of my goals is to try and figure that out.