[Iroc]

I'm looking to get a little more reach out of my K-r kit lenses (18-55 & 55-300) by using a 2x tele-converter but am unsure which one to get (mounting style, brand, etc.). I'm sure you get better image quality with one of those super-telephoto lenses buy my budget (ie. wife) won't allow that kind of investment. Thanks!

[SOldBear]

For those lenses, don't bother with a TC, particularly a 2X TC.

You'll lose autofocus, and the IQ will suffer significantly.

[manishved]

I would use a Tamron 1.4x or a Kenko 1.5x with the 55-300. Of course, you will lose a stop - so its only useful when shooting in bright light or daylight.

[Pentaxor]

the Tamron 1.4x is really good.

[newarts]

I critically tested a Kenko 1.5x with the DA 55-300mm at 300mm and found it was no better than enlarging the image taken without it.

[maltfalc]

I critically tested a Kenko 1.5x with the DA 55-300mm at 300mm and found it was no better than enlarging the image taken without it.

it's hard to accurately judge the difference when the teleconverter shot is only at 63%, rather than having it at 100% and the other at 150%, but you can see one advantage you get with the teleconverter versus cropping, finer background noise.

[newarts]

it's hard to accurately judge the difference when the teleconverter shot is only at 63%, rather than having it at 100% and the other at 150%, but you can see one advantage you get with the teleconverter versus cropping, finer background noise.

Yes that's true. I hadn't taken the noise aspect into account; it is certainly in keeping with the pixel size change. Here's the same thing at TC=100% I forget what the ISO was (but it was probably 200) & the camera was a K100D on a tripod, etc..


my interpretation of these results was that there's not much to be gained by using this TC with this lens. But I see your point about the noise.

I do think the fair comparison is with the same final image size... that's why one uses a teleconverter - to get a bigger image.

[maltfalc]

in terms of noise alone, printed or displayed at or below the max resolution of the cropped equivalent, a 1.5x teleconverter should give roughly the same decrease in noise as using ff vs aps-c and a 2x teleconverter should give you 1/4 as much noise as a cropped image. i don't know how much this will help iroc or others, but i've taken photos at 600mm with my k110d, a beat up fa 100-300 and an old vivitar mc tele converter 2x-22 that were just as sharp at 100% as photos without the teleconverter.

[Marc Sabatella]

you can see one advantage you get with the teleconverter versus cropping, finer background noise.

Which is pretty much exactly nullified by the one stop loss in light from using the TC (two stops with a 2X TC).

[maltfalc]

Which is pretty much exactly nullified by the one stop loss in light from using the TC (two stops with a 2X TC).

that would only be the case if your shutter speed was so low to begin with that you had to up your iso to prevent motion blur. most of the time a slower shutter speed or using a larger aperture or cranking up the output on whatever lighting you're using or some combination of all three shouldn't be a problem.

[Marc Sabatella]

that would only be the case if your shutter speed was so low to begin with that you had to up your iso to prevent motion blur.

OK, but if you're not already at that edge, then noise is probably not a concern.

[maltfalc]

even at a lower iso, less noise is a bonus. especially if you're trying to bring out details in the shadows or something.

[akanarya]

whic TC do you suggest for 50-135 ?

if x2 is good, then 270mm would be nice FL in case of IQ (wrt tamron 70-300 IQ )