AF-S to AF-C quick change. Is it possible ?

[ArendV]

Thanks Erik for the references, will have a look at them later !
(and then it will take me even more time to digest having quickly looked at the second link  )

[Erik Lund]

Second link is actually very interesting where Marianne clearly show the AF module design and reverse engineer it; She shows why there is no difference in AF performance between a f/1.4 and a f/5.6 lens,,, and the AF f/5.6 and F/8 restrictions Nikon always states are clearly unveiled, they are simply dimensional restrictions of the AF module itself!

A very good read for the technically inclined

[Ilkka Nissilä]

I find that f/2.8 lenses in general autofocus much better than f/5.6 lenses. On the D5, f/5.6 only give a handful of cross type points, and on some f/4 lenses there is also a restricted list of cross type AF points available (as well as a few f/2.8 lenses). f/2.8 lenses typically autofocus more reliably than lenses of other maximum apertures, I would say empirically that the AF system behaves as if it were optimized for f/2.8 lenses. I haven't studied the theory of it though, it is just practical observation.  I have a few individual lenses (such as the 20/1.8 ) which are faster and autofocus better than f/2.8 lenses (the 14-24/2.8 ) but in most cases going from f/2.8 to f/2 and f/1.4 is with a lot of pain and fine tuning. Thankfully Nikon has automated that in the latest two high end DSLRs, so at least a starting point value can be reached easily, even if it has to be verified and sometimes adjusted based on real world use.

My experience is that AF-S cannot be trusted  so many years ago I stopped using it completely (apart for some testing situations), but cameras have improved since and perhaps this goes for AF-S mode as well. But I remain an AF-C user and prefer it.  I cannot stand the camera deciding when to stop focusing; it's my call to make.

[armando_m]

I have good results with my D800 in AF-C + AF button

If I'm using big apertures, I rather move the focus point to the correct spot , vs focus and recompose as I often will not get the right focus

I do not use AF-S

[Erik Lund]

I find that f/2.8 lenses in general autofocus much better than f/5.6 lenses........

Well I have always had the same feeling, but for sure the series of 2.8 lenses are generally of a very high standard and has the best AF-motors build in.

But none the less the way the AF moduel is designed it treats all lenses below f/5.6 the exactly the same, it is not the case that 'more light' enters the AF module from a f/1.4 lens than a f/5.6 lens - Simple as that.

Actually the aberrations of found in fast glass on the faster 1.4 lenses makes the focusing harder for the AF module,,,

[David H. Hartman]

But none the less the way the AF moduel is designed it treats all lenses below f/5.6 the exactly the same, it is not the case that 'more light' enters the AF module from a f/1.4 lens than a f/5.6 lens - Simple as that.

If the AF module limited in the same way an R screen for an F2 or F3 is limited in its accuracy because of the angle it can see through a slower f/3.5~5.6 lens? Are some of the segments of the AF module looking at the lens barrel on an f/5.6 lens so they cannot contribute to focus?

Dave

This is probably an ignorant question as I've never read much on how the AF modules function optically.

[Ilkka Nissilä]

Multi CAM 20k has restrictions on f/5.6, select f/4 and at least one f/2.8 lens (60 Micro, possibly because it becomes slower at close focus) as to which of the 99 cross type sensors function as cross type so this seems similar to Canon's earlier models where cross type or double cross type is only available on f/2.8 or faster lenses. The details are in the D5 manual.

Anyway it is clear that in practice f/2.8 lenses AF better than f/5.6; whatever the technical reason may be. There must be an explanation even if it has nothing to do with the quantity of light the AF sensor sees.

[Erik Lund]

Please just follow the second link for further information - Thanks

[Frank Fremerey]

I like to see a NG-workshop on AF technicals and techniques in the future of NG, held by someone who really knows what he/she  is talking about like Ilkka

[simsurace]

I'm curious: has the OP's question been answered?

[Erik Lund]

Yes it has, and answer is: No I can't.

[simsurace]

I ask because reply #13 looks like the right answer to the question, but the OP has never said that he is satisfied with this answer.

[Ilkka Nissilä]

I like to see a NG-workshop on AF technicals and techniques in the future of NG, held by someone who really knows what he/she  is talking about like Ilkka

Ulp, I wonder about the last part.   

A focusing workshop  could actually be interesting. It could cover topics such as
- general theory of focusing, AF, MF, different camera features including pattern recognition
- autofocus from a wildlife photographer's perspective (volunteers?)
- autofocus in people photography (sports, weddings, portraits etc.)
-  fine tuning / microadjustment of autofocus in DSLRs

Another day could focus on
- manual focusing using OVF, EVF, LV
- techniques to extend near-to-far sharpness: focus stacking and tilt
- focus in UV and IR photography (?)
- creative use of focusing and shallow depth of field

The location should be such that stuff is happening and AF use can be practiced on a variety of subjects. The manual focus section could be at a landscape location or e.g. garden or forest, a location which is conductive to a slow photography approach. 

Sports events can be problematic in that often photography is restricted by the organizers. Also for the sake of creativity it would be nice that people can move about to find their own subject and vantage point.

I think outdoor festivals such as carnivals, or other types of festivities can be excellent subjects where AF can be used and public photography is common and welcomed by the subjects / performers in general.

However, the "slow photography" (i.e. practice of manual focusing, focus stacking, creative focusing) part would likely have to be a totally different location.

I'm always keen on exploring new locations and events.

Anyway just my thoughts on the topic.

[ArendV]

Sound interesting Ilkka, I will sign up (depending on timing and locations) !

[Ilkka Nissilä]

I was just expressing thoughts, not that I would organize it ;-) But maybe someone can. I think nikongear members would be able to give excellent specialist talks on some of these topics. Also I think that it would be great for sharing ideas.