Is the focus ring informative?

[Xavi]

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Is the focus ring informative or does it do something?

Let me explain better

If I set the focal length to F/11 with a 35mm, that means I have focus from 1.8 meters to infinity according to the hyperfocal tables

Do I need to change the focus ring to that position?
Or does it matter since it is only informative?

[Xavi]

1 hour ago, Al Brown said:

Focus ring focuses. But it is not super precise with markings.
1. When setting the hyperfocal distance you position infinity to one end of the marking and read out your closest focus on the other end. No repositioning.
2. ALWAYS treat your hiperfocal distance GENEROUSLY, if you want proper hyperfocal for f/11 adjust it as if it were for f/5.6 (or at *least* f/8) on the focus barrel (but keep the f-stop at f/11). Those markings are approximate due to short focus throw, infinity or marked close focus might not always be sharp if set as indicated.
 

thanks,

so I understand that the ring is for information purposes only, it doesn't activate or do anything.

thanks a lot for the advice to go down a few steps.

[wda]

On an M lens it sets the aperture, but there is no transfer of information to the camera or EXIF.

[Sandokan]

The aperture ring sets the aperture - and you can see this on an M-lens as metal blades come in from the edge and limit the light going through the lens. 

The focus ring moves the glass elements which in turn focuses different areas of the scene onto the film/sensor. 

[pop]

When you turn the focus ring on a typical Leica M lens from infinity to 0.7m, you can observe that the body of the lens moves a little bit forward and backwards.

Try this little experiment: choose a scene where nothing moves much, such as your living room or your garden, and where there are things at different distances from where you sit. Open the aperture of the lens to its widest setting (the lowest number; for a Summicron that would be 2). Now take a number of photographs, each showing the same part of your scene, and set the focus ring of your lens for each photograph to a different distance, such as 0.7m, 1m, 1.5m, 2m, 3m, 5m, 10m and infinity. Now look at those photographs carefully on the screen of your PC, magnifying the images where needed. Observe which parts of the scene appear sharp in each picture and which parts are blurred, and which parts are only a bit blurred and so on.

This is what is meant by 'focusing'. When you turn the focus ring to the position which says '2m', then everything which is exactly 2m in front of the camera will appear sharp in your picture. Things that are closer to the camera and things that are farther away will be blurred in the image.

Stopping down the aperture, from 2 to 11, for example, will make things look less blurred that are closer to the camera or more distant from the camera. Mind you, they will not become really sharp, but you will not notice so much that they are not sharp. That's how zone focusing works. You still focus your camera at a specific distance, but because of the stopped down aperture things look rather sharp from 2m to infinity, for example. However, this only works if you don't magnify your image too much. If you do that, you will notice immediately that not everything is as sharp as you thought.

[lct]

The focus ring communicates with the camera through the roller cam (pic) and activates focus magnification aka auto-zoom in LV mode.

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[Xavi]

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17 hours ago, pop said:

When you turn the focus ring on a typical Leica M lens from infinity to 0.7m, you can observe that the body of the lens moves a little bit forward and backwards.

Try this little experiment: choose a scene where nothing moves much, such as your living room or your garden, and where there are things at different distances from where you sit. Open the aperture of the lens to its widest setting (the lowest number; for a Summicron that would be 2). Now take a number of photographs, each showing the same part of your scene, and set the focus ring of your lens for each photograph to a different distance, such as 0.7m, 1m, 1.5m, 2m, 3m, 5m, 10m and infinity. Now look at those photographs carefully on the screen of your PC, magnifying the images where needed. Observe which parts of the scene appear sharp in each picture and which parts are blurred, and which parts are only a bit blurred and so on.

This is what is meant by 'focusing'. When you turn the focus ring to the position which says '2m', then everything which is exactly 2m in front of the camera will appear sharp in your picture. Things that are closer to the camera and things that are farther away will be blurred in the image.

Stopping down the aperture, from 2 to 11, for example, will make things look less blurred that are closer to the camera or more distant from the camera. Mind you, they will not become really sharp, but you will not notice so much that they are not sharp. That's how zone focusing works. You still focus your camera at a specific distance, but because of the stopped down aperture things look rather sharp from 2m to infinity, for example. However, this only works if you don't magnify your image too much. If you do that, you will notice immediately that not everything is as sharp as you thought.

