Kenko TCs

[Bally]

Dear all,

Some quick questions re Kenko TCs, the pro 300 range I think

Can you stack kenko TCs, I understand this is not advisable, for a number of reasons.

If so, I assume the light loss is additive so how many of these could you stack say on an f/2.8 before it would not work due to light loss, (forget image quality)

Does anybody have a definitive list of which Canon lenses these thing work with, I understand that they recommend not to be used on a lens below 50mm, because of extreme vignetting, but I want to know if you can put these things on a wide or ultrawide lens and not damage it.

Also understand or believe that they only work on EF, is this because you will damage either both if you connect them to and EF-S or again vignetting or the image will only get to part of the sensor?

All of this is theoretical, and I know a lot of the arguments for and angainst TCs, but I become frustrated trying to find an answer to this, and so thought I would come to the wise people here and see what sort of response I would get.

I have googled the #*^%& out of kenko TCs and all sorts of things and haven't been able to find out.

Cheers

[Darey]

Bally,

Up front I will tell you I have Nikon D90 & D80 bodies and both the 1.4 x and 2 x Pro 300 Teleconverters. So I can only tell you my experiences from the Nikon angle.

It is recommended in all cases that when mounting a TC to first attach the TC to the Lens and then mount the combined TC & Lens on the camera. This apparently minimises the possibility of damaging the electrical contacts and aperture adjusting lever on the camera.

1.4 x TC
Generally the IQ remains almost unaffected, light transmission drops about 1 f stop and the focus speed with AF-S or AF-I lenses remains accurate and fast. When using AF lenses (where the internal camera AF motor drives the lens AF) the speed of focus slows down slightly and is slightly more noisy. With a Tamron 200-500mm zoom I found the IQ remained good to very good but AF slowed down slightly, got a bit noisier but remained very accurate. With a Sigma 100 - 300mm HSM lens the IQ remains excellent but the AF will no longer work. Sigma HSM lenses will only AF with Sigma TCs.

2 x TC
Generally the IQ remains good to very good but is slightly affected , light transmission drops almost 2 f stops and the focus speed with AF-S or AF-I lenses remains accurate and fast. When using AF lenses (where the internal camera AF motor drives the lens AF) the speed of focus slows down slightly and is slightly more noisy. With a Tamron 200-500mm zoom I found the IQ remained good but AF slowed down slightly, got a bit noisier but remained very accurate. With a Sigma 100 - 300mm HSM lens the IQ remains good to very good but the AF will no longer work.

1.4 x plus 2 x TC combined.
I always mounted the 2 x TC to the lens first, mounted the 1.4 x TC to the 2 x TC then mounted the TC Lens combination to the camera. You may notice the mounts feel loose but I haven't experienced that having any affect on how the combination operates.
Generally the IQ remains good but is affected, light transmission drops 3 f stops and the focus speed with AF-S or AF-I lenses remains fairly accurate and fast but you need good to very good light. When using AF lenses (where the internal camera AF motor drives the lens AF) the speed of focus slows down quite noticeably and is noisy. With a Tamron 200-500mm zoom I found the IQ remained good but AF slowed down dramatically, got a lot noisier but remained accurate in good light. In poor light manual focus had to be used. The reach of this combination was unbelievable. With a Sigma 100 - 300mm HSM lens the IQ remains good but the AF will no longer work.

One thing I did notice is that the Depth Of Field appeared to become very narrow. (ie: at f8 on the Sigma the DOF appeared to become equivalent to f 2.8. ( Maybe someone else more knowledgeable can explain why this is so.)

Irrespective of what combination you use I believe you MUST USE A TRIPOD to get the best results and don't expect miracles.

Hope the above helps.

[Old Skool]

I have a Kenko 1.4 Pro 300 teleconvertor. You can only use it on a EF lens, EF-S physically won't mount. Used mine on 50mm 1.8 no problems and on 70-300 OK. You do lose some quality though and I reckon you get more CA with it fitted. Also find that with the 70-300 it will only auto focus with centre point focus, even then hunts a little.

[Bally]

Thanks Darey that answers one of my questions, and all the rest of it is very good information too, thanks for your help.

[Riverlander]

One thing I did notice is that the Depth Of Field appeared to become very narrow. (ie: at f8 on the Sigma the DOF appeared to become equivalent to f 2.8.

As I understand it this is because the change in f stop is caused by loss of light and not because of a physical change in the diaphram opening of the lens. That means if the lens is physically at f/2.8 and you put a 2x TC on it, then you lose 2 stops -- you get f/5.6 -- but the lens is still physically on f/2.8.
I use a 2x TC on my f/2.8 lens quite often, and I shoot at f/11 which means that the lens diaphtam is physically on f/5.6, which is probably its sharpest setting.

I have had both Kenko TCs in the past (Sigma now) and they fitted every Canon lens that I tried them on.

[Bally]

thanks Graham, any chance you could expand on "every canon lens that I have tried" Particularly wide and ultra wide if any?

[Riverlander]

Can't expand really as it was a couple of years ago and I do forget. However I have had a reasonable range of lenses for years, so I had no need to use the TCs on any of the wide ones.
If you gently try to put them onto a lens you will soon realize whether they will fit or not. If they go on nice and easily they will not damage anything once put the TC plus lens onto the camera.

[R1titan]

I have the Kenko Pro 300 1.4x TC and it will not mount on EF-S lenses as already mentioned due to the physical protrusion on the mount.
However, it does mount onto third party lenses that are APS-C designated and retains AF well although a little slower due to the loss of light.
Unless you are using a 1D series body, you will lose AF where the minimum aperture is higher than f5.6.

I did find that if i stacked TCs (i also have a Canon 2x II TC) in the order that Darey stated, with a 3 stop loss of light (f2.8 dulled to f8) the camera does not register that the Kenko is there and reads an aperture of f5.6 which allows it to still focus, albeit slowly

Now u just need to decide whether using TCs or cropping is more appropriate for your use...

[kiwi]

I cant really understand why youd want to put a TC on a wide angle lens ?

[Bally]

Kiwi,

Not sure that I would, although I gues that it would offer some added versatility, The main thing I wanted to know was if it was possible, and if there was a list anywhere of what lenses these had been used with. The Kenko pro range seem to offer the most versatility in what lenses they can be attached to, and reasonable IQ from all reports. THe canon TCs seem to have a limited range of what they can be added to, so I guess what I really want to know is can I carry one of these suckers and use it on any EF lens I have available to me at the time.

for example the 17-40 which is 27ish to 64 FoV on 50D would become 54-128 or 38-90 with a 2 or 1.4 which to me seems very flexible