Teleconverter and moon shot

posted March 16th, 2017
Hi,
Some technical advice please! I have a 75-300 f/1.4-5.6 lens. I bought a (Futin?) 2x teleconverter in a thrift shop. Aimed this at a nearby tree, the edges were very blurry, centre ok. This morning I aimed it at the moon, thinking with a clear sky I don't mind that part blurry, but no matter what I did could not get the moon in focus, just one large blurry ball. Shot talking a minute after with just the 75-300 turned out a sharp moon. Was I aiming for somethiing impossible or doing something wrong?
Thanks!
posted March 16th, 2017
@saskiah i cant help you too much but i want to see the photo as it sounds quite interesting AND i just realised we have the same name!!! i don't ever remember coming across someone else with my name :D
posted March 16th, 2017
2x converters do have a reputation for being rather soft, even the expensive high end ones. So it might never be "perfect" but you can do a few things to help. I'm not expert at anything, and you're probably doing most if not all of this stuff already but i'll list it anyway!

If you're using autofocus, converters can cause this functionality to stop working properly due to reduced light, so manual is recommended if not mandatory (if you're already doing this then ignore that bit). Increasing the f number can help a bit (usually f8 or more), along with usual things such as tripods and remotes (or just use a delay) to help remove any shake blur.

One final thing is if there's one situation to ever use RAW in it's moon shots. Them being greyscale means that in a jpeg you'll not have much space to edit in, so using RAW will give you a bit more wiggle room.
posted March 16th, 2017
I am afraid there is little you can do with a cheap teleconverter. As @miseria said, Auto Focus will almost certainly not work. A x2 teleconverter while doubling the focal length will double the effective f/stop by two. (f/stop number = Focal Length / Diameter of Iris). This is Four Stop loss of exposure, so you will need a shutter speed four times as long, all things being equal. You certainly will not be able to hold the camera steady enough even if any VR on the lens will still work with the teleconverter.

You can try mounting the camera on a sturdy tripod (almost essential for any good moon shot whatever the lens), manual metering and manual focus (using live view), but don't expect too much. Sorry. As you saw, you will probably get better shots with the lens by itself and then blow up the image in an editor.
posted March 16th, 2017
To go along with what @miseria and @frankhymus have mentioned, I purchased a 2X Vivatar expecting wonderful shots, and have yet to find any sequence to get a good, crisp, clear shot. As mentioned, on autofocus, it will hardly ever lock in. If I use single point focus, it does lock in, but the shots still come out really soft and blurred around the edges. I do use a tripod and use the electronic shutter control, so I should be taking all shake out of the picture. I've also tried the manual focus, with little success also. I have read that the 1.4 teleconverter works a whole lot better, but have been afraid to try one of those, expecting the same thing. I have seen where Photocrazy uses a 2X on a lot of his pictures, and his comes out totally awesome. But from all of his shots, I suspect that he has invested in the top of the line glass and teleconverters. I still try every now and then, but have pretty much just stuck with the lens by itself. Good luck.
posted March 16th, 2017
Thanks all! I expected the blur around the edges, and I used a tripod and (tried) manual focus. (Wish I could post the blurry moon here!) I shot in RAW, and it gets a little (but not great) better if I lower the exposure...
I guess investing in quality equipment is key!
posted March 16th, 2017
@sasslater Photo is grey/black wth a blurry yellow circle! You must be of Dutch heritage then!
posted March 16th, 2017
@saskiah Many of the cheaper teleconverters won't allow infinity focus - your problem could be as simple as that.
posted March 17th, 2017
@vignouse And that must be it! Thanks!
posted July 9th, 2017
Sounds like the limitation of the teleconverter is most probably it.

If you can you get the shot in focus looking through the viewfinder but the shot is coming out as a blob it might be that some exposure compensation is required and the moon is getting burnt out as it is over exposed but from your description it sounds like you just cant get focus in the first place. It was the mention of it being slightly better in raw that made me think it might be this. Also bear in mind that the moon and earth are moving so if your exposure is too long you may get blur from that too!



posted July 10th, 2017
@lizhammond Cheap teleconverter, I was able to get a decent shot with a zoom lens.
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