Focus

[nadwidny]

I'm having a problem getting consistent focus when shooting. Sometimes everything is nice but a lot of the time things are not in focus. What I'm doing now is autofocusing on the surface at an object 3 or 4 feet away. Set to manual and then infinity. Zoom is set to full wide. Is this there any difference in doing this above or below the water?

Equipment is Sony PD150 in a Gates housing with the WP35 port.

Thanks in advance for any help!

 

[Marinevisions]

Have you tried using manual focus in the water, without trying to set focus on the surface?

 

[nadwidny]

Yes. Quite often I'll find that I need to reset my focus in-water and I find that the focus in these instances is usually less than optimal. Since I dive mostly in dark waters without a ton of contrast is it possible that I need more contrast when setting focus in-water? I try and find an area with the most contrast but usually I'm looking at brown on green or brown on brown areas. I'm thinking of duct-taping a white cross on my black fins and see if that helps.

I guess my biggest question is if I 'm going to do the "autofocus/switch to manual then go to infinity" what distance should I be focusing at? 3-4'? Further? Should there be any zooming in or out going on while I'm doing this

Also is there be a depth of field factor to consider if I do my preliminary focus in bright light then shoot in dark?

 

[nadwidny]

Just to follow up this problem-

I found this week that the issue is with setting the camera to infinity. When I would "auto focus on a subject-set to manual-set to infinity" as I had been coached, that things would mess up.

So what I did is auto-focus on something around 3-5' away at the beginning of the dive and not add the infinty setting and use that for most of the rest of the dive. This worked out very well. I checked this out while patching the camera to a TV. I would auto-focus on objects at varying distance within the boat, hit manual (things were fine), then hit infinity (everyting went out of focus).

I'm not sure if this is a specific problem with my camera or if this is just the way it goes. I'm just happy I figured it out.

 

[Annie Crawley]

Brian,

Auto focus versus manual focus versus infinity in different situations leads to different solutions.

From what it sounds like, you are in extremely dark, murky waters so that you will have a lot of grain in your images...is your gain on? This will lead some focus to look out of focus because of the high grain. Are you using lights? I did not hear you mention lights. The auto focus to manual to infinity does not work often. If you check your manual I believe to get infinity focus you set zoom as wide as it can go and then objects that are about three feet away and further will be in focus. The grain and aperture setting will affect your depth of field. If you use auto focus and then change to manual, you may not be able to change the focal length at all and need to shoot only the distance from the objects you have set it in. In low light situations, it is much more difficult to focus than with light and clearer water. The auto focus may even be out of focus and unable to lock focus...but that technique, auto to manual is your best bet underwater.

Hope this helps...

 

[nadwidny]

Annie,

Most of my filming is done in dark, bad viz water. I use lights all the time. My camera is set to "Auto Lock" so I'm not sure if the "Gain" setting is an issue.

To help discover that setting my camera to infinity was the problem I did it on the surface while the camera was hooked up to to monitor so I could instantly see what effect going to each setting would produce. I would shoot different subjects at varying distances by using "Auto" going to "Manual" then going to "Infinity". The results were always the same, good focus at "Auto", still good when I switched to "Manual" then everything would go slightly in the crapper when I sent to "Infinity". It didn't matter whether I was focusing from 2' to 2 miles, the results were always the same. At "Infinity" things went off.

2 weeks ago I was on a liveaboard trip in Northern BC and on my first dive I did my usual "Auto" to "Manual' to "Infinity". The footage for that dive was as usual, slight out of focus. After that I only shot "Auto" to "Manual" and never set "Infinity". Footage was clear and in focus. Yay!

I'm thinking that this is a problem peculiar to my camera (PD150). I'm just glad that I got it sorted out so that it works as it was very frustrating. However I will also check out the gain and see if there is something going on with that.

Thanks for the reply. I look forward to attending one of your workshops in the future and got a lot out of your DVD.

 

[Annie Crawley]

Brian,

Thought your name sounded familiar...

I know this might sound funny...but check the user manual. My first video camera I owned kept giving me problems with white balance and focus. For more than a year I struggled and then I had an error message that I had to go to the manual for...and it solved all my other problems.

After you do that and see that it is not operator error, then I would get your camera checked out because what you are describing is happening should not be happening...

Would love to have you on one of the trips. We still have three spots for Southern Islands and Five for Northern in September!

Talk with you soon,

Annie