Chip for MF Lenses

tiha,

tiha wrote:

Or maybe camera works much simpler, in which case there is really no reason for Canon to disable it (except market reasons of course ).

I think you are barking up the wrong tree with this.

I have just tried a selection of lenses in MF mode on a couple of Canon DSLR bodies and without exception they all give focus confirmation in the viewfinder. So what is your beef about no MF focus confirmation?

Is it that Canon disabled it for third-party lens adapters used with lenses which were designed and made before there even was a Canon DSLR on the market?

If the latter then I think that you are way out of order and need to get back into reality - the point is that the camera NEEDS the information from the lens before it can assess correct focus (either AF or MF) and by definition MF lenses, especially those from other manufacturers mounted on an adapter DO NOT have the chip to provide this!

The German MF chip is designed to solve this lack of the relevant chip on MF lenses and adapters.

Sigh..............

Of course. All the time we are talking about using MF lenses with adapters: M42, Leica, Nikon etc. When they'are used there is no focus confirmation. And of course it works with Canon Lenses in MF mode

Camera probably needs that information to determine DOF and when to lit confirmation LED.

Yes, but if camera really needs accurate information about lens, chip can provide information only for one type of lens (auhor stated that it is made like 24-70mm F2.8 lens) and focusing confirmation may be inaccurate.

I've just found confirmation (at another forum) that the chip reports lens data as aperture F2.8, focal length 24-70mm set to 50mm. User said that it works perfect with his 50mm F1.4 lens - only care should be taken not to move focusing ring too fast when near focusing point

"Yes, but if camera really needs accurate information about lens, chip can provide information only for one type of lens (auhor stated that it is made like 24-70mm F2.8 lens) and focusing confirmation may be inaccurate."

You are likely to be making too much out of your ideas about WHY it can't/shouldn't/mayn't work.
Why does camera need information about the lens to achieve focus - focus is either right (in focus) or wrong (out of focus)?
DoF has nothing to do with it . DoF in this case is only useful for the human eye to judge whether the focus is acceptable or not. I agree that Canon consider AF accuracy to have to be +/- within the DoF but when you are manually focusing the confirmation light is only intended to be a guide - and is right more often than not, but is always subject to the same inaccuracies as the AF system.
Get away from the obsession of the 24-70/2.8L being used to gauge the protocol across the camera/lens interface - that was most likely what he had to hand which was up to date and an L lens, any Canon lens would have done in all probability.

In any case I'm interested because I need to fool the camera into actually working with a certain set-up and this chip may well be the answer - focus confirmation being a welcome bonus.

tiha wrote:
I've just found confirmation (at another forum) that the chip reports lens data as aperture F2.8, focal length 24-70mm set to 50mm. User said that it works perfect with his 50mm F1.4 lens - only care should be taken not to move focusing ring too fast when near focusing point

Which other forum tiha?

If camera "thinks" that lens is 50mm, but lens used is, let's say, 300mm I believe there is high probability that user will get wrong focus confirmation and camera will misfocus. My point is if camera gets wrong data, whole system will be even less acurate than with AF lens in MF mode.
Device isn't cheap and many users intent to use it with longer telephoto MF lenses which are very expensive in Canon EF version and they may be dissapointed. It will work great for focal lengths about 50mm - but users who need this range probably have already bought either EF 50mm 1.8 or EF 50mm 1.4. On the other hand, users with wide angle lenses will probably get excellent pictures
Device is still new on the market and only time will tell if it is worth buying. At this time we just need more feedback.

http://forums.dpreview​.com …rum=1029&messag​e=16296162

Discussion started about focusing with split prism screen, and somewhere in the middle someone mentioned this chip.

There was a thread in FM forums, unfortunately I can't find it anymore, where a user stated that actually the AF system of the camera does not need any information from lens. No focal lenght, no aperture, no anything. Those things did cancel out in formulas, so he said. He was surprised, too. IIRC he said that based only on the phase difference of the AF sensor pair (plus few things that are constant for given camera) the AF system can tell the lens how much and to which direction to move the focusing element. Sorry for posting such vaguely supported information, but to me it was fascinating.

It obviously makes sense. If the focal length and stuff were having any impact, it would mean that rangefinder or prisms wouldn't work.
The only thing that impacts the AF or the focusing with prisms and other in-lens focusing aid is the maximum aperture.

The AF focus confirmation is "binary"; on or off, so it indeed means you have to focus very slowly just to register that the LED is on. Which makes it pretty much useless. Now prisms/microprisms screens shows you *exactly* on an analog scale the mount you have to turn the focus ring. Quite a difference to me.

This is certainly true. I have no idea why Canon decided not to provide the feature, but others have. I get focus confirmation with adapted manual lenses on my Pentax 645N and NII, and I'm mighty glad to have it. Of course, the 645 accepts a range of non-autofocus lenses made by Pentax, so they really had no choice. But it works and it works very well. Canon could easily have provided the feature had they chosen to, but I seriously doubt that it was in their design requirements to accommodate old M42 lenses adapted to the Canon mount, and unlike Pentax they had no stock of non-AF lenses they were trying to accommodate.

Rick "who will experiment with these when they arrive from Germany" Denney

Look forward to seeeing your results and comments Rick.