MF Override for pre AF-S lenses
I had a sort of D'OH moment the other day. It concerns my several screw drive lenses and quickly changing to MF to get the lens in the ballpark whenever the detail I want to focus on is not what the camera thinks I should have in focus. Yes, one can easily enough get to the AF-MF lever arm and it's also easy enough to learn the motions but one has to pull it out for MF and push it in for AF and these motions don't come naturally with the viewfinder up to the eye. What if, thought I, one were to simply press the lens release button, bring the focus back to the small detail the camera refused to consider, release the lens release button and autofocus once more. I've done this successfully a few times and it seems like a keeper but...
The question I have is whether anyone else has experience with this and, additionally, whether there are only good things to say about the behavior or whether there are any horror stories. Cursory searching of the archives did not turn anything up.
#1. "RE: MF Override for pre AF-S lenses" | In response to Reply # 0
#2. "RE: MF Override for pre AF-S lenses" | In response to Reply # 1Mon 14-Oct-13 03:47 PM
That hadn't occurred to me, thanks. However, the motion necessary to part the camera from the lens is so large and complex that I would never attempt it with the camera up to my eye so, with respect, I believe the possibility to be sufficiently remote to justify discounting it. YMMV
I am more worried by the possibility of damaging the camera by wrenching the camera screw drive around with the lens focus ring. This would seem to take care of that. Any experiences to share?
#4. "RE: MF Override for pre AF-S lenses" | In response to Reply # 2blw Nikonian since 18th Jun 2004Tue 15-Oct-13 06:10 AM
Well, my advice is, shall we say, hard-earned. It's not so much the moment you're doing this as the time you don't quite get it locked down again - and then it happens when you are least expecting it. In my case the problem occurred because I had big thick gloves and I was not being sufficiently careful, but the point is that I unlocked the lens release and ten minutes later I had the lens come off in my hand. Fortunately it didn't fall into the Merced River, but it was just luck that it didn't.
Brian... a bicoastal Nikonian and Team Member
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#3. "RE: MF Override for pre AF-S lenses" | In response to Reply # 0
I'm not surprised you haven't found any information about this technique here - as Brian says, it sounds like a recipe for potential disaster to me!
In any event, it would not work with ALL screw-drive AF lenses - some of them have their own AF/MF switch which locks the focus collar unless switched to MF.
#5. "RE: MF Override for pre AF-S lenses" | In response to Reply # 3Tue 15-Oct-13 02:04 PM
>I'm not surprised you haven't found any information about
>this technique here - as Brian says, it sounds like a recipe
>for potential disaster to me!
>In any event, it would not work with ALL screw-drive AF lenses
>- some of them have their own AF/MF switch which locks the
>focus collar unless switched to MF.
Fair enough. I now notice that the 105 f/2.8D micro has the focus collar disengaged when set to AF and that, for such a lens, the technique would indeed not work. Thank you for pointing that out. As it happens, even with the focus limiting feature, this lens often still hunts so I end up using it in MF most of the time, anyway. Once the image is framed the point I want in greatest focus is not always conveniently under a focus point at which point Live View really comes into its own.
That said, let me outline the scenario I have in mind, taken from recent experience. Camera, D600: lens 24-85 f/2.8-4D set to "macro". Camera supported on a monopod, framing a rather sparsely populated fern, aiming straight down, focus point on the fern stem which is approximately half the distance from the camera as the ground beneath and very, very skinny, oriented diagonally through the center (cross) focus point. The monopod serves to remove one source of focus error - aging back muscles. But, because it doesn't remove rotational error, along with tiny wind shifts, it is still difficult to stay on the stem and often the camera (quite sensibly) chooses the ground as the more reliable target, at which point the AF loses all hope of re-acquiring the stem which has become a hopeless blur. As with most screw drive AF lenses, when the drive is disengaged the focus ring exhibits almost no drag and therefore presents a negligible danger that carefully manipulating it (and it alone - this is a source of danger but, it seems to me, still acceptably small given the gross difference in necessary effort and motion) will dislodge the lens from home. The final step, after reorienting the lens to the general focus distance I am after, is to re-acquire focus on the stem via AF, which is likely to be more accurate than I can manage with the viewfinder anyway, and which will also serve as a check that the lens is still home, locked and safe. As I say, I have done this on a few occasions and it seems to work - for me.
