Always learning - A tale of the RF 15-35 and a dark night

JPAZ

If only I knew what I was doing.....
CR Pro
Sep 8, 2012
1,073
208
All,

Tried to do some Milky Way shots over the weekend. Set up the composition with a foreground tree and was in an appropriately dark place. The sky, unfortunately did not cooperate due to some wildfire induced haze, and the images are just so-so. But, I had some new experiences with the RF 15-35 f/2.8 on my R5.

After calculating the hyperfocal distance and placing myself the correct distance from the tree, my practice shots had the tree and the sky all the way to the horizon in reasonable focus. Then, I awaited the sunset. But, when I took my first shot, the focus was way off. I had to shine a bright light on the tree, refocus, then proceed with a few shots. After waiting 15 minutes of so for the next set of exposures, the same thing occurred. I'd use manual focus with the light (isn't the R5 manual focus great, by the way?), get things set, and take a series of images that would be in focus, again. The cycle repeated. In frustration, once the focus was set, I placed a piece of gaffer tape to keep the ring from moving, but after the next 15 to 20 minute interval, the focus was off again.

Then, it occurred to me. This lens uses "focus by wire". When the camera went to sleep, I am betting the focus reverted to its baseline state. I increased the "go to sleep" interval to 10 minutes (I usually keep it at one minute to conserve the battery), and it helped.

Is my assumption correct or is there a problem with the lens? If this behavior is normal, then lets all learn from it. Another difference between my DSLR with EF lens setup.................

Appreciate any comments in advance.

JPAZ
 
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tron

EOS R5
CR Pro
Nov 8, 2011
4,891
1,204
I have the set but haven't tested it for this. What you say is useful to know (I believe that your assumptions are right).
 

navastronia

EOS RP + 5D Classic
Aug 31, 2018
713
845
Yep, this is the reason I use manual focus lenses for my video work, where often the camera will go to sleep between takes, and maintaining the same focus point from take to take is critical. I'm sorry you had this frustrating experience!
 

Antono Refa

EOS R
Mar 26, 2014
1,291
424
The R5 will use the focus by wire to change the lens' focus to some baseline when it goes to sleep, but doesn't set it back to whatever it was before it went to sleep, much the less have an option to use the focal length & aperture to set the lens to hyperfocal distance on its own?

Ah, the wonders of modern technology!

[Spare me the 'a photographer should be able set the lens to hyperfocal distance on his own'. My point is, if new technology doesn't save one work, it should at least not break anything.]
 
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JPAZ

If only I knew what I was doing.....
CR Pro
Sep 8, 2012
1,073
208
BTW, less annoying but if we are talking about a firmware fix, the B (Bulb) timer reset with each "go to sleep" as well. I was using 7 seconds but after waiting a bit, the timer reset to a "disabled" as well. And that's not a lens issue at all.
 
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