I have done the tests and I see the difference.
What I have observed is that it loses some mm, that is to say I started at 35 mm and I have the feeling that the last photo must be something like 33 mm. Does that make any sense? The camera was fixed on a tripod.

[pop]

29 minutes ago, Xavi said:

What I have observed is that it loses some mm, that is to say I started at 35 mm and I have the feeling that the last photo must be something like 33 mm.

I'm afraid that I don't quite understand.  I think you could mean one of two things:

(1) The lens becomes shorter when you set the focus to infinity and it becomes longer when set to a closer distance.

This is quite normal. That's how lenses work. The lens must be closest to the sensor (or film or any other medium) to make a sharp picture of something that's very far away, such as the moon. Don't point it at the sun, though. The heat of the image of the sun may damage your camera or even your eyes. As a matter of fact, the focal length of a lens is measured when it's pointing at something very far away. Therefore, your lens starts with 35mm at infinity and becomes something like 2mm longer when fully extended.

(2) You could also mean that the lens sees a wider angle of the scene in front when set to focus to infinity. This is also normal and it's also how lenses work. The closer the lens to the sensor, the wider the angle it projects to the sensor. If the sensor becomes longer (by focussing on something nearby), the angle of its view will become narrower.

That's a bit like when you stand in front of a small window. When you're immediately at the window, you can see a very wide angle. However, when you're standing far away, perhaps at the other end of the room, you will see only a narrow slice of the environment of your home. Try it.

Anyway, I think you could much profit from learning about the basics of photography, for instance about what a lens really does. That would make it much easier to understand how to use your expensive camera so that it makes pictures to your liking. There are many books about that topic, but I don't know any spanish ones, unfortunately.

Perhaps some members here could help you selecting a book appropriate to the topic.

[Jean-Michel]

Xavi,

Maybe you should visit the Leica store in Barcelona, I think it is in the Casanovofoto store or such in Barcelona. They may well have some basic photography books that you may want to obtain and learn from. Much more effective than trolling the web for bits of information, some useful, most not.

[jaapv]

It indicates the zone of acceptable unsharpness for an A4 print from film. As the magnification gets more, the zone shrinks significantly, as it diminishes, it increases. Digital capture will decrease the zone by approx 1.5 stops. The contrast in the image and the amount of detail will be of influence too. They only place that the image will be sharp however, is in the plane of focus that you focused on. Everything else will be progressively unsharp. 

Start reading up on how photography works. It will increase your enjoyment. 

 

 

22 hours ago, Xavi said:

Is the focus ring informative or does it do something?

Let me explain better

If I set the focal length to F/11 with a 35mm, that means I have focus from 1.8 meters to infinity according to the hyperfocal tables

Do I need to change the focus ring to that position?
Or does it matter since it is only informative?

 

[Xavi]

Thank you all very much for the information.
 

The truth is that one thinks one knows something about photography, one has even dared to do some exhibitions and enter some competitions in which one has done quite well until a Leica M arrives, which is making me read and search on the Internet more than ever.

The truth is that there is little in Spanish. I will go to Casanovafoto to see if they have something that helps me understand more about how a manual camera works both mechanically and in the photographic part and thus relearn photography again.

[jaapv]

That is really wise. May I suggest following an appropriate workshop, your camera dealer should be able to advise you. The first thing you will have to unlearn from your background: The camera does not take the image, the photographer does. The camera is just a tool to be controlled. 

[Kiwimac]

On 8/16/2024 at 6:15 AM, Xavi said:

Thank you all very much for the information.
 

The truth is that one thinks one knows something about photography, one has even dared to do some exhibitions and enter some competitions in which one has done quite well until a Leica M arrives, which is making me read and search on the Internet more than ever.

The truth is that there is little in Spanish. I will go to Casanovafoto to see if they have something that helps me understand more about how a manual camera works both mechanically and in the photographic part and thus relearn photography again.

It may depend on your age!

 

 When I began serious photography back in the very early 1980’s, all lenses worked this way because autofocus etc was non existent. 
 

For example, my first real camera was a Canon AE-1 Program that came with a manual 50mm lens (for some long-forgotten reason, cameras were usually sold with 50mm lenses as standard in those far off days) and that lens was marked, and behaved, exactly like an M lens today. 
 

It would have been a good decade after that (at least) before I owned a camera with autofocus. 
 

I’ve noticed that often (but not exclusively) confusion with using M cameras and lenses is more common in younger users who only ever knew AF and computer-enhanced camera systems with all manner of bells and whistles.