Canon T1i memory card choices from SanDisk

The (unofficial) Canon T1i Blog has a recent post regarding SDHC memory cards for the Canon T1i. Unfortunately, it lacks an indepth analysis; a point about card capacity can be misleading (they quoted large JPEGs, but not RAW shooting which will be of interest to the dedicated amateur). In this blog post I'll attempt to answer the question: Between rated speed and capacity, which is more important?

First the good news: The blog recommends the 20 MByte/sec SDHC Class 6 Extreme III 8 GB cards, which give a decent price to performance ratio, with a focus on maximum capacity, i.e., being able to store double the shots of a 4GB model. You could certainly do worse than shoot with those cards. However, they're slightly more expensive than my option, and you may not use all the space in any trip, which would cancel out the reason for buying the larger cards (keep in mind that, unlike lenses, memory cards are not a long-term investment).

The bad news: The blogger doesn't mention the rebates currently available. Adorama.com provides a PDF download on their site to mail in with barcodes from the packages of their three-packs, shaving nearly half the price off the two deals I'm going to look at. Of course, you don't need to buy from them if you don't want to; the rebate lists other qualifying e-tailers.

The ugly: There's more to consider than simply "bigger is better;" what's important to the photographer. Furthermore, simply pushing Class 6 without noticing the huge differences (advertised, not tested!) in data rate is giving incomplete guidance; yep, Extreme III is no guarantee of the best speed. No worries though: Here is...the rest of the story.

When I went to get SDHC cards for my own T1i, I wanted to balance speed and capacity against price. Speed is a priority for the movie mode (slow cards fill the camera's buffer, and when that's full, video recording ends until it's saved to the card) - a mode which, so far, I've not needed to use; instead, I've noticed the speed pays off when previewing pictures still on the camera body - it's fast enough that I can easily separate good shots from the bad, and delete them right off the camera. In fact, turning on the camera and getting Windows to recognize it is by far the longest part of the deal (and even that's just a few seconds).

How many shots can I take with a 4GB card?
Let's clear up a minor point of contention from that blog. Their quoted figure of 600 shots is just for the largest-size high quality JPEGs. This is good for most purposes, but if you want to print your photos, or do fancy stuff like correcting chromatic abberation introduced by your cheap-o 18-55mm EF-S kit lens, you'll want RAW.

The T1i estimates you'll get 127 shots in RAW + high quality JPEG mode with a factory-fresh SanDisk 4GB SDHC Class 6 Extreme III; the T1i manual estimates you'll get about 18 minutes of video (I believe that's the 720p HD mode, but don't quote me on it). Switching the camera to RAW only gives 163 shots estimated. We're talking about 15 Mbytes for RAW shooting (4752x3168), and about (this next figure is based off my own shooting experience) 20 Mbytes for RAW + high quality JPEG shots. The JPEGs I've found to be between 4 and 5 Mbytes; the RAWs account for the rest.

The "ultimate" SDHC Class 6 card would be an 8GB (or larger) Extreme III 30 MB/sec edition (recognizable by its red label, as opposed to the 20 MByte/sec version's flat shades), but that will cost you an arm and a leg. If you need that card, you certainly aren't in need of my guidance; you'll be making use of every last shot and still swapping cards, and using the fast speed to save time transferring their pictures to the PC (of course, users that need the space are probably using cameras that can use the larger, physically and bit-wise, Compact Flash format - which SanDisk feels already warrants an "Extreme IV" label, giving it a bump up from SDHC and it's not more expensive either; but it won't fit in the T1i we're discussing today, nor many of its cousins).

For the average user, paying as much for memory cards (which are quickly superceded by better, faster models) as for lenses makes no sense.

Pricing breakdown: How many dollars per gigabyte?
I wanted three cards (more on that at the end; see Conclusion). Here's the pricing off Adorama's Camera, with the rebates factored in (the rebates are linear, i.e. buying three cards gives you three rebates, and they can be stacked for each card):

SDHC Class 6 Extreme III, three 8 GB cards, 20 MByte/sec
99.95 / 24
4.16 dollars / gigabyte (24 gigabytes)

SDHC Class 6 Extreme III, three 4 GB cards, 30 MByte/sec
74.95 / 12 GB
6.25 dollars / gigabyte (12 gigabytes)

We're getting closer to the conclusion, don't worry! In terms of a straightforward dollar / gigabyte ratio, sure, the 20 MByte/second version wins. However, you see that your unit cost is lower; this holds for the three-pack by $15. Not gonna break the bank, but consider that the 12 GB cards are also faster than the 20 MByte/second ones, which are only 2/3 the speed of the 30 MByte/second cards.

Factor in that speed, and the price evens out.

Factor in a realistic working environment
Well, that's a bit messy. I haven't tried out the movie mode, which could be the definitive point - but I can say that the 30 MB/second edition will soak in data faster than the 20 MByte/sec cards can, so at best it doesn't change my analysis for the 20 MByte/sec edition. At worst, the 20 MByte/sec edition could prove too slow for shooting continuous videos.

What I can say is that 12 GB has proven enough for days of experimental shooting for me - I haven't even touched the final card. In a situation where I had to shoot a lot of pictures and didn't have quick access to a PC, I'd be very happy for all three cards. All things being equal, the double capacity of the 8 GB cards would finish this contest off. But the market has pushed the price of the 4GB cards down considerably; it's $15 less out of your pocket (after the rebate) and they're faster. This extra speed is very handy for a faster workflow.

Depending on your personal computer, you'll probably find that 20 MByte/sec is already fast enough for you - theoretically it'll load up those previews on your computer quicker than anything you're used to. If you're using a USB to miniUSB cable and USB 2.0 slots, you'll find that the data connection is wide enough (at 60 Mbytes/sec) not to be a bottleneck, and on a good computer they'll probably load at just about one second. I find that the 30 MByte/second card pause for loading the 5MB full-resolution JPEGs is just short enough to avoid being an annoyance. It lets me quick-flip between pictures and compare them - although the better practice would be to load each preview into its own separate window (i.e. Irfanview versus Windows Picture and Fax Viewer, Windows XP's image "preview" application).

Of course, all bets are off if you have a terrible old PC. On a 1.7 GHz Celeron with 1GB of RAM, it takes many seconds to load previews (and they're less easily flipped through as well).

Conclusion
Ultimately, I'm glad I paid less in total for the 4 GByte cards, and it's nice that they're faster. But smart workflow procedures (namely, loading each preview into its own window, and putting pictures onto a semi-modern hard drive for detailed work) should remove the speed advantage of the 30 GByte-second format for all purposes but possibly file transfers (2/3 speed is not likely to break your patience) and possibly movie shooting.

The question you need to ask, then, is: Am I going to need more than 127 pictures on each card? Answering that question will point you towards the answer.

Of course, if you're shooting lower-quality or lower-resolution shots, or not using RAW, by all means go with what's cheapest since shooting just the large, high-quality JPEGs will give you 600 shots, and the hobbyist shooter is not likely to need more than that. The T1i isn't fast enough in burst shooting to use that much quickly.

You could play a game of "egg consolidation" (all the eggs in fewer baskets) by going for two 20 MByte/sec cards, and you'd be saving money over my choice while still having 4GB more space, but I liked the three-card bundle better because the extra space wasn't really necessary. Turns out that's about exactly the right amount of storage for me - 3 cards will span me roughly three days of normal project shoots, and would do me well for one long, very tiring day-long shoot, something like being at the best theme park in the world (your choice; I'll pass, personally) from sunup to sundown.

If you're generally tethered to your home and just use a camera for short nature walks and local excursions, you might get by with just two cards if you want a baseline level of redundancy to avoid being unable to shoot for a while if one goes bad. You can invest the savings towards getting an efficient three-platter 1-terabyte hard drive! Even the savings from one card will cover a significant part of such an expense.

A final note about monitor resolution
Without consciously dividing the resolution, I noticed my 1600x1200 monitor shows roughly 1/9 of the photo when zoomed in all the way (and indeed it does, as the images are 4752x3168), so I can use the elevator scroll bars as if they only had three positions each and not miss any of the picture - in fact there's a little overlap which roughly covers for the loss to the Windows Taskbar and title bars. Nice! For this camera, that is the minimum monitor resolution you should be working on (caveats about lower DPI to save your eyes apply, however; I'm looking at roughly a 21" monitor size). Of course, 1920x1200 is the future, but that's another blog post, isn't it?