Weird 1.4x convertor problem...

ukaskew

ukaskew

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Chris
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I have a Nikon D50, Nikon 80-200 2.8 AF-S and the latest Nikon 1.4X convertor (TC14E-II or something like that), whilst I'm constantly amazed by my 80-200, it seems a bit hit and miss when the convertor is attached.

If I'm using slow shutter speeds such as 1/200 and slower (which, thankfully, is most of the time) it's fine, but when I go faster it loses the plot more often than not.

First pic is an example of when it decides to work ok...


198960776-L.jpg



Second example is at a faster shutter speed when it goes a bit blurry...


241971185-L.jpg


Zoomed in view of the problem...

241973010-L.jpg



It just seems to develop that 'haze' 90% of the time when using it at more conventional shutter speeds.


Any ideas/thoughts?
 
CT said:
Which AF spot was enabled?
Click to expand...

Can't remember to be honest, probably just the centre one. Although I have shots taken from the exact same spot seconds earlier that did come out fine, it's just that 90% of them get this weird haze effect. It's over the entire frame though, not just the car.

Just found an example of one that was fine, same spot, same settings...

198987501-L.jpg
 
Going on the basis that you've got enough data to rule out all the simple focus problems, it's a pretty weird one isn't it.

There is no way I can see that a TC can have an effect on a lens that's govened by shutter speed. It just doesn't fit into any part of my understanding of the physics of light.

However unlikely it seems, I can only think of some software/electronics issue that is causing a focus malfunction under a certain mix of conditions. It doesn't make much sense but it's the only theory I've got so far that fits the facts. :shrug:
 
dazzajl said:
Going on the basis that you've got enough data to rule out all the simple focus problems, it's a pretty weird one isn't it.

There is no way I can see that a TC can have an effect on a lens that's govened by shutter speed. It just doesn't fit into any part of my understanding of the physics of light.
Click to expand...

It is indeed a weird one, I've probably taken 10,000 shots at speeds slower than 1/200, and it's not happened a single time. However get to faster speeds and it keeps happening a good 80-90% of the time. It's also worth pointing out that I have absolutely no problems with the 80-200 on its own regardless of shutter speed.

I know when it's going to happen so I avoid it whenever possible, but occasionally I forget about it, hence these examples.

Here is another example...

http://chrisharrison.smugmug.com/photos/241965269-XL.jpg
 
Well fitting a converter does slow down the AF a bit but there's no reason why using a faster shutter speed should result in softer shots, quite the reverse in fact.

If you open your pic of the black car in your image editor and work out the exact centre (use the grid lines) it looks like that AF point would have been just to the left of the offside rear light right on the black bodywork with no detail to focus one which could well be your problem. Black cars have to be bad news anyway, look how all the tiny body detail, scoops and stuff is lost in comparison to lighter cars, and that's all detail your AF system can lock onto.

I don't do any motorsport togging but I'd have thought you'd be better using multi AF points - see what the motorsport guys think.
 
It's not like any 'out of focus' shot I've ever seen, which is why I assumed it may be an internal issue. I've taken more than my fair share of out of focus shots and they've never looked like this. It just looks like a film of haze covering the entire image.
 
Hmmm, what shutter speed was that evo shot at.

It doesn't look like a fast shutter speed from the wheel blur does it. I'm wondering if, whether for some odd reason the camera is not actually giving you high shutter speeds with the TC on when you're thinking it is.

Still baffled, just trying to throw suggestions at you.
 
Evo was 1/320, I've got plenty from the same spot at 1/250 which are perfect. Interesting that it's a black car again though, I will have to see in the morning if it's happened on lighter coloured cars.
 
Ok then, that looks about right for 320th at a fast-ish part of the circuit doesn't it.

A combination of a black surface, the TC and continuous AF just missing the mark a tad I could buy into..... just.

Still doesn't really explain why it only happens over 200th though. :thinking:
 
If you check out that Evo shot the centre AF point is again on the bonnet with nothing to maintain focus on.

If you're using one AF point and servo AF, the camera needs to continually have enough contrast in that one AF spot to maintain servo focus. Obviously as soon as that AF spot loses enough detail to focus, as it has here, the lens starts to hunt, which is just as you've taken the shot.
 
^^^ Starting to make sense now, to be on the safe side I will pop out and take some test shots tomorrow to see how it goes. I've literally never used it when not pointing at fast moving cars, so I will point it at some brick walls or something and see what happens.
 
When I'm shooting birds in flight I enable all the AF points on the 20D and it works pretty well.

The 1D MK2 has a nice option where you can reduce the number of AF points and just use a few in the centre if you think the system may lock onto the bg, but there's no way I could keep them in focus with one AF point. OK.. your cars are bigger but they're going waaaay faster! :D
 
ukaskew said:
^^^ Starting to make sense now, to be on the safe side I will pop out and take some test shots tomorrow to see how it goes. I've literally never used it when not pointing at fast moving cars, so I will point it at some brick walls or something and see what happens.
Click to expand...

I was going to suggest testing it on a static subject with a tripod, to see if it is a focusing problem etc.
 
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