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
1,109
346
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
4,961
1,315
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
729
867
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
1,314
427
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
1,109
346
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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tiggy@mac.com

R5
CR Pro
Jan 20, 2014
711
605
Thetford, VT
www.camnostic.com
I find this unfocus-when-sleeping bug maddening. I hope it is not a matter that cannot be fixed in firmware due to a "parking" function of the focus mechanism. It alone would cause me to skip the RF 600 f/4 in favor of the EF Mark II version I already have.
 
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koenkooi

EOS 5D Mark IV
CR Pro
Feb 25, 2015
1,807
1,727
I find this unfocus-when-sleeping bug maddening. I hope it is not a matter that cannot be fixed in firmware due to a "parking" function of the focus mechanism. It alone would cause me to skip the RF 600 f/4 in favor of the EF Mark II version I already have.
Even if it parks, it is easy enough to store the position when going into sleep mode and restore it on wake-up.
 

tron

EOS R5
CR Pro
Nov 8, 2011
4,961
1,315
So for astrophotography (or timelapses in general?) an EF lens with the adaptor seems the most safe solution for now!

Unless maybe time to sleep set to never in combination with a power bank at around 45W with PD can save the day (or night!)
 

JPAZ

If only I knew what I was doing.....
CR Pro
Sep 8, 2012
1,109
346
So for astrophotography (or timelapses in general?) an EF lens with the adaptor seems the most safe solution for now!

Unless maybe time to sleep set to never in combination with a power bank at around 45W with PD can save the day (or night!)
Still “pondering” this. Obviously, never letting the camera sleep prevents the issue but then battery life enters the dilemma. I guess this issue applies to all the “focus by wire” lenses but it really only matters during nighttime exposures. I could use my Sigma EF 15mm “fisheye” and place gaffer tape on the focus ring once the focus is set but the RF lens is so much better for the night skies
 

LarsCS

Angry German
Jul 7, 2017
19
0
Colorado Springs
larsleber.net
There is an option in the menu. Something like “retract lens during power off” which is set to on as default. Turn it off. It messes up the focus even when a lens is set to manual focus when camera powers off/during battery changes. Took me a while to find it. Very annoying.