I had hopes. Oh well.
I’ve been using Pentax K-Mount lenses since I received my first SLR camera. That camera is a Pentax K-1000 35mm film camera. It reminds me a bit of the early versions of Linux. The camera itself gives you just enough information to take a picture, but you have to be conscious of just about every aspect of what the camera is doing to get something interesting captured on film. Manual everything. Exposure, aperture, focus, film advance, well, OK there isn’t much left is there? The one thing that the camera had specifically built in was a light meter with a floating needle that would tell you if you had a film speed, shutter speed and aperture combination that would take a picture that could be developed. You could be pointing at a grey card, or a sunset, and the meter would move up or down as you adjusted other characteristics of the camera.
I received the camera with a basic 50mm f2.0 ‘M’ lens. It seems like a match made in heaven. The lens does not have any contacts to tell the camera what it’s capabilities are, allow the camera to adjust the aperture, much less automate the camera focus. Then again as you adjusted the aperture a lever would let the camera know what you had the f-stop set at. Without it, metering is pretty much useless. And while the lens is fully manual, none of my automated lenses, have an f-stop rating that comes close to that 2.0.
Now don’t get me wrong. Having an automated lens isn’t a requirement for taking great pictures. But there are a lot of situations where you want to be able to keep your attention ons something other than every aspect of what the camera is doing, and perhaps pay attention to the subject, or who knows, perhaps be aware of the oncoming car you’re shooting, so you can step out of the way at the right moment. OK, for most of us the advantage is to be able to compose our shot, take the picture, and move on. We might be interested in adjusting the shutter speed to address the rapidly moving kids. Or perhaps we are interested in setting the aperture to give us a better depth of field. But beyond that we’re usually OK with whatever the camera selects for the alternative.
And there are conditions where we want to be able to get as much light as possible into the camera. There are lenses available for cameras that are identified as being a f1.2 lens, or possibly f1:1.2. Most zoom lenses give you a maximum aperture of f4.5 or in some of the more expensive lenses, f3.5, but only at certain focal lengths. At ‘longer’ lengths you might only get a f5.6 aperture. A quick way to understand what this ratio means, is that for a unit of light to reach the film or sensor, the f-stop identifies how many units of light need to hit the front of the lens from what you are trying to take a picture of.
Essentially there are four factors in getting an image on the sensor, besides focus. The sensitivity of the sensor, The amount of light available, The time that the shutter is open, and the amount of light that is passed through the lens. Increasing the sensitivity of the sensor introduces ‘grain’ into the image. It may also be presenting noise of other sorts in digital photography. CCDs don’t really care whether the charge was built or removed by light in the wavelengths we see in, or in some other energetic spectrum.
We have a limited amount of control over the amount of light available. Outside, at night, in rural Montana, you may have nothing but the light of the stars above you available. I suppose that’s true of daylight as well, though the star involved there is a bit closer. You can add illumination to the situation, set up a huge floodlight, or gather a bunch of cars and turn on their headlights, but for the most part you will only get a small change in the overall lighting. Note that using a camera flash doesn’t do you all that much good outdoors, unless the setting is sufficiently similar to being indoors, as to not matter. Indoors, you probably have more control over the amount of light available, but even with that you are only going to get so much before people complain about it being too bright. The usual solution is to add a camera flash, but again too much light can bother people.
So, in places where you can’t increase the amount of light available, you start playing around with shutter speed. However you have to be careful here as well. The longer the camera shutter is open, the more likely it is that the camera or subject will move. The old, very old, way of solving this problem was to physically clamp people into place. If it looks like people are stiff and wooden in an old time picture, it’s probably because of the clamps, buckles, and related constraints, all cleverly hidden behind the subject, but generally ensuring that not even a finger moves during the time the shutter is open. The film process available at the time would often require that the camera be open for minutes at a time, compared to the fractions of a second we have been seeing for some time. The cameras also were mounted on as stable of a platform as the photographer could find. If he could fasten it to the floor, he would. Now-a-days we use lightweight tripods, or bean bags to hold the camera stable while the lens is open.
Finally we have some control over how much light can get through the lens. If you buy an SLR today, it’s almost a guarantee that you will get a zoom lens with the camera. It’s a very flexible piece of equipment, and generally works well. That’s not to say that the fixed focal length lenses don’t have their advantages. They do. The mechanics of bending light to change the focal length of a lens mean that there are more things within the lens that present an obstacle to light passing through the lens. It ‘narrows’ or reduces the maximum f-stop, which means less light gets to the sensor. As a result you see zoom lenses with f3.5, f4, f4.5 or worse maximum apertures. Fixed focal length lenses on the other hand don’t have the same arrangement of parts in them. Usually they have a barrel that is turned in and out to change the focus, and an iris that allows you to narrow down the amount of light getting through the lens. There is usually a second lens close to the sensor, but not a lot otherwise. Much more of the light can get through. The limiting factor is usually how much glass is actually involved in the lens. For a 50 mm lens (focal length) the range of maximum apertures range from a low cost f2 lens, to much higher cost f1.4 lenses. It is not unusual for the higher cost lenses to be more expensive than the camera they are mounted on. This is sometimes called ‘Good Glass.’
So, I’ve got this 50 mm lens that came with my K-1000. Can I use it? Actually yes I can, but there are a few limitations. If I pull out the K-1000, I have to use film. Theoretically I could replace the film with a digital sensor, but the camera body itself isn’t really designed for that, and it would be a lot of work I don’t really want to do on that camera. So the next question is can I use it on any of my other cameras? And the answer is a qualified yes. The first camera I would try this on is my K100D dslr. For the Pentax line, this is the digital equivalent of the K-1000 so far as the camera is a starter camera. And the 50mm lens does mate up to the camera. However it’s not nearly as good of a match as I would like.
The camera itself does not use the lever from the lens to let the camera know what the aperture you’ve selected is, and also does not have the ability to switch the lens from view, or wide open, mode to the selected aperture. So you are stuck with wide open when taking pictures with the lens. That’s not altogether bad, but when taking photos indoors, it can easily overwhelm the sensor. But it is a lens, and allows you to focus, and if all goes well, you can take some very good pictures.
I’m going to try something a little bit different though. I’m going to pick up a low cost Pentax SMC-A lens. If all goes well, that lens will not have auto-focus, but the amount of light coming in should be helpful in indoor photography situations. We shall see.
I have one other lens that I’m interested in getting. Thought I had ordered as a matter of fact, but hadn’t. That’s an 18-200mm zoom lens to go on the K20D. Who knows though, I may switch up the lenses and camera bodies. We’ll see.
