Hi John ( and to whomever else it may concern), I knew there was a couple of other things that I had wanted to mention as far as the autofocus was concerned, but I think they got caught up in the cobwebs upstairs. After a series of headslaps and a game of hockey, it all came tumbling down.
I am not sure if you are using a 300 2.8 or a 300 4.0 lens. As I had said before, the center focus spot on the EOS-1n (as well as an A2) has a cross biased sensor, in other words it can detect horizontal and vertical contrast delineations. The four other spots have vertical sensors, detecting only horizontal delineations. Here is the kicker. If the lens (or teleconverter-lens combo), have a maximum aperture of smaller than f2.8, the center spot becomes a sensor effectively only with horizontal sensors, or vertical delineation, which reduces the ability of the autofocus to a certain degree. If you are using a 300 f2.8, no problems, but as soon as you attach the teleconverter, you lose the cross biased sensor, defaulting to the vertical delineation. Although for the most part, a person shooting normal (non-train) objects, this problem is not a real problem, because of the many varied objects with lines and contrast all over them. But to us train photographers, it creates a definite situation where autofocus reliability, and promptness suffers, because of the relatively smooth and featureless noses (or sides) of locomotives. If you have the 300 f4.0, you never had the cross bias in the center anyway, and adding the 1.4X teleconverter brings you to f5.6, which is the limit of autofocus capabilities, and can enhance the problem, especially with headlight glare. The higher up on the pilot that the ditch lights are located, the worse the problem. Here is a perfect example. I bet if you go back over all you pictures shot with the EOS-1n, you will note that Santa Fe G.E. Red Warbonnets, are among your sharpest pictures, and SP AC4400's or SP C44-9W's are among your worst focused. (This is a little bit of a guess due to personal experience). The reasoning. The Santa Fe G.E. Red Warbonnets have a "noisy" nose logo, which is easy for the camera to focus on and track. On top of that, the ditch lights are below the anticlimber which causes less interference with the sensors when focusing on the logo. On the SD75M's, the ditch lights are above the anticlimber, and the pictures have a tendency to be a little softer. Its worse on the 8200 series, and the GP60M's, because the headlight is in the nose. On the SP G.E's though, you have high ditchlights, nose headlight, and a relatively featureless logo on the smooth nose. I have found that on these units, and Grand Trunk units, which have no logo at all, my picture sharpness suffers the most. You have to focus on something other than the nose (which actually because of compositional reasons is recommended anyway). I have my best luck with using the edge of the nose that turns back as the side of the carbody. A nice defined line. Obviously with wider focal lengths this stuff is much less an issue than with the big telephotos. For those of you that are still not following what I am saying here is this, the less the contrast on the object you are focusing, the harder for the camera to focus. It is kind of ironic, but what the camera finds hard to focus, I also have a hard time manually focusing. Another easy example, try autofocusing on a smooth white wall (also try manually focusing on that wall). The lens hunts all over the place. Find a shadow line on the wall, and zappo, the camera responds nearly instantly. Now, here is one additional method of tracking you pictures, one that Charlie Dischinger swears by. Set the custom function (#11 I believe), so that your rear Quick Control Dial has control over the autofocus spots. Now you have real time control over what sensor is actually working. Initially, you can set it so that all five are operational as normal, but as soon as you move the dial, only one is available at a time, but with you selecting the spot in real time, you can avoid the camera trying to use an undesirable spot. One last note, that may be obvious, maybe not. When you are allowing the camera to select focus spots for you, typically the camera finds the nearest object, usually because of the proximity to the lens, the contrast is perceived to be higher, and the camera will choose the easiest object to focus on. Even if you have something that is far away that you know has much greater contrast than a nearer object, due to distance and visual conditions (haze, heat distorion), the camera, (and your eye as well, usually) will percieve the nearer object with greater contrast. This phenomena can be used to your advantage, as well as mess things up. I hope this helps out a little more, and may clear up a few loose ends. For what its worth, for the most part, the camera reponds remarkably well, most of the time. Once again it is a matter of learning the system, and what it can and can't do for you. Have fun and GTS, Rick Newton P.S. Although ditch lights are good for the railroads, as far as the autofocus (and autoexposure) photographer, its the devils doing. --> SPORRS: Serious Photographers of Railroad Related Subjects