Now, allow me to argue against my own proposal on practical, rather than theoretical, grounds. The AF-MF lever is a lever for very good reasons, allowing one to use the thumb to go to MF and the index finger to AF. Even on three-position levers (e.g., D300) it is possible to quickly switch and lock focus mode settings, freeing the left hand to grab the focus ring. That is, if you can find the lever - for most of us it's one of those set and forget items. The scheme I am proposing has as its chief practical drawback the necessity to maintain pressure on the lens release button with the left index finger while using the right hand to focus. My guess is that for most folks this feat of ambidexterity alone will have been found sufficiently difficult to master to have discouraged most attempts. In the example above the monopod helped control the camera. Still, like some of the doohickeys of specific but limited usefulness that inhabit the bottom of the camera drawer, every once in a great while this might be a technique to trot out when it will prove to be the shortest path to the desired result.
#7. "RE: MF Override for pre AF-S lenses" | In response to Reply # 5TBerryhill Registered since 16th Jan 2013Tue 15-Oct-13 08:19 PM
Just for the record, are you saying that just the act of depressing the lens release button without any lens rotation disengages the AF screw mechanism and thus allows you to freely rotate the MF ring? Given the considerable torque necessary to start the lens from its locked position it sounds like a safe enough procedure for one with his wits about him. If I ever acquire an AF lens I will keep it in mind. Tom
#9. "RE: MF Override for pre AF-S lenses" | In response to Reply # 7Tue 15-Oct-13 09:09 PM
> Just for the record, are you saying that just the act of
>depressing the lens release button without any lens rotation
>disengages the AF screw mechanism and thus allows you to
>freely rotate the MF ring?
That is indeed the case. To the eye, the release button disengages the screw drive in exactly the same way that the focus mode button does. Otherwise, none of us would ever be able to dismount our pre AF-S autofocus lenses. Dismount a lens and have a play with both buttons. Looking at the F mount from the front, the drive is at ~8:00. My concern is for non-visible dis-similarities that could lead to internal damage. I cannot think of any, especially since the movement is confined to the lens. Given the evolutionary nature of the internal motor AF system, the necessity for it to accommodate all previous AF lenses and its apparent developmental dead end at the millennium with the appearance of AF-S, it is easy enough to believe that things were simple then and have stayed so. But belief does not equal reality. I am seeking evidence based on experience or firm knowledge.
#8. "RE: MF Override for pre AF-S lenses" | In response to Reply # 5gpoole Nikonian since 14th Feb 2004Tue 15-Oct-13 08:57 PM
If you are doing macro, once you get the lens approximately focused on the critical part of the image, move the camera back and forth slightly to fine tune the focus. This is much easier and faster than manually focusing the lens.
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#10. "RE: MF Override for pre AF-S lenses" | In response to Reply # 8Tue 15-Oct-13 10:40 PM
Agreed - for real macro. But, if you're referring to my presenting scenario, be aware that I put the word "macro" in quotes because this particular lens isn't a true macro and the situation I see it useful for is while on walkabout with a monopod and not a tripod equipped with a focussing rail. I have certainly used the in-out method free hand (courtesy of my back muscles) when shooting approximately level. One can achieve very good results for some subjects. But when attempting a minimal DOF capture of a fern frond, the orientation of the sensor plane to the frond becomes critical and calls for a shooting position that I can neither maintain for very long nor reliably vary to achieve focus except by trying to shoot as the focus is transitioning through perfect (and don't forget those subtle wind shifts!). Just why I was really trying to use autofocus in the first place.
If you're referring to the 105 f2.8D that lives on the D300 that lives on the tripod, then I have found Live View and manual focus to get me where I want to go in most instances. Still, I can't imagine a focus rail is not in my future.
#11. "RE: MF Override for pre AF-S lenses" | In response to Reply # 0
Why don't you just use the lens as a manual focus lens?
Its not as if the lens needs a lot of rotation with the focus ring to get focus.
Much simpler and safer and less chance of doing any damage with the method you are suggesting.
#12. "RE: MF Override for pre AF-S lenses" | In response to Reply # 11Mon 21-Oct-13 03:50 PM
Sure, in a sense. But, as I stated in the premise, it was my belief that in this instance autofocus would be more accurate than my eye in persuading this particular lens into focus. This lens, which exhibits minimal drag at the focus ring with the screw drive disengaged, still demands an amount of starting torque sufficiently different from the effort to move once started, thus rendering it edgy to use as a manual focus lens. It has none of that silky feeling that a good MF lens exhibits. I'm old enough to have used my fair share of those and old enough to know when to trust the camera's AF rather than my eyes. The simple intent of the scheme is to get the lens to a slightly front-focused state, away from the dead zone, so that if the AF goes hunting the wrong way, it won't find a plausible subject in the background and stay grounded there. Which is exactly what it had been doing.
Any evidence, anyone?