teleconveter on a macro lens

Can Anybody "in the know" explain the effect a 2x teleconverter would have on a 90mm Macro lens? I have a Tamron 90mm 2.8- will the TC offer this as a good telephoto option at 180mm? Will save space in the bag. I am mainly worried about the AF.

It should work fine I think. I have used a kenko 2X TC with my 100mm macro before with no problems. The 2x TC will cost two stops of light, but that still leaves you at f5.6 which ought to be fine for autofocus. It will probably cost a little image quality as well, but it ought to still give good results. Best bet would be to see if you can try one out with the lens before buying perhaps.

Regards

I have used my 1.5 teleconverter with my tamron 90mm works well.

When used for macro, you will double the minimum working distance (the 1:2 will now give 1:1) and the maximum magnification ratio (the 1:1 setting will become 2:1). It is not 'all gain', however, as you will loose 2-stops, which may indeed affect AF under certain circumstances, and degrade the lens IQ. Whether the perceived 'gains' are worth the 'pain' will depend on the quality of the TC used.

When used in telephoto mode the combinations main potential shortcomings are the loss of 2-stops and the effect on AF.

IMHO, unless you already possess a quality 2X TC (which do not come cheap, even used), the best and most cost effective option would be to purchase a 50 - 200mm DA. These can often be had new for between £50 - £70.00 as dealers dispose of lenses split from bundles and for even less used. Moreover, this is a relatively compact lens and space/weight saving of using a T/C will be so small as to be barely noticeable. Sigma and Tamron lenses covering similar or greater range than the DA are widely available used.

Retiring to the underground bunker now in anticipation of the incoming barrage from the truly 'in the know' brigade

Jon

I've used the Tamron 1.4x and Teleplus 1.5x SHQ converters with the Tamron 90mm Di Macro and they work well. If I get chance Sunday I'll try the Teleplus 2x MC7 and post a couple of results. The Tamron 70-300 LD Di works well in Macro mode 0.95m @ 1:2 if you're after an affordable longer lens.

John

I`ve used the Teleplus MC7 2x on the Pentax A 70-210 Macro, @ 70, which is the macro setting and have obtained very good photos, at about 2.5ft it won`t fill the frame with a Dragonfly, and are very sharp as well.this lens combo is all manual, but you can use the green button,and manual focus which is OK for slow moving shots.

I, too, have been using a kenko 2x converter (MC7), but with my 100 DFA macro.
Although I haven't done a like for like comparison, with & without the converter, I don't see much (any?) loss of IQ.
I usually use the on-board flash on my K7, with a (plastic milk carton) diffuser, so loss of 2 stops isn't a problem & I always focus manually in macro so autofocus difficulties aren't relevant.


[IMG]http://i1021.photobucket.com/albums/af340/rogerhlane/OldBlueEyes003adjcrop.jpg[/IMG]

It's a combination I would certainly recommend.

Coker.

Thanks for the upload Coker- What a beast! I am on the lookout for a TC.

I use the Pentax 1.7x on my 100mm D-FA.

I sold my Sigma 180mm 3.5 macro soon after I started .. couldn't see much point keeping it.



Shield bug by Mike.Pursey, on Flickr



Dragonfly by Mike.Pursey, on Flickr



Spider by Mike.Pursey, on Flickr

The TC used here is only a budget 3x macro focusing model, but it still proves useful occasionally. This uncropped shot is of a a tiny spiderling only about 2-3 mm long, which my 100mm macro struggled with on it's own.




I these situations I usually add a reversed 50mm as a close up lens, but for a change I tried out the macro TC (Having just tried it out with the 600mm reflex)

The additional focusing power of this TC gets in significantly closer. (Its designed to be used to get to 1:1 with a 50mm prime.)

Almost right.
The minium focus distance will stay the same but your focal length is doubled, that's why the magnification is also doubled.

Just try it out, the distances on the focus ring still are correct.

"you will double the minimum working distance (the 1:2 will now give 1:1)"

Surely you meant to say HALVE not DOUBLE?

No, Stefan is right. A 2x converter will double the magnification from 1:2 to 1:1, for example. The focus distance remains the same, hence the extra magnification. You also lose two stops, so a 50mm f2 lens would become a 100mm f4.