Wednesday, January 25, 2006

Fun with eBay lenses

I'll need to add a couple of pictures to this post to illustrate, but I just received a lens I purchased on eBay. It's a well-used, manual-focus Vivitar 70-150 "Macro" zoom. I put Macro in quotes because it doesn't appear that this lens gets anywhere near the range of true macro 1:1 magnification. The closest focus distance is a couple of feet.

It's kind of an interesting challenge using a manual lens on the d50. Obviously, the lens is manual focus, but apparently because the d50 also lacks some mechanical linkage to read aperture information, the camera can't set the aperture either, so only the fully Manual mode really works.

So, I end up setting the aperture on the lens, the shutter speed with the camera, and figuring the exposure by taking a test shot and adjusting based on what the histogram shows. I got a couple of decent pictures of Jeremy the Attack Cockatoo before he got bored and tried to eat me.

It appears that this lens, at closest focus, gives about a 19cm wide field of view, as opposed to the 17cm I get with the 18-55 lens. Not exactly a "macro" zoom. I wonder if the fact that the lens rattles when I shake it has anything to do with that? Maybe there's supposed to be some additional extension at the end of the range, or something? I may just take it apart and see what I can do.

Thursday, January 12, 2006

On the subject of camera lenses

From an email I sent to a friend. The question at issue revolves around me getting my first digital camera with interchangeable lenses (a Nikon d50). The problem with having a choice of lenses is...needing to make a choice.

I've been thinking about the "how do I know what lenses I need?" question lately...

I was reading online that the conventional wisdom holds that the vast majority of pictures taken with a zoom lens are taken at either the minimum or the maximum focal length. So, I decided to check my own pictures and see if that's true. I found this program online called jhead, which will dump the exposure info out of digital camera JPEG files.I ran my entire iPhoto library through it, and analyzed the results with a Perl script.

I found out some interesting things about my picture taking habits.

Looking at the data for the E-10, which is the camera that I've taken the most pictures with, the distribution of zoom focal lengths look like this. To convert these from the E-10's smaller sensor size to the equivalent for 35mm field of view, you'd need to multiply by about 4.

focal # of pictures
9.0mm 1352
10.0mm 70
11.0mm 57
12.0mm 51
13.0mm 39
14.0mm 43
15.0mm 50
16.0mm 34
17.0mm 103
18.0mm 42
19.0mm 41
20.0mm 49
21.0mm 15
22.0mm 27
23.0mm 11
24.0mm 25
25.0mm 8
26.0mm 35
27.0mm 16
28.0mm 16
29.0mm 15
30.0mm 16
31.0mm 22
32.0mm 34
34.0mm 21
36.0mm 488

The conventional wisdom is confirmed, I guess. It's kind of fascinating to me that it's as lopsided as it is in favor of wide-angle though. I mean, I suspected that would be the case, but I didn't expect that it'd be so extreme.

It also interesting that there's that peak at 17mm (68mm equiv). Unfortunately, iPhoto won't let me search by focal length, but a quick visual scan through the library shows that most of these are relatively close-up shots of people's faces.

So based on the data, what *I* really need is one wide angle zoom lens, one portrait taking lens, which can probably be a non-zoom lens, and one telephoto zoom. Since the E-10 had neither a truly wide-angle or a truly high-magnification telephoto, it's not entirely clear what actual range I need on either end of the scale.

On the wide end I think the decision is easier. I decided to just get the widest wide-angle zoom I could find, which is how I ended up with my 10-20mm (15-30 35mm eq) zoom. So far, that's working out pretty well for me. And now I can shoot a 180 degree panorama in two shots, which is pretty cool...

For portraits, a 50mm lens is pretty close to the 45mm lens my data says I'd want. I'd just have to step a little farther away. 50mm being the "standard" length for 35mm lenses, the basic Nikon 50mm f/1.8 lens is relatively inexpensive at $100 or so. Now, I do have that range covered with my existing zoom lens, but the fixed lens gathers way more light at f/1.8 than the zoom does at its maximum f/5.6 - doing the calculation, that's about 9 times as much light, which will make all the difference in whether I need to use a flash or if I can use available light.

On the telephoto end, I'm at a bit of a loss. I wasn't very happy with the limited telephoto on the E-10, so I'm pretty sure I'll need something considerably longer than the 17-55 lens that came with the d50, which isn't even as good as that. But how far do I need to reach? I don't think I want a lens that absolutely requires the use of a tripod for every shot, and it would be pure insanity to pay over $1,000 for an optically stabilized (VR in Nikon-ese) lens.

One interesting (but not surprising) thing is that almost all of my (semi-Macro) flower pictures are at the far end of the E-10's zoom, as well. They look pretty good at that magnification, so the equivalent focal length on the d50 (which would be about 90mm)would be a good thing to have.

I should just get the 50mm lens, I guess, and maybe get a cheap telephoto zoom and explore what range I need before plunking down the money on a "serious" telephoto lens.