Focus with Canon 5d Mark ii

Hello all,

I was just watching some of the footage I shot on a recent dive trip, and about 20% of my shots were out of focus. Some worse than others. I use a canon 5d mark ii, and have been using it on the multi point focus. Typically, I will just use the auto focus (pressing the AF button down, while pointing at a coral head). I can't do manual focus, as I have an ikelite housing.

I got to thinking today, maybe I should be doing center focus only. What does everyone else think? Am I doing this wrong?

Any thoughts on this would be appreciated.

Dustin

Hello all,

 

I was just watching some of the footage I shot on a recent dive trip, and about 20% of my shots were out of focus. Some worse than others. I use a canon 5d mark ii, and have been using it on the multi point focus. Typically, I will just use the auto focus (pressing the AF button down, while pointing at a coral head). I can't do manual focus, as I have an ikelite housing.

 

I got to thinking today, maybe I should be doing center focus only. What does everyone else think? Am I doing this wrong?

 

Any thoughts on this would be appreciated.

 

Dustin

Hi Dustin

Centre focus makes no difference. Auto focus does not work with 5D MII in video mode. You need to pre-focus in camera mode and then switch over. Not good for moving subjects. Lens choice is important too. So focus manually but you will need to have a custom focus mechanism on the Ikelite port - not easy to do as their port usually have very little room.

In video mode (live view) the 5DMII has no auto focus. If you shoot with a wide angle lens then the best is to achieve closest focus distance to infinity (hyperfocal) and just keep that distance and take panning shots. I shoot with a 5D MII in a Zillion housing with custom MRS magnetic ring port by Inon for macro and close up shots. It was hard work and difficult to get smooth continuous manual focus. A tiny bit out and the video is not sharp.

Hope this helps.

Regards

David

I'm not sure what you are asking. Are you trying to prefocus before going into Live View or use the Quick Focus?

What I do is use Quick Focus mode in Live View to focus on a point then shoot then refocus on another subject then shoot. This usually works better with wide angle lenses which also give better DOF. For a 16mm, I just focus on a subject about 4 ft away @ f8 or so and let DOF take care of the rest for big subjects.

What David is saying is there is no AF while recording. If you want to change focus distance, you have to stop recording, refocus, then roll again.

Thanks for your relies David and Drew. I am sorry, I wasn't very clear. Let me try to rephrase, as I think my terminology and general explanation was a bit confusing.

I understand the camera doesn't have Auto Focus while shooting. I was referring to focusing before the shot.

I also use Quick Mode in Live View, I try to focus on the reef, a few feet away, before I hit the record button. I do this by hitting the 'AF-ON' button, until it focuses, then hit the record button.

The 5d mark ii has 9 focus points on the screen. Which currently I have the camera set for multi point focusing. Typically, it will light up several of these focus points, when I hit the AF-ON button.

Also, on the camera it allows you to choose your focus points. By hitting the 'AF Point Selection/Magnify' button on the upper right hand side of the back of the camera. It can be set to have all focus points available to focus or just one of them. Letting you choose which one, you want. My question is. Do others have all 9 enabled for video, or just the center focus point enabled?

The reason I ask this question, is I was poking around other non underwater websites, and people claim that the outer focus points are not good, and to do a center focus point only. I was wondering if the reason some of my footage was out of focus, was because I had all 9 points enabled. As the camera would use multiple focus points, instead of just the center.

My understanding is that the outer focus points are not as fast/good at grabbing focus, and the central point is more sensitive. I think if you are successfully getting a focus lock, all of the points that light up have found focus. If the outer points have found focus, how can that focus be inferior to focus found another way? It just might be slightly slower, especially in low light.

Be careful of your Aperture settings too. With a sensor that large anything more open then F5.6 (maybe even F8) and you are going to start getting a shallow DoF. This is not so bad with open water backgrounds but if you have something like a busy reef or a shoal of fish in the background then large parts of the shot are going to be out of focus. Ironically what is a massive benefit of HDSLR's above water is definitely their bane when shooting video underwater.

