Using Tamron P/KA mount on K100D

Hi,

New to the forums and not sure if this problem has come up in the past or not. Soory if it has already been discussed.

I have a Tamron Adaptall-2 60-300 mm zoom with a P/KA mount. Bought years ago in the days of film and still a great lens. I am now using it with a K100D, but I am not entirely happy with the results.

I use the lens most often for airshows, since I have a new Pentax 50-200 for routine zoom use. With the Tamron, I am having problems with getting consistent exposure. I always need to underexpose by 0.5 or 1.0 stops. When it works, it works great. But on a single pass of an aircraft, I might get a couple of shots that are well exposed, mixed with shots that are overexposed. It seems like the camera is searching for the right exposure. I am usually shooting in Tv mode at 1/250 to keep a reasonable amount of prop blur on prop driven aircraft, with higher speed for jets.

It is frustrating to come home at the end of the day and have to delete so many othewise great shots. Any advice? Is there something I am doing wrong? Could it be related to the contact problems with the P/KA adaptor that I have read about on other sites?

Thanks

You are setting the camera a very hard task.

In the "foreground" is the plane, which may or may not be silvery or dark, and in the background is the sky which will be very much brighter than the underside of the plane.

Furthermore, depending on the plane's position (level, banking, whatever), there may be more or less sun on the underside.

If you are using average metering, the camera has to work out how much it must discount the brightness of the sky in order to get the right exposure for the plane. No easy task.

If you are use spot metering, and the underside of the plane happens to be not too dark and not too bright you might have better results.

There are lots of experienced plane snappers on here who can tell you what they do, but I would be tempted to use manual after first trying a few shots to see what works. Of course, that won't work very well if the light keeps changing.

G

With the lens on the camera go to AV mode and gently wiggle the lens left and right while watching the aperture on the lcd. If it changes then you have a dodgy contact. I have had it on one of mine but it tends to drastically overexpose, not by a stop.

I have found that the Adaptall lenses do tend to overexpose the further you are from the subject and are prone to giving a terrible haze on pictures taken with a zooms maximum range. .. saying that I wouldn't part with mine.

George, you are right, shooting like that can be tricky. The problem is that one shot is fine, and the next, taken a second later on the same pass, is drastically overexposed as Mike puts it, so that even a little tinkering in Photoshop can't save it. And that with the camera set to underexpose.

If the lens/camera combination is consistent in its exposure then that is fine, and I can adjust accordingly if it is a little off. But to have good exposure in one shot, and then have drastic overexposure a second later, and then go back to good exposure a couple of seconds later ... well I can't adjust for that and I can't explain it. Hopefully someone else can.

I'll see if I can post a couple of examples, with exif information from both. I just need to retrieve the overexposed shots from the recyle bin

Thanks

If you are getting the same inconsistency with "normal" shots (not planes; people in the street, landscapes, etc.) then I would say you have some sort of equipment problem. But if it's just with the planes, then I think it is because from shot to shot you are getting different amounts of plane and sky in the picture, and the meter simply can't make its mind up.

G

Just to double check that your lens actually has an "A" on the aperture ring? If not, then your camera will be working in Av mode regardless of what other auto mode you set, and at open aperture.

This would mean that as you pan across the sky at some points the fastest shutter speed available may not be fast enough to prevent over-exposure.

Just a thought.