Teleconverter - safe to use with Sony 500mm reflex lens?

[TFD]

I have the Sony 2X teleconverter (TC), which I use with my Sony 70-200 G lens. The User Guide for the TC warns not to use it with any lens other than 3 specific lenses, or damage could result.

I want to try a 2X TC on my Sony 500 reflex lens for some moon photography. I assume I shouldn't use the Sony TC on that lens, per the User Guide. Any suggestions - should I try a Sigma, Kenko, or other aftermaket TC on the Sony 500 reflex?

Thanks!

[David Kilpatrick]

Depends on your camera. The Kenko 2X DG7 8-pin TC will definitely work with the 500mm, but it can not autofocus due to f/16 aperture. On an OVF camera is it virtually useless. However, on the A55 with the electronic finder you might as well be using and f2.8 lens, the screen is perfectly bright and you can focus manually with accuracy. What you can not do is hold the camera steady by hand, it's amazing how much shake you get at 1000mm seen on screen!

The Sony or Sigma converters can not be used, the 500mm rear mount baffle won't fit into the mount of the converter, so they are incompatible.

The results look acceptably sharp, that's the best I can say. I would need much better light to check it properly.

David

[TFD]

Thank you, David. I'd be using the A900 on a tripod. I read your note to say that, at f/16, I would not see the moon well enough through my OVF to be able to focus accurately with manual focus - do I have that right? Perhaps a 1.4X TC would be useable? If so, B&H here in NY carries Bower, Kenko, and Vivitar TCs for the Sony mount - any preference on brand? Thanks again for your advice!

[David Kilpatrick]

The A900 is not the best choice for the Moon. With a 1000mm lens, the Moon is I think 8mm diameter imaging. The best camera for the Moon is a 16.2 megapixel APS-C, which would also allow live view focus. With the A900, you only have the resolution of an 11 megapixel APS-C. You could make test shots and examine them for focus, making very small changes. My experience is that tiny changes to the focus are significant with Moon pix.

David

[InTheSky]

I don't know if the 500mm Reflex your got is very good ... but I have found that already with the 12MP of the A700 ... the detail of the lens can provide is already limit... so I see no point of a 2x on it ... where up scaling digitally the picture will probably better.

Regards,

Frank

[Edgars L]

Agree, with TC AF does not working and upscaling gives you the same result. In addition with upscaling you will keep AF. I would suggested to invest in 1.4x TC rather than in 2x TC. With 500mm neither of them will give some benefit, but with other lenses 1.4x is much more worthwhile.