Cheers, Simon

Hi, I'm only starting to understand my 5D mk2 and have still not got a housing (infact this is my first post and will be asking a lens question very soon!). However I borrowed an Ikelite housing from a professional photographer friend who was looking over my camera. He suggested I change the focussing points from multiple to central... it so happens I was having focussing problems with stills and a 50mm lens (I only use manual focus topside with video). I am not technical, so cannot relay his technical explanation here, but can only liken the focusing points to dynamic range, in that the multiple focusing points create shallower more compromised angles between the points, whereas the single one is the strongest. I took the camera and the housing in for a test dive on Christmas eve in a dark Scottish loch, my old L&M HID lights with a Sigma 14mm and got clear in focus video and stills using the AF-on button for focus before shooting...if that camera can handle a newbie user with an unfamiliar housing, old lights and dark lochs then I would suggest use the central focus selection!

Sorry should also add that the AF-on focus button uses contrast to focus? Just a thought at why using multiple points specifically for U/W might not be a good idea (I'm asking myself this too!) Thanks

Be careful of your Aperture settings too. With a sensor that large anything more open then F5.6 (maybe even F8) and you are going to start getting a shallow DoF. This is not so bad with open water backgrounds but if you have something like a busy reef or a shoal of fish in the background then large parts of the shot are going to be out of focus. Ironically what is a massive benefit of HDSLR's above water is definitely their bane when shooting video underwater.

 

Cheers, Simon

Thanks Simon for the response. I don't think it is the aperture in my case. I was using mainly f11 and f8. I know you use the 7d mostly, but also have read that you have used the 5d before. Did you use center focus, or multi point focusing when using the 5d?

Hi, I'm only starting to understand my 5D mk2 and have still not got a housing (infact this is my first post and will be asking a lens question very soon!). However I borrowed an Ikelite housing from a professional photographer friend who was looking over my camera. He suggested I change the focussing points from multiple to central... it so happens I was having focussing problems with stills and a 50mm lens (I only use manual focus topside with video). I am not technical, so cannot relay his technical explanation here, but can only liken the focusing points to dynamic range, in that the multiple focusing points create shallower more compromised angles between the points, whereas the single one is the strongest. I took the camera and the housing in for a test dive on Christmas eve in a dark Scottish loch, my old L&M HID lights with a Sigma 14mm and got clear in focus video and stills using the AF-on button for focus before shooting...if that camera can handle a newbie user with an unfamiliar housing, old lights and dark lochs then I would suggest use the central focus selection!

 

Sorry should also add that the AF-on focus button uses contrast to focus? Just a thought at why using multiple points specifically for U/W might not be a good idea (I'm asking myself this too!) Thanks

Thanks for the response. And welcome to Wetpixel! That is good info, I will have to try the center focus on a future trip. What brought up my original post was that I was just curious what others do that have more experience than I have with the 5d mark ii video.

When using the AF I've never tried the center focus technique so it looks like I've got something else to try out now!!

For WA I mainly try to set the camera focus to infinity or whatever that becomes through the dome (ie hyperfocal like David describes above). This technique is widely used on all video cameras not just HDSLR's and almost always seems to give the most consistent results underwater. The only issues I have with this technique on HDSLR's is that occasionally I've had the focus barrel move on the lens and with no direct control through the housing I've then spent the rest of the dive cursing all things Canon!

Cheers, Simon

This takes us back to the days of the Nikonos 15mm lens. We used to set it at f8 and hyper focal distance.

These days, with wa lenses, I lock focus on my fin. So everything is in focus from 2 feet to infinity, as long as the f stop is f8 or smaller.

Be careful of your Aperture settings too. With a sensor that large anything more open then F5.6 (maybe even F8) and you are going to start getting a shallow DoF.

From experience Simon if you are in reasonably clear water say 15m vis, at a depth of 15m with your 7D at lets say 640 ISO would you be able to shoot at F8 or is it too dark?

Hi Jon

Well the 7D is obviously a little more forgiving than the 5D so with 15m vis at 15m in reasonably lit conditions you 'should' be ok even if you have to open up to say F5.6. The sweet spot on most of the lenses I've tried underwater is definitely in the F8 - F11 range and although I have shot up at F22 the image does start to become a little soft when really closed up. I'd guess these are going to be some of the same issues with Scarlet/Epic as the sensor is more or less the same size as the 7D. Basically as with everything underwater you have to adapt to the conditions and try to eek out the best shot you can given all the factors being thrown at you!

Cheers, Simon