auto focus struggaling

[steve-k 0]

i have a canon20-d, ikelite housing, 1 d125 strobe, using a 60mm2.8 and the standard 19-55mm

 

on the 60mm the unit seams to struggle to AutoFocus? at 0-10m it gets 60% 10-20m 25% and below 30m i can forget it

it does a bit better on the 18-55 but not much,

he camera tries to focus at the end of its distance range but wont hunt back? i am finding that i have to focus on somthing 2/3 m away with high contrast then try again at the closer object

the camera works on land, and in low light

i have had the camera on sutter priority, and tried just the center spot focus point

 

is this common? (yes i am new) any ideas?

 

also off the 60mm all the shots are a bit hazey (ok with the 18-55) i had put this down to not being on focus, but the camera focused on somthing, and no part of the shot is clear?

 

 

i am thinking of getting the 17-85 is lens and the dedicated port with the M focus controle, is this a good allround choice?

 

 

lol 2k spent on housing and i have had much better results from my old crapy 2meg instamatic and housing with built in flash

[Alex_Mustard 0]

Hi Steve,

 

I am not a Canon user - but lots of people successfully shoot that lens. I'd also encourage you to perservere with your setup - as it is certainly very capable. As far as I know, one of the world's best underwater photographers, Doug Perrine still uses (or at least used for a long time) the 20D. So there is nothing wrong with your kit - it is like any technology that offers more control it takes longer to get used to it.

 

The trick with autofocus is not to expect it to be a magic on off switch. You have the help the autofocus lock - by placing the autofocus sensor over areas of colour and contrast onto which it can easily lock.

 

And the best way to learn what your camera likes and does not like is by using it. As general rules try and keep the AF sensor on well lit areas of your subject (not on areas in shadow) and also place it over points of contrast (the eye - rather than on a monotic area of colour)

 

The other solution is to add a focus light - which will help it greatly.

 

Alex

[imasleeper 0]

I'll take a stab at this as I did use a 20d in an ikelite housing until moving on to a 1dsII.

 

1. If you have the autofocus set to servo or continuous mode consider setting it to single shot.

2. If you like using the shutter priority mode try using the upper end of the shutter speeds (1/125-1/200) as

opposed to the lower ends 1/30-1/60.

3. Consider using full manual, you're half way there already.

 

When set to single shot the camera will not take a picture unless it is in focus whereas in servo mode it will....the thinking being that a slightly out of focus shot is better than none at all. It's amazing how much we "move" underwater even when trying not to and by increasing the shutter speed some if not all of the softness you notice in your pictures will improve.

 

4. There is a modeling light on the ds125, consider using it. However you will find that under low contrast

conditions, the use of a dedicated modeling light will greatly lessen the "hunting". I use(d) a fisheye---

actually now two of them.

5. Using a single focus spot as opposed to all 9 is correct. This will lessen the hunting. Also remember you

can pick which one which can help with composition.

6. There is always manual focus as you are considering, however I never found that necessary and with my

poor eyes not practical.

7. Stategy wise I would try and keep the camera closely focused during a dive. By that I mean I would

intermittently point the camera at the reef and half press the shutter button causing it to focus. Now if

something cool comes along at least I am always in the ballpark and the camera doesn't have as far to

go to achieve autofocus.

8. Lastly keep trying, you will get better.

 

Hope you find this helpful,

cheers

 

imasleeper

[steve-k 0]

thx for the replies

 

on the 60mm lens i have had the aperture wide open, the depth of field has been only very small, i did not think this would affect the AF, but goes some way to explain the haze of the shot, on my chart it says dof should be about 100/200mm at 1m, but on the shots its only getting 20/40mm,

 

i tried the modeling light and found no difference, i was expecting to be able to use the modeling light in caves, under rocks etc, i have a 100w HID dive torch (amazing light output) and it still struggles with that?

