Re-thinking focusing modes.

[Jonathan Levin]

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Hi all.

Up until today, I thought I'd never use any focusing mode on my SL3 other than AFs. After cleaning my sensor using the Giotto Medium blower, I started to experiment a bit with a couple of the other focus modes.

First I wanted to try Manual focus. I could see using this mode in the way I used my M's for years when shooting from the hip (i.e.) just holding camera without actually using viewfinder. With the 24-90, this is a little more confusing. Setting the focus for 36" @ 35mm ~f/18 was what I was after. My sleeve length is 36" so that helps me gauge how far camera to subject roughly.

Since there are no actual markings on the lens itself, you have to rely on the little top display on SL3: Front, Focus, and Back. I understand the concept here. Focus is the focus point, and front and back are what the focus range (depth of field) is at a particular f/stop. So I decided to test this and noticed that at the same focus point, changing the f/stop from widest to smallest aperture did not change the front and back focus (depth of field) on top display much if at all. And yes I am in Manual shooting mode.

This made me wonder if there is a bug or if it's me!

I then started to think about AFc focus mode and played around with that for a bit. And I kind of like that mode after all! I like that as long as you hold shutter release part way, focus continues even as you move camera around, and I'm hoping if people are in my photo it is quick enough to snap focus if there is some people movement.

Now I am confused as to which I like better, AFs or AFc. So your preferences and why? Look forward to your thoughts. Jonathan

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[jaapv]

It all depends on what you are photographing.There is no single setting. 

[Chuck Albertson]

At that close a focusing point, you won't see a huge change in depth of field. Leica doesn't publish depth-of-field tables for the 35 SL lenses, but if you download the data sheet for one of the 35 Summicron M models, it's pretty well illustrated. Try 6' or 10' out.

[Photoworks]

4 hours ago, Jonathan Levin said:

Since there are no actual markings on the lens itself, you have to rely on the little top display on SL3: Front, Focus, and Back. I understand the concept here. Focus is the focus point, and front and back are what the focus range (depth of field) is at a particular f/stop. So I decided to test this and noticed that at the same focus point, changing the f/stop from widest to smallest aperture did not change the front and back focus (depth of field) on top display much if at all. And yes I am in Manual shooting mode.

at minimal distance you will find some lenses don't have much DoF.

I set my M lenses to a 2-5 meter range.

But I don't see a bug, if you take a photo you can measure how much is in focus.

with 24-90 at 35", you get the same result on SL2 and SL3.

the calculation is always reasonably perceived sharpness

 

 

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[Dr. G]

I do a fair amount of hand held closeup work.  When working close up, yes, depth of field becomes really narrow.  Even in AF-S I could end up moving slightly forward or backward while releasing the shutter.  With the SL3 I've pretty much kept the camera in AF-C for those types of shots.  

 

But I agree with @jaapv - there is no one setting for everything.  Even in choosing the focus area you use (spot, field, etc) you'll find different results in different scenarios.

[hdmesa]

On 9/6/2024 at 3:07 PM, Jonathan Levin said:

...I then started to think about AFc focus mode and played around with that for a bit. And I kind of like that mode after all! I like that as long as you hold shutter release part way, focus continues even as you move camera around, and I'm hoping if people are in my photo it is quick enough to snap focus if there is some people movement.

Now I am confused as to which I like better, AFs or AFc. So your preferences and why? Look forward to your thoughts. Jonathan

AFc is all but necessary with eye-AF when photographing people at headshot distance with wide aperture lenses shot wide open – otherwise small movements of both the model and the photographer's can cause misfocus on the eyelashes or an eyebrow. Hit rate on the iris of the eye goes from about 50% with AFs to around 85% with AFc.

Edited September 8, 2024 by hdmesa

[LocalHero1953]

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Much of the time I use iAF with Face/Eye AF. That way it uses AFc when it sees, as a minimum, a body, but defaults to AFs Field when it can't even see a body.

[hdmesa]

4 hours ago, LocalHero1953 said:

Much of the time I use iAF with Face/Eye AF. That way it uses AFc when it sees, as a minimum, a body, but defaults to AFs Field when it can't even see a body.

The problem I run into with using anything eye-AF for non-human scenes is it will find faces in things that are not faces about 1 out of every 5 scenes. Seems to happen the most with busy background shooting wide open — the bokeh shapes often get interpreted as faces.

[LocalHero1953]

6 hours ago, hdmesa said:

The problem I run into with using anything eye-AF for non-human scenes is it will find faces in things that are not faces about 1 out of every 5 scenes. Seems to happen the most with busy background shooting wide open — the bokeh shapes often get interpreted as faces.

Strange - not doubting you, but not something I've encountered - I'll watch out for it. It does seem sometimes focus on the closer head, even if that is turned away i.e. it chooses the back of the nearer head rather than the further face.

[Dr. G]

17 hours ago, LocalHero1953 said:

Much of the time I use iAF with Face/Eye AF. That way it uses AFc when it sees, as a minimum, a body, but defaults to AFs Field when it can't even see a body.

I always forget about iAF.  I may need to explore this more.

[LocalHero1953]

1 minute ago, Dr. G said:

I always forget about iAF.  I may need to explore this more.

I'm not convinced I know exactly how it works, but it appears to be a a handy AFs/AFc compromise.

[hdmesa]

8 hours ago, LocalHero1953 said:

Strange - not doubting you, but not something I've encountered - I'll watch out for it. It does seem sometimes focus on the closer head, even if that is turned away i.e. it chooses the back of the nearer head rather than the further face.

It does happen to me more in regular face/body detection mode than iAF mode. iAF seems a little less aggressive. I wish for both we could have a slider adjustment for how hard it looks for a face. Even a slider adjustment for size of the face would be helpful. I'd love a setting that only identified faces when they are at closer distances.