07-15-2010, 03:21 PM
[quote name='zz7' date='15 July 2010 - 11:37 AM' timestamp='1279186653' post='1019']
Thanks for this post. I do not see much sense arguing over your statements, all this makes sense.
However, let's simplify discussion to following situation: let's assume that I shoot only landscapes on infinity focus. Would not the manual focus lens (where focus ring turned to the edge means infinity) simplify my life and reduce number of technically flawed images (due to autofocus errors)?
Thanks,
Alex
[/quote]
Hi Alex,
In that case, why not settle for fixed-focus lenses?
This really defeats the object of a lens with any focusing mechanism at all.
AF is not necessarily flawed, no more than manually focusing a lens. It is all about knowing how to work the AF, know its limitations, just like you need to know your own limitations when focusing manually on a focusing screen. I dare say that under most circumstances, AF is better than MF, and certainly faster. However, what I do see a lot is that people when doing portraits, focus, f.e., on the ridge of someone's nose in a frontal head shot, IOW, on an area with no contrast whatsoever, especially when the light gets a little dimmer. This never worked well with MF, so why should it work with AF, when it all is really contrast or phase based. Do focus on something with a bit more of a contrast transition, e.g., an eyelid, which has eye lashes, and underneath there are the white areas of an eye. That's a lot easier to focus on, both manually and automatically, and the added bonus is that this is exactly what we humans expect to be sharp in focus, the eyes.
Other than that, have you ever tried MF? How often did you overshoot and have to turn the lens back, in either direction, and how many times did you have to do that? AF is way faster in this regard.
As I said, you just need to know how to use it, and that requires experimentation.
Another thing when it comes to landscapes: why would you ever want to focus at infinity? That is essentially the wrong thing to do, as you lose a lot of DoF in the foreground that way, and beyond infinity there is no need for extra DoF. Concentrate on that which is what attracts your attention in a shot, and focus on that, i.e., about 1/3 into that object, 1/3 being in front of the focus point, 2/3 behind it. That was a good rule of thumb from the analog period that still works with digital. It guarantees that that which attracts the most attention in a photograph, is imaged sharply and really becomes the point of focus, under all circumstances. Unless you use an extreme wideangle, and even 21 mm on FF is not enough in this regard, it is not possible to have everything in focus at apertures you'd like to use anyway. Sharpness as a function of DoF doesn't pan out as tables or calculators tell you, unless you do only tiny prints. Unlike what a lot of people think, sharpness in DoF is a gradual transition, not a set of boundaries between which everything suddenly is sharp, although a low MP camera (< 6 MP in APS-C) may make it look that way.
This gradual transition is the exact reason why you do have to focus, otherwise it wouldn't matter.
Kind regards, Wim
Thanks for this post. I do not see much sense arguing over your statements, all this makes sense.
However, let's simplify discussion to following situation: let's assume that I shoot only landscapes on infinity focus. Would not the manual focus lens (where focus ring turned to the edge means infinity) simplify my life and reduce number of technically flawed images (due to autofocus errors)?
Thanks,
Alex
[/quote]
Hi Alex,
In that case, why not settle for fixed-focus lenses?
This really defeats the object of a lens with any focusing mechanism at all.
AF is not necessarily flawed, no more than manually focusing a lens. It is all about knowing how to work the AF, know its limitations, just like you need to know your own limitations when focusing manually on a focusing screen. I dare say that under most circumstances, AF is better than MF, and certainly faster. However, what I do see a lot is that people when doing portraits, focus, f.e., on the ridge of someone's nose in a frontal head shot, IOW, on an area with no contrast whatsoever, especially when the light gets a little dimmer. This never worked well with MF, so why should it work with AF, when it all is really contrast or phase based. Do focus on something with a bit more of a contrast transition, e.g., an eyelid, which has eye lashes, and underneath there are the white areas of an eye. That's a lot easier to focus on, both manually and automatically, and the added bonus is that this is exactly what we humans expect to be sharp in focus, the eyes.
Other than that, have you ever tried MF? How often did you overshoot and have to turn the lens back, in either direction, and how many times did you have to do that? AF is way faster in this regard.
As I said, you just need to know how to use it, and that requires experimentation.
Another thing when it comes to landscapes: why would you ever want to focus at infinity? That is essentially the wrong thing to do, as you lose a lot of DoF in the foreground that way, and beyond infinity there is no need for extra DoF. Concentrate on that which is what attracts your attention in a shot, and focus on that, i.e., about 1/3 into that object, 1/3 being in front of the focus point, 2/3 behind it. That was a good rule of thumb from the analog period that still works with digital. It guarantees that that which attracts the most attention in a photograph, is imaged sharply and really becomes the point of focus, under all circumstances. Unless you use an extreme wideangle, and even 21 mm on FF is not enough in this regard, it is not possible to have everything in focus at apertures you'd like to use anyway. Sharpness as a function of DoF doesn't pan out as tables or calculators tell you, unless you do only tiny prints. Unlike what a lot of people think, sharpness in DoF is a gradual transition, not a set of boundaries between which everything suddenly is sharp, although a low MP camera (< 6 MP in APS-C) may make it look that way.
This gradual transition is the exact reason why you do have to focus, otherwise it wouldn't matter.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....