The AF sensor looks through the lens in a similar way (although via a mirror) and it works by looking at a beam of light from the left hand edge of the aperture and another beam from the right hand edge. F/5.6 always looks a certain size, f/4 is bigger and f/8 is smaller. The f-number tells you how big the aperture (or more strictly the "exit pupil") will appear to be, as seen from that position. Imagine yourself as a tiny creature sitting in the middle of your sensor, looking forwards through the lens.
#Dgx digital video camera manual
and manual focus through an f/11 lens (especially with a crop camera viewfinder) is pretty difficult. You might get away with the 1.4x (f/8) but the 2x gives you an f/11 lens. The Kenko bypasses the camera's ability to disable AF above f/5.6 but it can't make the AF sensor work any better than it was designed to. Apart from IQ issues, you will struggle with focusing. In addition, as other posters have pointed out, the Canon 100-400 f/4.5-5.6L lens doesn't really perform well with extenders. f/11 is pretty dark, so pretty hard to manually focus. If you put a 2X extender on a Canon 100-400 f/4.5-5.6L lens, you get an 800 mm f/9-11 lens. The less light you have, the harder it is to see if the image in the viewfinder is sharp or not, which is how you have to manually focus. Canon lenses report their maximum aperture to the camera and if it's smaller than f/5.6-which is what would happen if you put an extender on the 100-400 mm Canon lens-the AF is disabled.įor manual focus, you need light. I think it has to do with the geometry of the light circle and the sensor. Anyway, although I don't understand the technicality of this, the practicality is that the AF on a crop-sensor Canon camera works poorly if at all at smaller maximum lens apertures than f/5.6. We probably should talk about "below f/5.6," because we're talking about a smaller aperture than f/5.6. So while test chart shots in ideal conditions will show a definite benefit from using the TC, in the real world the practical difficulties tend to negate this. And camera shake is twice as bad with a 2x TC.
#Dgx digital video camera iso
AF simply won't function, and manual focus through an f/11 lens (especially with a crop camera viewfinder) is pretty difficult.Īnother point to bear in mind is that being limited to f/11 will mean using a slower shutter speed and /or a higher ISO speed to compensate, either of which can affect image quality. "Stay away from the Canon" seems pretty strong given that they are optically excellent and better built than the Kenko, but the Kenko does have some practical advantages - no need to tape pins and it fits any EF lens - and of course it costs much less. If you've already researched this and you know that there will be issues but still want to go ahead, then the Kenko DGX is a good choice. I would consider either the 1.4x or the 2.0x. There appears to be some good words for Kenko DGX.
The reviews I have read basically suggest I stay away from Canon. I realize there will be some issues associated with an extender, but would still like to extend the range on my 100-400L USM lens. I have a Caon 60D and would like to get an extender. Hi Guys: I always get good advice from this forum, so here is another request. I found the 1.4x was useful many times but not always. In my film days I carried both 1.4x and 2x TCs with me in my bag but over decades I could count the number of times I was willing to put up with the reduced IQ of the 2x on the fingers of one hand, even when using a 300/2.8.
That is so the effective maximum aperture is no worse than F5.6 which is well within the camera's abilities. Remember TC s are designed to be used on either F2.8 lenses (1.4x and 2.0X) or F4 lenses (1.4x only). Personally the 100-400 is not great at 400mm(it is good however) and adding a TC will make it worse in all cases, with a 2x being the worst of all. It is limited to F5.6 (although F6.3 will work).
#Dgx digital video camera pro
Even with a 3rd party TC the 60D will not AF reliably even with a 1.4x TC because the effective f-ratio will be F8 and the 60D unlike some of the pro bodies does not have AF sensors capable of AF at F8. Well the Canon TC will give you better optical performance but in many cases will not allow you to do AF, which admittedly will be very marginal anyway (that is where taping the contacts can make it AF).