Teleconverter issue

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clarkeg

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Clarke
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Hi guys,

I have a Nikon D80 and I was trying to take a few photos of the moon tonight, I have it hooked up to my Nikon 75-300 f/4.5-5.6 AF lens and last week I took some shots of the moon that came out nice and sharp (without the teleconverter). Since then I bought a Kenko Pro 300mm f/1.4 will AF and I was out tonight taking some photos of the moon (same 300mm lens). When I got back home and looked at them on the laptop they are terrible. Really out of focus, I done exactly the same thing as I done last week with the exception that the teleconverter wasn't on and they came out quite well, nice and sharp but I still wanted a bit more reach which is why I bought the teleconverter.

Would this type of teleconverter loose a considerable amount of sharpness with the likes a moon shot? I was on manual focus both times.

Thanks
Clarke
 
I am not an expert on the use of TCs, but I do use them. The first point is that they are normally recommended for lenses slower than f4. At 300mm your lens is an 5.6, the loss of one stop of light caused by the TC would have caused a lower shutter speed so maybe your image quality is down to a small amount of lens shake or blur caused by a slow shutter speed. It would help if you posted a couple of examples.

BTW - you have a Kenko 300 1.4 times TC which is not quite the same as a 300mm f1.4 lens :eek: (that would be a very impressive piece of glass).
 
first of all i recommend if you're going to use a TC on the lens that you mount the camera to a tripod and use manual focus, up the shutter speed and open up the aperture to maintain sharpness of the moon :)
 
Think you need to check up on the lens + converter compatibility.
Very important that you do not link up a teleconverter to an incompatible lens because in some cases damage may result from the lens rear element contacting the converter during focussing.
 
Without seeing a picture, it could be mis-focsued, or camera shake, or both.

Your telecon is a Kenko Pro 300, 1.4x magnification - no mm involved, it's afocal, and no f/1.4. Fitting the Kenko converts your lens into a 105-420mm f/6.3-8. Not sure about how Nikons work with telecons but it's certainly not recommended to use autofocus at f/numbers higher than f/5.6. It might autofocus, not very well, or it might not at all. Use manual focus, as you say you did.

The rule of thumb with long lenses is to use a shutter speed higher than the effective focal length, which is 1/630sec in your case (420 x 1.5 crop factor). So I would set the camera on manual, 1/1000sec shutter speed at f/8 (your new lowest f/number at max zoom) and adjust the ISO until you get correct exposure with a few test pics.

If you have VR (does this lens have VR?) then you could reduce that maybe to 1/250sec which would make life very much easier on the ISO.

Focus very carefully.
 
Thanks guys for all the advice. The lens does not have VR but as some of you have suggested it may be down to my f number and perhaps some movement when I took the photos. I deleted them once I seen them on the laptop so I can't even post them up. I was trying some fairly distant shots today in good light and they came out 100% sharp so I think it may be down to a bit of movement when I took the shots. Looking back I didn't do self timer or remote so that's most likely what has caused the bad lack of focus.

When the moon is out again I'll have another go with all the advice you have given me.

Once again thanks
Clarke
 
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