D70s focus

Hi

Hope you can help me

I have a D70s DS125 and ikelite housing (first time using it so its still a bit hit and miss)

Just returned from sharm and have a lot of photos out of focus

First day I had it set on AF-s to try to ensure the camera would not fire unless it was in focus. I turned this off (set it on AF-c big mistake) because the camera would not achieve focus. I.e. stone fish just sitting there, the camera can not achieve focus on a reef why??

It was pot luck as to getting focus lock or not getting it

So I put it on AF-c

yes I now know it takes the picture but unless I had large f number the pis are out of focus

so what is the best way ??

what settings do you have your camera on ?

AF-s seems the best way if you can get the camera to achive focus

any ideas etc hope you can help me

bit dissapointed had a big turtle sitting slap bang in front of the camera it was even smiling for me and the pics are slightly out of focus ( I was eye ball to eye ball with it on my own one of those shots you will never get again!)

Rgds + thanks

Hmmmm. Well, we first need to know what lens you were using, What Lens port, and if you were using a Diopter or not.

Lenses that can not focus on there own < then 12in from the Film Plane need to use a close up diopter +4 to achieve Focus in a dome port. This is because a dome port ( underwater ) acts like a big lens bringing everything to focus at around 12". See Ikelite.com port selections for an explanation of this.

Bill Russell

I had the same experience the first time I used my D70 in an Ikelite housing with the 18-70 kit lens. I was very disappointed with my new set up after that first trip

I did some checking when I got home. I did not have the +4 diopter recommended by Ikelite on their lens port web page.

After I added the +4 diopter the lens focused with no problems B)

I usually shoot in AFS.

I use AF-S as I struggle to get a lock with AF-C but many people prefer AF-C so I guess it's just a matter of practise.

My guess is that you're using something like the 18-70mm kit lens which doesn't focus close enough to work behind a dome port unless you add a diopter to the front of the lens. If this is the case it'll work fine on the surface but will never be able to focus below water.

The curve of a dome port acts as a lens so that the furthest subject from your camera wll only ever appear to be 12" away from the camera. If your lens cannot focus this close then it just can't focus.

The 18-70 definitely needs a diopter, +4D is good. The more expensive, thinner lenses are better. I'm not familiar with Ike's domes, but a dome that can accomodate a wider angle lens is useful as focussing is less of a problem: the 10.5mm is fantastic, though I went through similar focussing problems with an old 16mm lens which wouldn't focus until the rear filter was removed (optics is meant to be logical, but dome optics seems to be a black art!). Compatibility of lenses and domes is very important, and I've been caught out by not seeking specialist advice first, and trying to deal with problems when I've already bought the kit...

AF-C is tricky, especially if you are working with a moving target and the lens is slow to focus. I find AF-S much better, and just keep popping the shutter at moving fish.

Tim

B)

Hi all,

I too have a new D70s setup and use a +4 diopter (BW), with the 18-70 mm kit lens. I was also disappointed with my first outings; even the carefully composed, still subjects using autofocus (AF-S) didnt have that really crisp look you might expect from such a camera.

Is the 18-70 mm lens considered a mediocre one? I noticed the greatest focus problems came at the 70 mm zoom end. Is there some other setting I could be making a mistake with?

I use an Ike housing with the recommended dome port for the lens, using settings around 1/200 shutter and f10.

HELP!

Cheers,

Ash

The 18-70mm is not as good as the 12-24mm, although a year ago there was a lot of disappointment about the 12-24mm, which really needs a carefully matched dome. I wonder if there a some subtleties that give rise to problems, although it could be that I'm not critical enough of my images.

What I do, if it's any help is:

1) work in manual, mostly: 1/60 - 1/125 at f8 - f11

2) use strobes

3) use spot metering and a central, fixed focussing area on AF-S

4) often focus and shift the centre of the image with the focus locked by half-depressing the shutter release

5) for fast moving fish I get as close as possible, put the fish in the middle, and crop in Photoshop if that improves the composition

I experimented with both +3D and +4D on the 12-24mm: possibly +3D is marginally better. I use +4D on the 18-70mm lens, but have to admit that I don't use the lens that much.

In the uniformly excellent third edition of "The Underwater Photographer" by Martin Edge (Focal Press, 2006) he describes a common error, that of zooming to fill the frame and not getting closer, and longer lenses tempt us to do this. My personal solution is to use a 10.5mm lens as much as possible, but, then, I do like wrecks and reef scenics and I've yet to buy a macro lens and a flat port.

I'm not sure that the resolution of web images demonstrates this, but the moray was taken from further away than the coral grouper, and isn't as sharp:

Tim

B)

Oh...

... and both with the 18-70mm and +4D B+W diopter.

Tim

B)

Thanks Tim,

Very comprehensive. Nice shots, too! Your images show that this lens can, indeed, take beautiful shots. I have a few shots of my own that have worked. It seems to be more a matter of consistency. I can shot 150 shots with this lens, may get 5-6 keeper shots (and yes, I am fussy about sharpness!). I think it is time for me to upgrade my lenses to 10.5 mm and a 60 mm macro.

All the best,

Ash

We have a D70 with the 18/70mm lens and have screwed on a number #4 diopter onto the end. Seems to work okay.

Here is a cropped pic Kelly my partner took with it on, she is still learning...

Hi waqsy,

Very nice pic. What type of housing is Kelly using? I am curious about port quality, also.

Cheers,

Ash

This one

No dome just a flat port.

Sea & Sea