Autofocus then switch to manual?

[r042wal]

I have an A7RII and am going to try a Milky Way shot but I'm unsure of how to set a feature.  I have to set the hyper-focal distance first which is 2.5m.  The guide I am following suggests using the camera's auto focus system to acquire proper focus and then set manual focusing so it won’t move.

 

I am gong to be taking a series of shots with a remote camera trigger so how do I get around holding the AEL button in?  Is it possible to switch to manual focus after letting auto focus acquire the proper focus?

 

Thanks in advance.

[Username]

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None of the above makes any sense.  

 

But I do know that various remotes differ in function. 

Maybe you should have one that activates AF, plus  

another that only triggers the shutter.

   

Hyperfocal ? 2.5M ? WTF ?  All astro subjects are 

at infinity. No, thaz not a joke. 

   

Nobody needs AF. It's just a convenience. So in any  

circumstances where AF proves inconvenient, kill it. 

If you don't know how, get a MF lens. 

[r042wal]

Thanks for the reply.  I am going for a shot of the Galactic Center, vertical, with landscape in the background.  I plan to stack about five images.  The article first tells me to auto-focus on a marker placed at the hyperfocal distance, then switch to manual focus and do not alter the focus from that point forward.  The idea is to get the greatest depth of field by focusing from the hyperfocal distance to infinity.

 

I just don't understand the concept of going from AF-S to manual focus.  If my subject is in focus when my camera is set at AF-S, will the subject stay in focus when I switch to manual focus?  My lens does not have a manual focus switch.

 

Thanks once again.

[cws]

I just don't understand the concept of going from AF-S to manual focus.

Probably so that it doesn't start hunting focus once you are shooting... you are basically locking everything down.

[r042wal]

And that is my question.  I guess the answer it to try it and find out

[bobbyroe]

r042wal,

 

If you want to focus on a set object (hyperlocal distance or otherwise), you can do it in a number of ways:

• Fully manual focusing
• AF-S (or any other AF setting)

If you want to use AF (any setting), focus on the object (at whatever distance you're wanting), and then release the shutter button. The focus will now stay there until you initiate focusing again (whether with AF or manual). So now that you've "set" focus at the distance you want, just turn off AF (use C3 or whatever other custom button you may have set), and then shoot as you wish. Focus will not change unless you've "told" the camera to do so, either by AF or manual movement of the focus ring.

 

Works for me… hope it does for you, too.

 

Happy shooting,

 

Bobby

[r042wal]

Problem solved.  The AF/MF centre button is set to 'hold' by default.  Since it is programmable, I set it to 'toggle' instead.  If I AF on a subject and press the AF/MF centre button, the focus locks, even if I press the shutter button down half way.

[Username]

.... for a shot of the Galactic Center, vertical, with landscape in the background.  

I plan to stack about five images.  The article first tells me to auto-focus on a

marker placed at the hyperfocal distance, then switch to manual focus and do

not alter the focus from that point forward.  The idea is to get the greatest depth

of field by focusing from the hyperfocal distance to infinity.

 

........

   

Sounds like wrong advice to me. Astro subjects are mostly point source 

or multiple point sources. Please consider that DoF is not really in focus. 

Only the actual plane of focus is in true focus. Point sources demand an 

accurate focus, and are not very suitable for the "almost focus" known

as DoF.

   

OTOH your nighttime landscape tends to silhouette, which DOES work 

out verrrrry well with the "almost focus" of DoF.  

  

IOW, forget hyper focal. Get dead accurate focus on your point sources 

and accept the whatever degree of "almost focus" is rendering all your 

silhouetted foliage, etc. Compomising your point source focus to slightly 

improve edge sharpness of silhouettes is absolutely toadally WRONG. 

  

If this advice comes from some "expert", in the future consider another 

expert, or at least greatly discount advice by your current "expert" :-)   

  

So. Do NOT autofocus. Use your live view MF magnifier, at maximum,  

to focus your point sources and lock/tape/glue/etc your lens to hold at 

that focus. Let the silhouettes render however they may render. They're 

far enuf from the camera to be at "approximate infinity" anywho. There 

is no justification there for using a "hyperfocal" focus setting. 

[Colorado]

" I am going for a shot of the Galactic Center, vertical, with landscape in the background" 

 

Just want to know where you shoot making the "landscape" the back ground as compared to the

"Galactic Center"? LOL.

[r042wal]

[Guy R]

Well worth the effort Adam. That is a great shot.

Did you light the foreground in any way?