Kenko DGX 1.4x potential issue

DizMatt

DizMatt

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hi
If anyone can help with this query that would be great.
I've done a search for threads on the TC but there aren't many that are helpful.
Anyway, I use the TC occasionally with a 7D and sigma 70-200 OS f/2.8
results are okay, but I've noticed that when I go over 1/400s that an unusual instability happens to the point where frames per second drop to 1 or less per second and the shutter "jumps" as the picture is taken.
has anyone else heard of such an issue?
thanks
 
I use this converter on my canon 70-200L f4is with a 550d and it works well with it
 
I bought a Kenko DGX 1.4x (Pro 300 - is that the same version as yours?) and it works without issues on both my Canon 100mm F/2.8L IS Macro (which is why I bought the Kenko) and my Canon 70-200mm F/4 IS on both a 70D and 7D Mark II body.

Did you buy it new? Warranty? It does sound like a fault just on yours unfortunately.
 
pingu666 said:
does the lens/body know the tc is there?
that might cause the issue :/
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....Yes. If you look at a TC you will see electronic contacts and those connectors allow body and TC and lens to communicate with each other.

Btw, ALWAYS attach any TC to the lens first and BEFORE mounting both together as one onto the camera body. If you don't do that you risk disturbing the communications.
 
they did passthrough style ones, so there was no chip in the teleconverter that said "hi im a tc 1.4" to the camera, which gives obivous advantages/disadvantages, so the camera doesnt know the teleconverter is there
 
pingu666 said:
they did passthrough style ones, so there was no chip in the teleconverter that said "hi im a tc 1.4" to the camera, which gives obivous advantages/disadvantages, so the camera doesnt know the teleconverter is there
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....I think you are referring to lens extension 'Tubes' and not 'TC' converters (Canon call TCs 'Extenders'). I don't know if some tubes lack lens > < body communications.
 
crofter said:
Some teleconverters (extenders)do not report to the camera, I had a Tamron 1.4x (made by Kenko) that didn't and didn't show up in the Exif info.
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....We learn something new everyday and it's still early in the morning :D.

I personally wouldn't want a teleconverter which didn't report full data to the camera. Do such teleconverters report from body to lens?
 
RedRobin said:
....We learn something new everyday and it's still early in the morning :D.

I personally wouldn't want a teleconverter which didn't report full data to the camera. Do such teleconverters report from body to lens?
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It's just as if the teleconverter is not there, the only advantage I can see is you don't lose autofocus with some lenses as although you lose a stop of light the camera doesn't know this.
 
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crofter said:
It's just as if the teleconverter is not there, the only advantage I can see is you don't lose autofocus with some lenses as although you lose a stop of light the camera doesn't know this.
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....This might be a bit pedantic or academic, but when some DSLR bodies lose a stop of light and the sensor consequently doesn't physically receive enough light, doesn't that either kill autofocus or create AF problems?
 
RedRobin said:
....This might be a bit pedantic or academic, but when some DSLR bodies lose a stop of light and the sensor consequently doesn't physically receive enough light, doesn't that either kill autofocus or create AF problems?
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No idea., some folks tape 3 of the pins on a converter to avoid reporting and to try to retain AF,(never tried this myself) if I remember right these three pins were not on the teleconverter I had.
http://www.michaelfurtman.com/taping_the_pins.htm
 
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Thanks everyone for the comments.
Yes new. Under warranty but ebay i think.
I will see if attaching to the lens first works. Turning camera off etc is only over a certain shutter speed so quote unusual .
Also this does communicate with the camera for football length etc
 
RedRobin said:
....This might be a bit pedantic or academic, but when some DSLR bodies lose a stop of light and the sensor consequently doesn't physically receive enough light, doesn't that either kill autofocus or create AF problems?
Click to expand...
Yes.

Most Canon DSLRs have a firmware limit so they will only try to AF when the maximum aperture of the lens (or lens+TC) is f/5.6 or better. Some of their pro bodies (1D series, 5D Mk III, 7D Mk II) will allow AF when the maximum aperture is f/8 or better.

Canon Extenders always report their presence to the camera (except when you stack them, but let's not go there). So for example if you have an 800mm f/5.6 lens and a 2x Extender, that's 1600mm f/11 and no Canon DSLR will even try to AF. However if you have a non-Canon teleconverter which doesn't report it's presence to the camera - or if you tape over some of the pins on the Canon Extender to achieve the same effect - then the camera thinks it's still got an 800mm f/5.6 lens attached and it will try to AF. It probably won't succeed unless the light is very, very good, and it will be very slow. That's why the firmware limit is there, of course. But if you're lucky it might work.

Learned something new?

edit - Incidentally Nikon DSLRs don't work the same way. They don't have the firmware limiter, so the camera will always try to AF. They won't AF reliably beyond f/5.6 for consumer bodies or f/8 for pro bodies - just the same as Canon in that respect - but they will try.
 
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I stacked a 2x sigma and ahte 1.4x kenko on a sigma 70-200 OS f/2.8 lens. and it auto-focused on the centre.
it wasn't speedy of course on a 7Di. It was an experiment, I didn't even look at image quality in detail.
 
For what it's worth, because my Canon 100mm F/2.8L IS Macro doesn't physically accept my Canon 1.4x III Extender (teleconverter), I bought (from TP Classified) a Kenko 1.4x DGX Pro300 teleconverter as an occasional option for my macro lens - Good on Bees or those others which don't allow you to get too close. The presence of my mounted Kenko is not reported in the image data but the focal length of 140mm is reported. But most of you knew that already :D
 
My pal has one that shows up when used it on his 400f5.6 on his 7dii but isn't showing up on his 70-300L on the 7dmkii
I can't figure this out, it's the Kenko pro 300 1.4 that he's using.
 
exif on this picture from last week shows the correct information, max aperture is f/4
registers as 280mm
sigma 70-200 f/2.8, plus kenko 1.4x DGX pro thingymajig
F/8 1/250s, ISO100, heavily cropped
 
Icee said:
My pal has one that shows up when used it on his 400f5.6 on his 7dii but isn't showing up on his 70-300L on the 7dmkii
I can't figure this out, it's the Kenko pro 300 1.4 that he's using.
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....I have the same combo of Canon 400mm F/5.6L on 7D Mark II and I have both Kenko 1.4x DGX Pro300 and Canon 1.4x III.

My Canon 1.4x reports its presence as you would expect (although it limits the AF pt area options to 5pt maximum) but I haven't tried my Kenko 1.4x on the Canon 400mm so far.
 
DizMatt said:
also I've found out that technically my kenko is not compatible with the sigma lenses, only canon/nikon and tokina.
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....Then, if I have understood your posts correctly, that Kenko-Sigma incompatibility may be why you have the issues you first reported. I suggest that it's struggling to maintain the information it needs to operate the shutter's fps smoothly. I don't know the technical reasons why but I think it's logical.
 
oddly its screw drive lenses that accept a non reporting tc best in my experience, ssm/hsm types hunt more

thats with a77 and kenko 1.4
 
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