 

i use one shot focus

 

i will give full manual a go keeping the speeds to 125/200 and maybe f5.6/f8 and let the d125 earn its money

 

but i don't see how this will help the AF?

could the wrong port affect the AF?

 

i got the 60mm for this purpose only, i am finding it restrictive(i like zooms)

i am still going to go for the 17-85, as i want a walk around land lens (my existing lenses are very heavy) and i can get the dedicated port, anybody use this lens?

 

will let you know if i get better results

steve

[imasleeper 0]

another thought----do you have the on board camera flash and the auto assist beam turned off. You do this in the custom menu, I think it is #5 and #7. If not, consider doing so as there maybe some interference between the lens AF and the IR AF assist light due to the fact the camera is in a housing.

 

You've probably thought of this already, but I forgot to mention it in my previous post, sorry!

 

imasleeper

[steve-k 0]

another thought----do you have the on board camera flash and the auto assist beam turned off. You do this in the custom menu, I think it is #5 and #7. If not, consider doing so as there maybe some interference between the lens AF and the IR AF assist light due to the fact the camera is in a housing.

 

You've probably thought of this already, but I forgot to mention it in my previous post, sorry!

 

imasleeper

 

the af asist beam is on, i will try it off, not thaught of that thanks

[dmoss 0]

Steve

 

I would have to second Alex's comments. Use the center focus point and move the camera around a little and lock onto an area with contrast. The 20D is a very capable camera.

 

I have both the 60 and 17-85 so I'll give you my take on the lenses.

 

I consider the 60mm my favorite lens. For me it focuses extremely fast and it is my lens of choice for night dives. I use a focus light at night but seldom need one for daytime. I assume you are using the 5502 port with this lens. Keep practicing and soon you will automatically set the focus point on a point of contrast, then recomposing.

 

On the 17-85, the special 5503.90 port has an external knob that operates the zoom control. It won't operate the manual focus ring. I really like this lens when I'm not sure what I'll find on a dive. Works well for fish portraits and reef scenes. You will need a good +4 diopter with it as it doesn't focus very close to the camera. Also, the port has a nasty habit of tripping the AF/MF switch on the lens when you slide it over the lens and attach to the housing. Make sure you check to confirm the autofocus is working before you jump it. You can't see the switch with the port installed.

 

As imasleeper noted, on the 60mm, any movement on your part once autofocus is locked and using a wide open aperature will result in a blurred image. When I'm shooting macro, I'll normally take 6 to 10 pictures of the same thing just to be sure I'll get a sharp one.

 

The only time you should be concerned about the camera on-board flash is if you are in full auto mode. In full manual or shutter/aperature priority the flash won't automatically pop up.

 

Hope this helps.

[steve-k 0]

thx again for all the help

 

i have checked again at my previous pics i took with the 60m, the blurred images (all lol) are down to the very small depth of field

 

is this lens only for macro work?

 

i tried it in the pool yesterday and even at f8 the dof is very small, what fstop do you shoot at normally, and at what distance

 

i have tried focusing on high contrast areas, and using the assist light, but it just would not focus, i did have the assist beam turned on, and multi point focus on, and the lens wide open,

 

 

on land i know to take a good shot, i have to slow down and act and think like a photographer not like a tourist, unfortunately i am not adopting this practice underwater, i have been a diver with a camera taking snap shots, we know at this level i have to think like a photographer, who happens to be underwater

 

i will get back in the water this week with the 60mm and see what improvements i can make

 

thx again for all your help

 

steve

[steve-k 0]

went out today, thunderstorm, dark dismal, and crap vis lol

 

but i have had the 60mm focacing fine

 

had it set on 160 anf f13 with the strobe on ttl, ignoring the crap compsition and scatter, the pics where in focus and sharp

 

still supprised what little depth of field you have, even on f13

the lens will close down to f32, what do you normally use on close up work?

 

i think my main problem was not having the focus set on a single point

 

thx again for all the help

 

steve