I’ve Moved!
November 20, 2008
So I’m sure that most people have noticed that the site has been offline for a few days. There’s a reason for that, which I will get to shortly. But first, let me just say this:
In fact, I am blogging at a new site I have just finished setting up: kennethhynek.net. A full explanation for the reasons behind the move can be found here
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That said, this is not the end of Time Immortal. My wife Grace has expressed interest in taking over blogging at this domain, and I am working to make sure that she gets set up here as soon as possible.
Also, my profound apologies for the modification to the site face; the move was not as seamless as I would have hoped, and many of the image files for this theme, and in the gallery, were corrupted during the course of their evacuation from my previous web host’s servers. Until such time as I have repaired them, I’ve put a clean-looking template in place of the previous one.
Update: for the purposes of further traffic shaping, new posts from kennethhynek.net will be excerpted below. Full articles can be read at the new blog.
DPReview now does lens reviews as well
January 29, 2008
This is a valuable service. The thing that I think a lot of people don’t realize about digital photography is that when one makes the transition between compact digital cameras and SLRs, one has to change one’s assumptions and considerations as far as what affects image quality is concerned.
If you think about film for a moment, O Reader, what ultimately affected the quality of any photograph was the lens in front of the film frame. Because a film compact and a film SLR both used, or could use, the same kind of 35 mm film, and indeed the same development processes, the only thing that varied when one made the jump between compact and SLR was lens glass quality.
This ceased to be the case with digital compact cameras, because unlike with film cameras, the size of sensor in a digital compact versus that of a digital SLR was vastly different — not only was the compact camera itself smaller, but its sensor was smaller as well. Common sensor sizes in compacts these days are 1/1.8″ or 1/2.5″ (i.e. somewhat smaller than the average pinky finger’s nail). Common sensor sizes in SLRs range somewhat, typically being somewhere between about 17.5 mm and 35 mm (and 35 mm sensors are rare birds indeed; only a handful of digital SLRs use “full frame” sensors, which are quite expensive to manufacture).
This introduced a bit of a problem in terms of making accurate quality comparisons between compacts and their larger brothers, SLRs. While both a compact sensor and an SLR sensor might sport, say, 8 megapixels of resolution, the smaller size of the compact sensor means that individually, each of its 8-ish million photosites is much smaller than its equivalent on the SLR sensor. That, in turn, means that each photosite in the compact is measurably less sensitive to light, and thus requires more electronic amplification in order to properly expose an image.
And electronic amplification also amplifies electronic noise.
As a general rule, this isn’t as much of a problem at low ISO settings — at ISO 50 or 100, an 8 megapixel compact sensor and an 8 megapixel SLR sensor will churn out an almost identical image. Ratchet the ISO up to 400, 800, or 1600, though, and only the SLR sensor will be producing images that have not lost an unreasonable amount of detail to noise and grain.
So when making the jump between digital compacts and SLRs, it’s not just the lens that contributes to image quality. The camera owner who upgrades will see a quality gain simply by virtue of the difference in sensor sizes, even when he or she is content to just use whatever “kit” lens comes with the new SLR.
Of course, once one has upgraded to an SLR, that’s not the end of the quality discussion. Unfortunately, because of the compact/SLR discrepancy, more and more of the general public seems to have lost touch with the simple fact that it is the glass of the camera’s lens that used to be the main determinant of image quality. But once one has begun to use an SLR camera, that again becomes a major consideration. The jump in image quality over that of a compact is nice, but it’s also only the tip of the iceberg — there is typically much, much more detail that the sensor can contribute to an image, provided that the glass in front of it is able to accurately resolve that detail.
Which is why lens reviews are useful.
It goes without saying that most people would think of, say, the Canon EOS 40D as being a superior camera to the Canon EOS 400D. That’s kind of true, in that the 40D gives the user tighter controls over the shooting parameters of the camera. But by the same token, it’s also not the whole truth. If I put an el-cheapo EF-S 18-55 mm IS lens in front of the 40D and a EF 24-70 L-series lens in front of the 400D, the pictures from the 400D will, as a general rule, turn out better (assuming that both cameras are being used by competent persons of approximately equal photographic skill), because the lens quality is so much higher.
So it’s nice that the photography resource that I tend to trust first is starting to review lenses. I’ve got my eye on more than a few different lenses at present, and it will be interesting to see how many of them make it onto the review site (and how they rate as a result).
Update: Wow, the EOS 350D (Rebel XT) has really dropped in price. I’d almost be tempted to pick up a second camera body.
