# Anyway to lock to focus of an RF lens / Body?



## wockawocka (Jan 28, 2022)

Sup guys,

I have a problem that maybe you can help with. I shoot weddings and when I do the dancefloor I run a combo of the 35 1.4 mkii and the EF 16-35 F4 IS.

This question is about the 16-35 and it's bigger brother the RF 15-35 2.8

When I shoot a dancefloor I use strobes on camera and behind the subject and the lens is set to manual focus, infinity and the camera is set to F8. Essentially the old pj rule of 'F8 and be there'

I'd like to move to the RF 2.8 version as it's not that much heavier than the combined weight of the F4 + adapter and I'll benefit from better EVF performance when it's super dark.

Yet, because it's in manual focus I worry I'll knock the ring somehow and throw the focus without realising it. I get around this with the EF version by putting a rubber band around the focus ring but I'm wondering if there's a more elegant way to fix the focal point via the body. I've never really liked using the rubber band because I get comments of 'Did you break your lennnnns'? and it seems a clunky (albeit effective) solution.


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## old-pr-pix (Jan 28, 2022)

As one of those old pj guys I've relied on the 'f8 and be there' rule extensively - actually my old Graflex 510 volt flash had enough power to make that f11 often. The whole point was to capture a usable shot in situations where you didn't have time to focus correctly. 

I think you may be over constraining yourself by keeping focus locked at infinity. Consult one of the on-line hyperfocal or DOF charts - using f8 your ideal focus point should be short of infinity. At 16mm and f8 most every distance should be in acceptable focus if the lens is set at its hyperfocal distance. Even at 35mm a focus at ~ 8-10 ft. should cover most everything on a typical size dance floor. Personally for dance floor shots I often liked to use a little slower shutter even with strobes. That picks up more ambient light so backgrounds aren't so black and leaves a very slight touch of motion blur just to give a sense of action/energy. With that, critical focus is even less important. Obviously that may not be to your liking or fit your style.


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## gmaxwell (Jan 29, 2022)

I have no experience to contribute, but you might consider getting a cine follow focus with a locking knob on it (and add a gear ring to the lens). You could mark off on it the hyperfocal distances for varrious stops and focal lengths. On the fly-by-wire lenses it might be a little irritating to get the offset right, since I think the offset between the ring and the actual focus distance changes any time you go in and out of AF mode.

This is a case where the fact that the camera firmware isn't open source really hurts. It would be pretty simple for the camera to have an "automatic hyperfocal focus mode", where you set the camera in M or Av and it automatically focuses to the relevant hyperfocal distance for the current focal length and aperture-- or just a focus lock where you set it to infinity and it stays there. It would be an obscure enough feature that it's not worth the camera makers time to add it because it wouldn't sell any more cameras (and doesn't help sell fast lenses... maybe it would sell expensive strobes) but I can imagine a lot of situations where I might use it if available.


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## kaihp (Jan 29, 2022)

old-pr-pix said:


> As one of those old pj guys I've relied on the 'f8 and be there' rule extensively - actually my old Graflex 510 volt flash had enough power to make that f11 often. The whole point was to capture a usable shot in situations where you didn't have time to focus correctly.
> 
> I think you may be over constraining yourself by keeping focus locked at infinity. Consult one of the on-line hyperfocal or DOF charts - using f8 your ideal focus point should be short of infinity. At 16mm and f8 most every distance should be in acceptable focus if the lens is set at its hyperfocal distance. Even at 35mm a focus at ~ 8-10 ft. should cover most everything on a typical size dance floor. Personally for dance floor shots I often liked to use a little slower shutter even with strobes. That picks up more ambient light so backgrounds aren't so black and leaves a very slight touch of motion blur just to give a sense of action/energy. With that, critical focus is even less important. Obviously that may not be to your liking or fit your style.


At 16mm f/8, the hyperfocal distance is 1.08m (0.7m- inf)
At 35mm, it's 5.14m (2.77m- inf)
For 35mm, the 2.77m might be trouble on a dancefloor, so I'd the distance to 4m, then you get in-focus to be 2.25 - 17.92m which is probably quite satisfactory for the shots.


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## SereneSpeed (Jan 29, 2022)

I have to ask... Is Auto Focus not up to the job? It takes a split second in the R3/5/6.

Maybe keep the EF 16-35 and change to an R6 instead?

I guess I just don't see the reason to lock AF. I shot a couple weddings with my EOS R and using OCF and AF never let me down, from 24mm f2.8 and even up to 85mm f1.4 (and deeper DOF as well).


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## wockawocka (Jan 30, 2022)

old-pr-pix said:


> As one of those old pj guys I've relied on the 'f8 and be there' rule extensively - actually my old Graflex 510 volt flash had enough power to make that f11 often. The whole point was to capture a usable shot in situations where you didn't have time to focus correctly.
> 
> I think you may be over constraining yourself by keeping focus locked at infinity. Consult one of the on-line hyperfocal or DOF charts - using f8 your ideal focus point should be short of infinity. At 16mm and f8 most every distance should be in acceptable focus if the lens is set at its hyperfocal distance. Even at 35mm a focus at ~ 8-10 ft. should cover most everything on a typical size dance floor. Personally for dance floor shots I often liked to use a little slower shutter even with strobes. That picks up more ambient light so backgrounds aren't so black and leaves a very slight touch of motion blur just to give a sense of action/energy. With that, critical focus is even less important. Obviously that may not be to your liking or fit your style.


My bad, I wasn't thinking straight , it's usually set to 1.5m!


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## wockawocka (Jan 30, 2022)

SereneSpeed said:


> I have to ask... Is Auto Focus not up to the job? It takes a split second in the R3/5/6.
> 
> Maybe keep the EF 16-35 and change to an R6 instead?
> 
> I guess I just don't see the reason to lock AF. I shot a couple weddings with my EOS R and using OCF and AF never let me down, from 24mm f2.8 and even up to 85mm f1.4 (and deeper DOF as well).


It isn't really. I mean, perfectly ok during the day but if someone is pouring tequila down the throat of another on the dancefloor I don't want to rely on the AF. Electric slides, The Worm, chair lifts.... it's not something I can risk missing as often these things are one chance deals.


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