Focal Length and Compression

It's been awhile since I've been writing here.  This isn't because I haven't taken any pictures—it's because I have little time in my personal life to write much of anything, to say nothing of a photography blog.

However, I recently acquired a Nikkor 400mm f/5.6 AI-S and 85mm f/1.8 (AI'd).  Manual focus isn't everyone's thing, but I have enjoyed it a fair amount, and these are focal lengths of some interest to me, and help to illustrate how the longer focal length tends to "compress" a scene.

Here's a picture from the 85:

Fire hydrant?  85mm f/2.8, 1/5000s @ ISO 400

While they're not super obvious, there are clearly buildings in the background some distance away.  A somewhat equivalent picture from the 400:

400mm f/5.6, 1/1600s @ ISO 800

I did not take the most extreme care to ensure that the scenes were identical, but hopefully the compression is fairly obvious.  The background "feels" so much closer in this image than it does in the previous.  This is due to the compression induced by the focal length.  What this means is that the longer focal length (i.e., telephoto lens) tends to bring the background closer while the shorter focal length (i.e., wider angle) will present a scene with greater depth.


And just to make you jealous, a moon shot from the 400; it's cropped, run through unsharp, and has been color corrected some:

400mm f/8, 1/1000s @ 800 ISO; hand-held

Glut of Iceland

I've uploaded a lot of pictures from Iceland, but I've not yet done any technical work on any of the ones of interest: check them out.

I'll hope to have some commentary here eventually. I will say that the d7000 earned its stripes here, and the 70-300 was a good tool to have for some of the wildlife shooting. Continuous AF and reasonably snappy AF-S motor did a good job on several different shots.

The 28mm was the most commonly used lens on the trip; I was repeatedly disappointed that I didn't have anything wider, but I made do well enough with what was there.

Upcoming trip

I'm going to be in Iceland soon, and hopefully once I return I can provide some interesting pictures and/or technique observations. The past months have been increasingly busy, and they don't show any signs of slowing down.

More Megapixels isn't always Better

Just like processor speeds were the catch-all number used to sell computers in the late 90s and early 2000s, megapixels are the hot number in many camera advertisements. This seems to have cooled down some recently with the gradual deceleration of sensor sizes; the lack of new gigantic sensors means that other distinguishing features need to be used to differentiate competition.

There are several practical consequences to more megapixels, and many of them are bad, at least if you're not making larger prints. (Six megapixels will get you very clean 8x10 prints.)

For example, pixel density can be a barrier to relative sharpness. The resolution of a lens is finite, even though it's continuous, and when you exceed the limit of resolution on the glass, you'll find that the details get a little more muddy. (So for example, my 50mm f/1.8 AF-D still shines on the d7000, but the 28mm f/3.5 AI-S shows its age.)

Another issue with increased pixel density is that the camera is more sensitive to your body movement. While this is usually more obvious with longer focal lengths, I've noticed in my recent 10MP bump-up that it's harder to get equivalent sharpness with the same shutter speed. This makes sense, since more samples means a magnified view relative to a smaller pixel density. In essence it's like putting a magnifying glass on the image: you're bound to see things in higher magnification than you would see otherwise.

This sort of issue is made worse at longer focal lengths. I was pleasantly surprised by the sharpness of the AF-S f/4-5.6 55-200mm lens when I got it, and the 18-200 was pretty much the same. But the 70-300 at equivalent focal lengths is often blurry at the same shutter speeds.

This is one of the more immediate things I noticed when I started using the d7000: it takes a steadier hand than I'm used to, and I'm sure part of it has to do with those extra megapixels crowding that sensor. On the plus side, though, it definitely does allow for more spectacular shots when you need the center of frame just so.

Another View of Polaris

I meant to post this quite some time ago, but as it happens, my schedule and mind aren't always conducive:

This was my second effort at playing with the intervalometer. This time I didn't shoot RAW because of how long it took to do the batch conversion (nearly 8 hours on my netbook; and yes, I know I shouldn't use a netbook for that purpose).

This time it was the 50mm f/1.8 at f/3.5, ISO 1250, 15-second exposures. White balance was set at 3030K in camera to provide bluer affect and mitigate some of the warming tones from light pollution. One picture taken every 30s from midnight to 5 AM.

Again, I kept Polaris in view, but this time shifted down slightly. The more limited field of view is less satisfying than the wider angle, although the detail is sharper. I'll probably try another using the 28mm f/3.5 at 3.5 to see if it is any good.

I haven't had much time since then to work with the intervalometer, but I'm curious to see how a smaller field of view might work with a longer lens like the 70–300 VRII.