Disturbing Discovery Regarding Sharp Focus.
Feb 28, 2019 20:22:49 #
Today I went out to shoot Snowy Owls. While being parked, waiting for them to leave the field and fly in my general direction, I noticed something disturbing.
With my Nikon D5 and the 300mm PF, f/4 lens, I focused on a stationary branch in preparation and speculation that the Snowy would land on it. While using back button focus, the branch was initially sharp and then slightly out-of-focus and then back to sharp. It continued to repeat the same process.
I was wondering if anyone has an explanation as to why and if there is a way to stay focused and sharp. I should mention that my engine was running while I shot out the window.
Harold
With my Nikon D5 and the 300mm PF, f/4 lens, I focused on a stationary branch in preparation and speculation that the Snowy would land on it. While using back button focus, the branch was initially sharp and then slightly out-of-focus and then back to sharp. It continued to repeat the same process.
I was wondering if anyone has an explanation as to why and if there is a way to stay focused and sharp. I should mention that my engine was running while I shot out the window.
Harold
Feb 28, 2019 20:43:07 #
Even if it wasn't the issue in this case, from personal experience I know that exhaust can interfere with clarity - just like heavy haze or fog. So maybe focus too?
Shooting across a hot pavement from which heat is rising is similar.
Shooting across a hot pavement from which heat is rising is similar.
Feb 28, 2019 20:44:51 #
Feiertag wrote:
Today I went out to shoot Snowy Owls. While being... (show quote)
Were you constantly holding the bbf in? If so it was probably focusing on the branch then possibly on the background... or you are just refocusing as long as you hold it in. Pressing bbf to focus, then leave it unpressed should retain the focus setting
Feb 28, 2019 20:46:07 #
Feiertag wrote:
Today I went out to shoot Snowy Owls. While being... (show quote)
Herold, I had the same problem today except it was with a Canon 6D Mark II and my Tamron 150-600mm G2 lens while sitting in the car with the engine running. I belive mine was due to camera shake it would try to refocus when the point left the Blue Herions head and wanted to focus on what was behind it.
Feb 28, 2019 20:50:09 #
In my mind are are two possible culprits, neither camera related
1. camera motion caused by motor vibration
2. heat waves, either from the car's radiator or exhaust.
Another (camera related) cause may be that you were using spot focus and the spot was drifting off the target branch occasionally due to your hand holding the camera /lens.
1. camera motion caused by motor vibration
2. heat waves, either from the car's radiator or exhaust.
Another (camera related) cause may be that you were using spot focus and the spot was drifting off the target branch occasionally due to your hand holding the camera /lens.
Feb 28, 2019 20:54:18 #
Feiertag wrote:
Today I went out to shoot Snowy Owls. While being... (show quote)
The main reason why I use a carpod and facial stabilizer .....
..
Feb 28, 2019 23:30:11 #
IS/VR trying to compensate for movement by you or the vibration from the running engine.
Mar 1, 2019 05:48:05 #
As you press and release the focus button vibration reduction will turn on and off. This may be what you are experiencing rather than a shift in focus.
Mar 1, 2019 05:54:53 #
Getting a clear shot from a warm car in the cooler weather can be problematic. Heat from the cabin creates heat waves as it escapes into the outside world.
Mar 1, 2019 06:33:15 #
billnikon
Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont
Feiertag wrote:
Today I went out to shoot Snowy Owls. While being... (show quote)
IF the branch moved at all in a slight breeze, it is hard for a camera to hold on a single branch, too many other branches around for a sensor to ignore. I find the same on all my camera's, even in single spot.
You could go manual after focus is established.
Mar 1, 2019 06:41:02 #
billnikon wrote:
IF the branch moved at all in a slight breeze, it is hard for a camera to hold on a single branch, too many other branches around for a sensor to ignore. I find the same on all my camera's, even in single spot.
You could go manual after focus is established.
You could go manual after focus is established.
This sounds like the most plausible reason why it was in and out of focus. I thought perhaps camera movement was the reason, but I like that the subject could be moving as a better solution.
Mar 1, 2019 06:49:33 #
If the air outside was colder than the air inside the car, you were getting heat distortion. People often dismiss it because they don't fully understand it, but I'll bet you a lunch that's what it was. A rolled down window with a temperature differential between the inside and outside is 100% guaranteed to cause heat distortion / diffraction and it will interfere with the AF system. You must have the car at the same temp as the outside air. (And you should shut the engine off too to reduce vibrations). This should help:
https://backcountrygallery.com/long-lens-heat-distortion/
https://backcountrygallery.com/long-lens-heat-distortion/
Mar 1, 2019 07:44:11 #
Steve Perry wrote:
If the air outside was colder than the air inside ... (show quote)
Thanks for sharing Steve!
Mar 1, 2019 07:44:58 #
Thank you for all the informative posts.
I am guilty as to what Steve has described as, heat distortion. It was extremely cold outside and warm in my vehicle. If you haven't seen his video, I suggest you do.
https://backcountrygallery.com/long-lens-heat-distortion/
Harold
I am guilty as to what Steve has described as, heat distortion. It was extremely cold outside and warm in my vehicle. If you haven't seen his video, I suggest you do.
https://backcountrygallery.com/long-lens-heat-distortion/
Harold
Mar 1, 2019 07:52:11 #
Were you using single point focus? When auto focus is iffy, I use manual.
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