Will the New 5D AF at F8?

[dk.]

With respect to using teleconverters on a lens like the 400mmF5.6L

or others pushing the F stop up to F8. Does anyone know if the new

5D can still focus at F8 like the 1D II can? Or is it the same as

the 20D and stop AF at F5.6. I would like to know. Thanks.

 

DK.

[PuppyDigs]

On a side note, my EOS 3 has the many fabled 45 sensor AF array and will AF at F8.

However, it degrades to one single axis sensor and won't lock onto much of anything.

I find MF more reliable at F8.

[tim_adams]

No it will not.

[dk.]

Cheap bums! lol

 

You would think they could have included that since everything is bigger and better i.e. the viewfinder/sensor etc gathering more light then the 20D for example, and make it work really good too.

If I get a newer camera Body in the future, I would like it to be able to do this as I ware glasses and am not the fastest at focusing with wildlife etc. Thanks for the response's

 

DK.

[mark u]

Although the camera firmware disables AF when it gets a report of a maximum aperture narrower than f/5.6, it's quite likely that using a taped Canon TC or a Tamron TC (which will cause the camera to consider the aperture to be the same as without the TC) that focus will still work. Of course, real life testing will be needed to prove the point either way.

[steve_dunn2]

<p>The 5D's AF system is derived from that of the 20D, which is designed to work only to f/5.6. Only the central AF point of the 45-point bodies (3, 1V, 1D family) is designed to work at f/8.</p>

 

<p>It will probably work somewhat beyond f/5.6 as long as it doesn't know the lens is that slow; quite a few third-party telephoto zooms are slower than f/5.6 on their long ends, but they lie to the body, and AF works. Will it work at f/8? Maybe, maybe not, but almost certainly not reliably. I haven't tried it on my 20D. I did try this once on my Elan 7E, and found that the answer was basically no. It might work occasionally, but most of the time, the AF system would hunt back and forth without ever locking onto the subject (even with a subject which it would quickly acquire with the same f/5.6 lens without TC).</p>

[mark u]

The difference between the central AF point on the Elan 7E and that of the 5D is that the latter has a high precision double cross sensor, which gives AF a lot more data to work with. The same is true of the 20D - and the evidence of this thread:

 

http://forums.dpreview.com/forums/read.asp?forum=1019&message=10927692&changemode=1

 

is that AF works at f/8 on the 20D so long as the camera is fooled into not recognising the actual effective aperture in use.

[byronlawrence]

well the center point is the only point worth a %#&(#*^. whether you are tracking something or focusing and recomposing it is usually the most versatile and the most sensitive. the rest are just fluffers. :)

[steve_dunn2]

<p>The high-precision central sensor is irrelevant to AF at f/8, since it only works at f/2.8 or faster. If you were to take an f/2.8 lens and add a 2x and a 1.4x, without the body knowing about them, then the high-precision sensor would remain active, though it probably wouldn't help much if any because it wouldn't be getting the light it needs. But using a slower lens like the 400/5.6L, even with a TC that the body can't detect, there is no high-precision sensor available.</p>

 

<p>I just tried my 20D, 28-135/3.5-5.6 IS USM, and 1.4x II. Standard disclaimer applies: if you're not careful, the rear element of the 28-135 <em>will</em> strike the front element of the TC, potentially damaging either or both, and that could be quite expensive, so don't try this at home.</p>

 

<p>At the long end, this combination is f/8. I manually selected the central AF point and found that it worked very much like doing the same thing on my Elan 7E: it would usually get close, then hunt back and forth without ever actually succeeding. Once, I did manage to find a very high-contrast target it would acquire successfully. With medium-contrast targets, if I manually focused and then activated AF, it would agree that the target was in focus. If I manually misfocused slightly, AF would hunt back and forth. Without the TC, this body and lens have no problem locking onto these. Low-contrast targets didn't work at all; again, without the TC, this body and lens have no problem locking onto these.</p>

 

<p>So both the Elan 7E and the 20D <em>can</em> autofocus at f/8, but only in limited situations. I wouldn't suggest that one should count on this combination.</p>

[mark u]

I'm not sure that you can draw a valid conclusion testing with a lens that isn't designed for use with a TC in the first place that probably produces very soft images when used in that way. Then it would be no surprise that the AF system struggles to find focus given there is no point at which it is truly sharp to begin with.

[dk.]

Mark U, Thank you for that link above, I learned something from reading all of it (About parameters) and hope to take better pictures because of it.

And thank you to all others that responded here too.

 

DK.

 

 

P.s. By the way If I was ever to tape the conections on a TC which ones would I have to tape and which ones to leave alone?

[jwhyche]

Can someone explain this to me? I've put the Canon EOS-5D on my to buy real soon list. My only experience is with Nikon camera's, specifically the D70. From what I read here I'm getting the ideal that Canon camera's can't AutoFocus through the entire aperture range. Is this true?

[dk.]

No, it can focus on any lens at any Aperture as long as the first/largest Aperture value on that lens is F5.6 and down etc F5.6, F5, F4.5, F3.5, F3.2, F2.8 and on.

 

Lets say you bought a lens that's largest aperture value was F8 (it would be hard to find, if there is such a thing, I don't know and who would want a lens that started at that anyway. lol) but if that was the largest Aperture on that lens then well this camera would not focus with that lens at all, period.

 

So with using Canon TC's on the end of a lens it makes the camera body think you have a lens that's largest Aperture is smaller then it really is, in this case F8 (400mmF5.6 plus 1.4TC =F8, I think) and so it will not focus for you if it starts at F8 so you have to focus manually.

 

So as long as your lenses largest aperture starts at or below F5.6 with this Body which they all do as far as I know. You are fine and it will focus at any aperture thru the whole range on that lens all the way up to F22, and on. Its when you want to Use TC's you have to look out if you want AF depending on the lens and its Aperture etc.

I hope that answers your question and did not make you more confused Jeff.

 

 

DK.

[mark u]

Jeff - all autofocus is done with lenses at their widest apertures on both Canon and Nikon cameras (and all other manufacturers' bodies too). Any aperture that is set for actual exposure has no impact - the camera stops down the lens immediately before the shutter opens (while the mirror is rising) and opens it again as soon as the exposure is complete (while the mirror is dropping back into position. All modern SLR AF systems rely on a principle that was originally patented by Honeywell (who collected over $200m enforcing the patent against camera manufacturers).