Silt interfering with camera focusing?

[darrenlowjq]

My camera failed on a few occasions this trip to focus on subjects that I was trying to shoot and the focal point was between my camera and the subject. I'm thinking that the silt in the water between my camera and the subject is wrecking havoc with the auto focus, does that sound right? Anything I can do to counteract that other than to not dive with people who kick up silt?

 

[Nemrod]

Switch from evaluative focus to center weighted or even spot focus. If you have the face recognition on then turn that to off.

Sometimes a camera may need a focus assist light if the light intensity or contrast is low.

I pine for a simple digital camera with a simple Manual focus and a simple Manual exposure mode and an Auto Aperture Priority mode and nothing else. I swear I could focus and shoot my Nikonos or any film SLR that I have owned faster than the autofocus on many cameras and more accurately as I knew what I wanted in focus.

Can you go to a Manual focus mode and zone focus?

N

 

[AngloFish]

Had this very issue when I first got my GH2. The only thing that ultimately solved the problem was introducing a set of nice lights, but I imagine a single focus light would be fine.

 

[JohnnyC]

Switch from evaluative focus to center weighted or even spot focus. If you have the face recognition on then turn that to off.

Sometimes a camera may need a focus assist light if the light intensity or contrast is low.

I pine for a simple digital camera with a simple Manual focus and a simple Manual exposure mode and an Auto Aperture Priority mode and nothing else. I swear I could focus and shoot my Nikonos or any film SLR that I have owned faster than the autofocus on many cameras and more accurately as I knew what I wanted in focus.

Can you go to a Manual focus mode and zone focus?

N

Even better is the Nikonos RS. The autofocus on that is amazing, and more accurate than I am. My 5D3 is noticeably slower.

 

[darrenlowjq]

@Nemrod: I need to go delve deeper into my camera manual to find out if what you are suggesting is possible, I suspect I am not using my camera to its full potential since I only recently moved from auto to aperture priority. Shooting a Sony RX100 just for your reference.

@Angiofish: Not sure more lights is going to do the trick. I'm already sporting a pair of Inon Z240s.

 

[AngloFish]

Wasn't sure if you had any or not, it completely cleared the issue up for me. I just went and checked, I'm using spot metering setting for auto focus if that helps at all

@Nemrod: I need to go delve deeper into my camera manual to find out if what you are suggesting is possible, I suspect I am not using my camera to its full potential since I only recently moved from auto to aperture priority. Shooting a Sony RX100 just for your reference.

@Angiofish: Not sure more lights is going to do the trick. I'm already sporting a pair of Inon Z240s.

 

[KeithG]

poor autofocus is generally caused by 2 things (that can be mixed together to make things morre confusing for you)
- silt (wrong subject)
- insufficient light (no autofocus)

silt provides a false target that your camera can successfully focus on instead of the real subject you wanted. you have a focus, just the wrong one.

insufficent light (ambient or artifical) will cause the camera to fail to acquire a focus. you do not have a focus and the focal point may be any random distance.

which condition are you trying to solve?

i have a camera that will not open the shutter in the second situation (no focus). what does your camera do?

 

[darrenlowjq]

I'll need to get back to you on that. I'm thinking the problem is the silt because I tried shooting with the exact same settings but where there was no silt in front of the subject and it focused correctly.

In any case, the point is kinda moot for now because clumsy me managed to flood my RX100 on the first dive today, so I didn't get the chance to fiddle around with the settings

 

[KeithG]

Not to rub it in...

Flooding a camera sucks BIG time. Key issue is to clearly identify "WHY?" so that you never repeat this adventure. Most common cause is user error. I have been "diligent" and have never had a flood since my very first video camera flooded due to a manufacturer defect (video housing port not seated properly).

On a recent trip one of the photogs with a high end rig claimed a flood failure of some type EVERY trip. This was echoed by another diver who carried 2 duplicate rigs ($10k each!) WTF? The first diver had both a strobe and internal flash failure on that trip.

Both divers appeared to consider a flood every trip as "normal". I was appalled at their cavalier attitude. More money than brains.

I now consider a flood as a simple personal mistake.

So the first questions are:
- what happened?
- what did I do wrong?
- how can I prevent this?

P.S. I carry a backup camera and housing on every dive trip, but this plan only covers me until day #2...

 

[Nemrod]

Both divers appeared to consider a flood every trip as "normal". I was appalled at their cavalier attitude.

While mechanical issues can occur I suspect their flood every trip a result of their "cavalier attitude."

N