An experiment

Not having £600 to purchase the Sigma lens I wanted and being very dissatisfied with my 2x converter I spotted this for $99 and decided to give it a go:



It is a Bower 2x converter that goes on the front of the lens! (62mm thread)

Here are my test shots (only to illustrate speed and magnification, all hend held and taken through a window):



Sigma 18-200 @200 f9.0 ISO 100 1/320



+Tamron 2x @400 f9.0 ISO400 1/200
(Focus has some trouble locking on, slower and more noisy)



+Bower @400 f9.0 ISO100 1/250
(vinyeting visable but focus unaffected and much better light performance)



Sigma UCII 70-210 55mm filter thread.
+bower @420 f9.0 ISO100 1/200
(No step up ring so held infront of lens)

Colclusion so far is that the vinyetting makes the Bower unusable on the Digital only lens but if I have gone for a bigger thread size on the Bower, that might have been less of an issue. However, on the 70-210 35mm image circle lens (I can't do a full test till I have the step up ring) I seem to have a very usable 140 to 420 zoom that performs much better than the Tamron 2x converter. Weight isn't bad either. and this cost me only about £64!

Once I have the step up ring I will post some more test shots - I may even use my tripod this time!

The rear teleconverter shot is much better than the ones made with the front teleconverter...

Have to agree with Tyr, the image quality from the Tamron is way ahead of the Bower. The Bower gives a smeared effect, looks more like a lensbaby.

Dan

That is true, however with the Bower, the set up is much harder to hand hold (on count that it is heavier than the Tamron), that is why I need to do more tests - the shutterspeed needed to be closer to 1/400 to ensure camera shake was catered for. I plan to shoot with the 70-210 at equivalent of about 200 for all the test shots to see the difference - this time I will use the tripod.

I have ordered the step up ring and will hopefully get it within a week and will post the results then.

I think the colours from the Bower are better. I also think your choice of shutter speeds for these shots is a tad optimistic for hand held operation. I know SR is good, but . . . . ?

Try again with a tripod (SR off) and no window and use a shutter speed of the reciprocal of the effective focal length. EG: For an effective focal length of 900mm, use 1/1000th of a second as a minimum. Vignetting can be fixed in PP.

Roll on the next bright sunny day!

Vignetting can be resolved, however, the objective is to get the best in camera - a true alternative to a standard 2x converter.

I think I had SR off due to the lack of communication of the true focal length which is required for the best SR results.

I would try to set up a good test situation first. Taking pictures through glass will nearly always affect lens performance, and the longer the focal length the worst the affect will be. Get outside and try again using a tripod. Try several shots with slightly varied focus 'cos I find I can't always trust my eyes 100% on a matt focusing screen. Try subjects at different distances too. I don't think you will get brilliant results from a front converter though.

I too am yet to be convinced, however the obgective of the first test was to look at auto focus capability and effective lens speed - both proved better with the front converter! Now it is time for the image quality tests. I am planning to shoot as close to identical mm with and without the converter. All tests will be done using AF to see if the AF function is affected at all.