Manual focus and infinity

[Merlin5]

Hi guys. I'm just messing around in my kitchen with my Sony a6600 on the tripod pointing at the window to my garden. I've never done manual focusing so am teaching myself, and I'm focusing at infinity using my 16mm lens. I wonder if you can tell me if I'm doing this right. I've got the peaking setting display enabled, level on mid and colour on blue. I've set the aperture to f16, iso 100, and 1.3 seconds shutter speed is giving me correct exposure. In order to manually focus I thought I could just turn the focus ring on the lens and see it change from blurred to sharp. It seems that when I press the AF/MF button on the back of a6600 it zooms right in to whatever my focus box is looking at and a horizontal slider appears on screen showing distances starting at 0.2m at the far left to the infinity symbol which appears just past the halfway mark. Should I set infinity right at the point it first appears on the slider from the previous metre distance or slide it to the very end? I did a couple of test shots, one at infinity and one a few metres less than infinity and didn't really see much difference? Although my garden doesn't disappear into the distance so probably not a great test and maybe I'd notice it more with a proper scene in front of me.

Also, when would I need to use the other distance markings, would it be when I need to set focus at a specific hyperfocal distance, say with something like that photo pills app when it tells you what distance to set? So in a nutshell, setting focus to infinity or any specific distance can only be done manually like this and not using auto focus, is that correct?

 

[LeeRatters]

At f/16 you aren't going to notice much difference anyway with such a big depth of field especially at 16mm

 

[ancient_mariner]

As Lee said, at f16 on a 16mm lens you aren't going to see much difference - in fact everything from a few feet away to infinity will be more-or-less in focus with that focal length and aperture.

*Personally* I find focus peaking unreliable for critical focus when using a telephoto lens and wide aperture i.e. 135mm and f2.8 or 85mm and f1.4. Using the setup you described, I would suggest turning off peaking and using the following 2 approaches:
1) Set the lens at its widest aperture, then use the magnification of the viewfinder to focus on the part of the image you wish to be in focus. When that is sharp, set the required aperture, compose your shot and take the picture
2) Learn about hyperfocal distance, then using the scale in the viewfinder when magnified set the focal distance to give you the depth of field you require in combination with the aperture. Compose & take the shot.

Note that the distance scale will only show up using a true FE mount lens - if you use a manual adapted lens then the camera has no idea what's going on, and even if you magnify the screen it won't know the distance you've focussed to.

 

[Merlin5]

Thanks Lee and Toni.
Toni, A couple of points you made that I'm not clear on so hope you don't mind me being a bit slow, lol.
What is the benefit of focusing at the widest aperture, in my case f1.4, rather than focusing straightaway at the aperture I'm going to use?
About the distance scale showing up, I take it my Sigma is a true FE mount lens as I see the distance scale when I magnify?

 

[ancient_mariner]

What is the benefit of focusing at the widest aperture, in my case f1.4, rather than focusing straightaway at the aperture I'm going to use?

As you stop down the depth of field of focus increases - as you discovered in this situation, it can prevent you knowing what point in the image you are actually focussed on. Opening to maximum aperture will give a relatively shallow depth of field and will allow you to see where you have focussed. You could, of course, use the distance scale to guess where you've focussed, just like we used to with older cameras without a system to just what will be in focus.

About the distance scale showing up, I take it my Sigma is a true FE mount lens as I see the distance scale when I magnify?

Correct. A non true FE mount lens would either require an adapter (like my Nikon manual focus lenses) or have a mechanical mount without electronic connections (like some of the manual focus Samyang, Meike etc lenses).

 

[Merlin5]

As you stop down the depth of field of focus increases - as you discovered in this situation, it can prevent you knowing what point in the image you are actually focussed on. Opening to maximum aperture will give a relatively shallow depth of field and will allow you to see where you have focussed. You could, of course, use the distance scale to guess where you've focussed, just like we used to with older cameras without a system to just what will be in focus.



Correct. A non true FE mount lens would either require an adapter (like my Nikon manual focus lenses) or have a mechanical mount without electronic connections (like some of the manual focus Samyang, Meike etc lenses).

Thanks Toni, understood. I really appreciate the free photography lessons I get on these forums from experienced members such as yourself.

 

[Nod]

IF your lens has focus distances marked on it, you could see where "infinity" really is by using a combination of A and MF with one of the distant planets as a target - the Moon will do if the planets are too small for a 16mm to find.
Personally, I'd try to avoid f/16 to stay clear of diffraction softness. f/11 should give enough DoF.

 

[Merlin5]

IF your lens has focus distances marked on it, you could see where "infinity" really is by using a combination of A and MF with one of the distant planets as a target - the Moon will do if the planets are too small for a 16mm to find.
Personally, I'd try to avoid f/16 to stay clear of diffraction softness. f/11 should give enough DoF.

I'll try that. So if I'm manual focusing on the moon and it's sharp before I reach the infinity symbol, then that is infinity?

 

[ancient_mariner]

I'll try that. So if I'm manual focusing on the moon and it's sharp before I reach the infinity symbol, then that is infinity?

That's only true for a fully mechanical lens - it won't work for an electronically focused lens.

 

[Nod]

I'll try that. So if I'm manual focusing on the moon and it's sharp before I reach the infinity symbol, then that is infinity?

TBH, it'll probably be close to the infinity symbol (or, at least, it SHOULD be!) At worst, it'll give you a good idea where infinity is when you're hyperfocussing. (Personally, I usually choose a specific object as the focal point and use f/8 or f/11 if I need to get enough DoF for the rest of the scene, especially when using a UWA.)