Hi! I was thinking about a way to save money, and get a faster lens. I am wondering, will a tamron 1.4x extender work with a Canon 100mm f/2 lens? Wouldn't this mean that I could then have a 140mm f/2.8 lens, which could replace a need for the 135mm?
I believe it will work but you will have some loss of IQ with any tele extender as you are adding another layer of glass. Your AF will likely hunt some more also in my experience.
brockwhittaker wrote:
Hi! I was thinking about a way to save money, and get a faster lens. I am wondering, will a tamron 1.4x extender work with a Canon 100mm f/2 lens? Wouldn't this mean that I could then have a 140mm f/2.8 lens, which could replace a need for the 135mm?
Thanks,
Brock
will it make a good 140/2.8 ? probably . will it make a replacement for a 135L ? No way
having used TC's on various lenses for a test I will concur that there is no such thing as a free lunch.
a 1.4x will not normally do too much to IQ as in general the results are pretty good, but you do usually get a more 'nervous' bokeh . also sometimes you may find you have to stop down a tiny bit. so you can think of it more as 140/4
If you follow this path, I suggest you get a Kenko Teleplus Pro 300 DG 1.4x Teleconverter instead of the Tamron. I suppose the newer Kenko "DGX" model is just as good as the "DG", but I haven't tried one. The Kenko has virtually the same performance as the Canon EF 1.4x Extender (which I had) and Mk II (same optics as Mk I). The new Canon Mk III is better than all of the others, but not by a huge margin.
The Tamron SP AF 1.4x Teleconverter isn't bad, but the Kenko DG is noticeably better in the corners. The "non-SP" Tamron TC's aren't very good.
I have the Kenko Pro 300 DG version and jcolwell is correct. However there seems to be a problem when putting this TC on the 70-300L lens. It will hunt for quite a long time. So do I need to buy the newer "DGX" version.
The 70-300 is probably too slow of a lens to autofocus with a teleconverter and the body you are using. Probably has nothing to do with the converter. The camera's auto focus system needs a certain amount of light to work properly. Usually f5.6 or f8 on 1 series bodies.
ggibbs1971 wrote:
I have the Kenko Pro 300 DG version and jcolwell is correct. However there seems to be a problem when putting this TC on the 70-300L lens. It will hunt for quite a long time. So do I need to buy the newer "DGX" version.
A different TC will have little on no difference. As has been said above a 5.6 lens with a 1.4 TC added is too slow for your body to AF .
However I have tried many different combos on a few bodies (40D included) and here's what I've found.
The 40D will AF on all points at f8 but the outere points are better. At f11 (5.6+2x) the centre point is inactive but the outer points still work.
You will need good light and a higher contrast subject to get a consistent lock. And don't bother trying stuff that moves faster than a snail
The 7D however won't AF on the centre point with any TC added to a 5.6 lens . Again the outer points are a lot less fussy
Previous bodies that I have tried have been a lot less discriminating . The 30D & 450D I tried would both attempt to lock at f11 on the middle point.
Of course all of the above has been done with non reporting combos. Either the TC has been taped or the lens has not had the 3 extra TC contacts.
Like this I have noticed a few metering errors. It can be quite alot . Upto 2 stops over exposed with the 2x TC on my 40D . The 1.4 was not so bad but I would see around 2/3rds stop over expose (sometimes a full stop)
I found it much better to meter a scene without the TC and then shoot manual . Of course you have to remember that the body is reporting the lens at 5.6 but your really at f8 or f11 (depending on the TC)
