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Teleconverter with fast 50s

BarneyL
Posted 18/05/2017 - 13:47 Link
Hello everyone,

I've recently come up with an idea to use a 1.4x TC with a fast normal prime to achieve (kinda) fast, portrait 70-80 ish mm lens. I know that this combination probably won't yield an equivalent of 70mm ltd (to put it lightly), but I wonder what the results could be. I have a few manual 50-55mm 1.4 lenses - although most of them in M42 screwmount - and thinking about testing this idea in practice. What do you think? Did you try it yourself? Also, does the HD DA 1.4x TC work with screwmount lenses (using M42-K adapter, of course)?

Cheers
K-3 II, DA 16-85, DA 55-300 PLM, FA 43, D-FA 100mm WR, few S-M-C Takumars
johnriley
Posted 18/05/2017 - 15:22 Link
TCs tend to be disappointing, but 1.4x stands the best chance of being OK. A 50/55mm f/1.8 or f/2 will be more likely to be optimal than an f/1.4 or faster.
Best regards, John
smc
Posted 23/05/2017 - 18:41 Link
I would go for the 1.4 but stop down to f1.8 or f2.0.

The results might be ok for portraits as biting sharpness is not necessarily required.
JAK
Posted 23/05/2017 - 19:22 Link
smc wrote:
The results might be ok for portraits as biting sharpness is not necessarily required.

Don't tell sebas77 that!
John K
smc
Posted 23/05/2017 - 19:54 Link


JAK wrote:
smc wrote:
The results might be ok for portraits as biting sharpness is not necessarily required.

Don't tell sebas77 that!

davidwozhere
Posted 24/05/2017 - 00:00 Link
Both the rear converter-A 2xS and the K T6 2X work very well with M42 lenses but the slight quality loss (and fall in available light) is inescapeable - it comes with the territory whatever sort of converter you use. The light must travel further so it's intensity falls and it spreads out twice as much as when the converter was not there. As well as magnifying the image, it will magnify all the faults of the lens on the front, so you want at least a Takumar f1.4, or a Helios 44M-4 or 44M-7 or similar.
Both the *istDS and the K5 are incurably addicted to old glass

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johnha
Posted 25/05/2017 - 00:36 Link
I've used TC's (2x and occasionally 3x) with a variety of formats (APS-C, 135, 645 & P6x7), with a good 'standard' lens or longer they usually work reasonably well (comparing them to the equivalent 'longer' lens). The only combination I've had problems with was a Vivitar 2x M42 TC with a SMC-Tak 50/1.4 on a Spotmatic (all very used) - there was a weird artefact dead centre of the image I couldn't account for. The same TC on a SMC-Tak 135mm worked fine.

For portraits (where sharpness isn 't necessarily the most important aspect) the results might be exactly what you're looking for.

That said, if you haven't already got a TC (or unless you can find one cheaply), I'd consider another lens - my suggestion would be an SMC-Tak 105/2.8 or similar - not ridiculously expensive like an 85/1.8 or 85/2 and easier to find than K mount 85 or 105 lenses (excepting £££ for the 77 Ltd). Another option may be the K 135/2.5 - although a bit long for portraits it ultimately depends how much space you have.

You don't mention which format - if APS-C a 50/1.4 (or f/1.7 or perhaps f/2) is more than adequate given the scaling factor.

Some TC's seem expensive and only viable if you're going to use them heavily, the HD 1.4x springs to mind as does the vintage Pentax-F 1.4x 'AF adapter' - the later would provide limited AF capability with M42 lenses!

John.
LennyBloke
Posted 25/05/2017 - 08:22 Link
My experience has been that using a tele-converter with almost any fast lens will give poor results wide open with the benefit only really coming when stopping down a stop or so (thus losing the advantage of the fast lens).

High end telephotos seem to respond better to tele-converters, but it's important to get a good quality one in my view.
LennyBloke

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