teleconverter for sigma15mm

Hello everybody, I would like to use a teleconverter (1.4 -1.7) with my sigma 15mm on a nikon d610.

Anybody can suggest which one would work?

thanks for your help.

ciao, Flavio

A similar question was raised last year (http://wetpixel.com/forums/index.php?showtopic=56653&hl=teleconverter) but did not get answers. I hope you fare better as my reply won't count as an answer. I just checked out the tread to find out why anyone would want to do this in the first place. It is much easier to make a 24mm lens than a 15mm lens, so why would you add the extra size, weight, glass, and expense of a TC, which also reduces light captured by the sensor, to fake a 24mm and not use the real thing? I also seem to recall that canon teleconverters came with the message that they were designed for use with long focal length lenses and not recommended for wide angle lenses, although that may not be a real concern.

Bart

Thanks for your reply.

Fisheye leneses can be used with a teleconverter to take some close focus wide angle, taking advantage of the close focus capability of the sigma 15 in this case.

ciao, F.

Hi Flavio,

I use a Kenko 1.4 X TC with my Sigma 15mm on a D810. Mechanically, it works fine, but I don't think it gives great mage quality. I actually use it primarily to reduce the fisheye distortion, to give a more pleasing image with big animals. The Sigma is so close focusing, that you can shoot close focus without it!

Hope that helps.

Adam

Adam, many thanks for your advise.

In fact as far as I understand using the TC will reduce the field of view and increase the working distance at same magnification, perhaps I got it wrong.

I will try to borrow/rent one to see the effect.

Ciao, F.

Adam, do you mean this: http://www.kenkoglobal.com/photo/lens_accessories/teleplus/teleplus_pro_300_af_14x_dgx.html

or this:

http://www.kenkoglobal.com/photo/lens_accessories/teleplus/teleplus_mc4_af_14x_dgx.html

thanks again for your advise.

Ciao, F.

I have used the Kenko 1.4 DGX TC with my Sigma 15mm Fisheye behind a Zen 170mm dome with 20mm extension ring (Nauticam housing) and a D800. I didn't notice any image degradation, but at the same time 15mm vs 21mm with that lens was not a big difference.

I have not shot reef scenes with the above so not sure how it'd handle all that detail. I now use a D810, but not a big difference to the D800 as far as IQ, IMO.

I think it shoots big stuff pretty well with the 1.4 DGX.

thanks Camel. great picture!

The one I have is the: TELEPLUS PRO 300 AF 1.4X DGX

The issue with IQ is definitely not one you will see on an internet post!

Image below is at 1/160 which for a slow moving tiger should be fine:

Here is a crop of the image:

You can see that it is a little soft.

Without the TC, the Sigma is tack sharp....

For close focus wide angle (CFWA) a small dome with the Sigma 15mm should focus close enough. For wide angle macro, a TC will be necessary.

You are right that the TC will reduce the FOV, while increasing the optical magnification of the lens. This means that if the subject is very close to the dome it will appear bigger! The reduction in FOV removes some of the "fisheye effect", which is most noticeable close to the edges of the frame.

For close subjects, the biggest issue is trying to light it. Bigger domes make this almost impossible!

Adam

Thanks again Adam for your comments, very clear.

Beautiful the eye contact in your pic.

Were al tiger sharks those on the background?

Ciao F.