Canon 15mm _ quick FYI

I was trying to shoot some over/unders recently with the Canon EOS1DMKII, Seacam housing, superdome, and 15mm lens. It was an identical scenario to shots I'd done many times before with the same port on a Nikon F100 and D1X with Nikkor 16mm. But even though both Nikon and Canon fisheye lenses cover the same angle of view, they behaved differently though the port.

Using AF, the Nikon lens would pretty well lock on the subject, but the Canon lens was consistently confused by the water droplets on the dome and would lock on there. This could be for several reasons:

1. Closer focus with Canon?

2. Quicker AF?

3. Choice of AF zones?

(Note on close focus - I just researched that aspect and found Nikkor 16mm is 9.84 inches for minimum focus, while Canon focuses as near as 8 inches. No doubt that is the primary reason it focuses on droplets on that particular dome)

For whatever reason it was a hassle. Of course I could have shifted to a single AF point and the odds are I could have targeted that on a distant subject rather than a water drop on the dome. Or I could have gone to Custom Function 4-1 and used the * button. But I found I preferred the control of manual focus. Of course I did not have a MF gear for the 15mm at the time (I do now).

I bring this up only to note the difference between the two cameras/lenses, and to note that Canon shooters may wish to consider a MF gear for the 15mm, if only for over/unders. Underwater of course this is not an issue, and the extreme depth of field of these lenses will handle most compositions.

I have experienced the same with the smaller Seacam fisheye dome + Sigma 15mm fisheye. The lens is able to focus inside the dome (better close focus than canon fisheye, 15 vs. 20cm). So it hunted for water drops sometimes.

For split level shots I set the hyperfocal distance for the intended aperture before I put the camera inside the housing.

Only drawback is I can not change the focus when I want to shoot something different spontaneously.

Therefore I agree, my next housing will have focus gear for that lens.

Julian

Is there a Canon equivalent to Nikon's "Closest subject priority" setting that could be turned off? This sounds like the sort of behaviour a nikon will show if closest subject priority is on.

As I'm sure you know Stephen

Is there a Canon equivalent to Nikon's "Closest subject priority" setting that could be turned off? This sounds like the sort of behaviour a nikon will show if closest subject priority is on.

 

As I'm sure you know Stephen

Very good thought Craig. If I were still on location, without a focus gear, that might have saved some frustration.

Now that I have the focus gear, I think that's the way I'll go. This particular set-up was shooting giant stride enties from water level in rough seas. In situations like that, with the MKII shooting at 8.5 frames a second, I don't want the camera to have to slow down by searching for the intended AF point. The depth of field is so great with the 15mm I should be able to prefocus and go. The other advantage is to be able to cheat the focus between the topside element and the underwater subject in the hopes of getting both sharply focused.

Looks like I will need to add the focus gear to my order...

Thanks for the info Steve.

Keith

Interesting comments re: the Canon 15mm fish. I'm pretty sure it's got the old non-usm motor, so you'd have to commit to manual focus predive if you're using a focus gear.

Having just been shooting at 17mm non-fisheye focal length this weekend, I've decided 17mm really isn't as wide as I'd like on the 10D. I've already got my 15mm fisheye dome, just haven't bought the lens yet.

I have been a bit concerned re: reports of focus problems with the Sigma fish. The closer focusing does sound attractive, however.

Anyone want to add their experiences with the Canon or Sigma variants?

Hi Rob,

focus problems with Sigma 15mm? Never had one / heard of it.

what kind of problem should this be?

I have tried both and couldn't figure out any major differences in image quality.

I am very satisfied with the Sigma fisheye. It's housed behind the Seacam fisheye dome. closer focusing was one reason for my choice. And as you say the Canon does not offer USM advantage, so I went for the Sigma finally.

Especially with small domes the closer focusing could also be important.

Julian

I've read reports on another site of difficulty obtaining focus lock with Sigma (this was above water). BTW, I'm not saying that there is an issue with focusing (as I don't believe everything I read online, with the exception of wetpixel ), just that I'd read about it and therefore was interested in user's opinions. I know several people on this site use the Sigma. It's a little bit cheaper, though not a lot. I tend to use Canon lenses where possible, unlike you Jolly...you really need to swap your 10D for a SLR/c so you'd have the full Sigma kit!

Hi Rob,

just can say my copy of Sigma 15mm lens focuses well, no probs.

I am/was strongly Canon minded in terms of lenses. I am sure there is no better choice when it comes to my 100-400L IS USM or even the versatile use of the 28-135 IS USM and a lot of others.

The downside is, Canon does not build wideangles for the 10D. Without intention, Sigma was growing in my lens bag. Also the 1:1 Macro was the better choice to me. I hope you will accept my efforts of excuse?

Yes, a very wide lens like the 15mm fish is often harder to focus in comparison to longer focal length. The DOF is so big that the AF system simply cannot find a sharp gap as with "normal" lenses. A fisheye is a real good lens for manual focus and/or hyperfocal distance focus.

But the AF of course works without any problems. No focus hunting or anything like that. I have tried both and didn't notice a difference in terms of AF.

You think, Kodak/Sigma/Peling would build me one with canon mount? :wink: