Capitol dome

Nikon D7000, 28mm (28-200), 1/250, f/8, ISO 110

Last week we were inside the capitol in Topeka, so this week let’s step outside and play around with zooming for a minute.

These are among the first shots I took with a new toy: a Tamron 28-200mm zoom lens. For some time now I’d been working with a Nikkor 18-55mm zoom as my standard lens, the one I left attached to the Nikon D7000 (the more powerful of the two digital cameras I use regularly) for everyday use. However, I found myself somewhat dissatisfied with the limits of being able to zoom in only to 55mm. So at the recommendation of the good folks at Overland Photo Supply, I opted to take a chance on a brand I’d never tried before.

Thus far I’ve been quite pleased with the results. I took the shot at the top of this post at the lens’s widest focal length: 28mm. This allows me to capture the overall “lay of the land” but doesn’t give me a ton of detail on any one particular spot.

So my next shot is zoomed in to the other end of the lens’s limits: 200mm.

Nikon D7000, 200mm (28-200), 1/1250, f/5.6, ISO 400

Mind, I didn’t move my feet at all. The camera is no closer to the subject. All this took was a twist of the lens.

That’s the limit of optical zoom, the zooming that can be done with the lens itself. However, the file size allows for a considerable amount of digital zoom. Here’s how it works:

At its highest image quality levels, the D7000’s photos are 4928 pixels by 3264 pixels. That’s way bigger than anything we need for computer screen display, so as a rule of thumb I reduce image size to 1000 pixels along the longest edge before uploading to the blog. That cuts D7000 photos down to 1000 x 662 (or 662 x 1000 if it happens to be a vertical composition).

But what if I crop the image rather than reducing it? In Photoshop I can use the crop tool to cut out a tiny 1000 x 662 chunk out of the huge 4928 x 3264 picture. Thus I can make it look like I zoomed in with the lens even though what I’m actually doing is cropping down to a small chunk of a larger picture:

Nikon D7000, 200mm (28-200), 1/1250, f/5.6, ISO 400, cropped

Extra for intermediate and advanced photographers: though I’m pleased with the result (this is way more detail than I could ever have dreamed of if I’d been stuck at 28mm), I am a little annoyed at the camera’s exposure decisions. I put the D7000 on automatic exposure mode so I could concentrate exclusively on what I was doing with the lens. Usually auto mode works reasonably well, but here it made some odd decisions.

The 1/1250 shutter speed is way too fast for a subject that isn’t moving (indeed, that’s too fast even for most objects that are moving). I don’t want to dip below 1/200 in order to avoid camera shake problems at this focal length. Still ...

The shutter speed itself isn’t a problem, but to compensate for the speed the camera does some things I don’t want. It compensates for the tiny amount of light that gets through in 1/1250th of a second by opening the aperture all the way up to 5.6, narrowing the depth of field and making it harder to focus. It also cranked the ISO up to 400, which starts to add some graininess into the image.

In fairness to the camera, you do need to worry about the shutter speed with telephoto shots, because even tiny vibrations can cause camera motion blur. But on a bright, sunny day like this, if I’d had the camera in manual exposure mode I would have set the ISO at 100 and sacrificed at least some shutter speed in order to keep the f-stop narrower.