December 22, 2014, 06:40:15 AM

Author Topic: Over - Under -shot not in focus?  (Read 7663 times)

fiend

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Re: Over - Under -shot not in focus?
« Reply #15 on: September 24, 2013, 07:43:59 PM »
Manual Focus, only way.

If you Auto Focus your Focus Point will pick up what ever it's locked onto, underwater area/above water area, you have to Manual Focus for the best compromise between the Underwater section & Above water section.

Another trick is to wipe your Dome (The Housing Dome, not your other dome), with "Rain X Glass", helps make the water droplets not stick to the Dome and becoming a problem with blurry spots in the Image.

Over/Under shots done well are a bit of a suck & sea, lots of practise, but always with Manual Focus, f/16.

I use a Seacam Housing with a 5DMKIII + 8-15f/4 or 24f/1.4, 8-15 @ 15 & f/16, the 24 @ f/16.

Have a look at some of "Lemmyshowyou"s Images on the 1Dx site, maybe PM him and I'm sure he will gladly give you some more advise.

You can't focus on something in the water then?
Manual focus.. so what should I focus on? Then I have to manually focus before I put the lens into the housing but then I can only use the setup for under/over-shots and not for general underwater shots aswell?

I use back button focusing so I don't have to think about the camera "refocusing" when I'm shooting the shots.

Rain X Glass? You can't use just some soap or something that repells the water or makes it more "slick" ? :)
Don't know if Rain X Glass is a product that is available in Sweden where I live.

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Re: Over - Under -shot not in focus?
« Reply #15 on: September 24, 2013, 07:43:59 PM »

privatebydesign

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Re: Over - Under -shot not in focus?
« Reply #16 on: September 24, 2013, 08:00:31 PM »
What lens, port, housing, tube etc?

Canon 5D mk3
Sigma 15mm/2.8 Fisheye
IKELITE housing
IKELITE dome 8" + wide angle adaptor/tube so no vinjetting.

Is the tube part number "#5510.11 port body"?

fiend

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Re: Over - Under -shot not in focus?
« Reply #17 on: September 24, 2013, 08:01:47 PM »
What lens, port, housing, tube etc?

Canon 5D mk3
Sigma 15mm/2.8 Fisheye
IKELITE housing
IKELITE dome 8" + wide angle adaptor/tube so no vinjetting.

Is the tube part number "#5510.11 port body"?

Yes :)

privatebydesign

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Re: Over - Under -shot not in focus?
« Reply #18 on: September 24, 2013, 08:13:33 PM »
What lens, port, housing, tube etc?

Canon 5D mk3
Sigma 15mm/2.8 Fisheye
IKELITE housing
IKELITE dome 8" + wide angle adaptor/tube so no vinjetting.

Is the tube part number "#5510.11 port body"?

Yes :)

OK, you have the correct port extension, but you should still have some vignetting on the ff 5D MkIII. Anyway,  as a start f4.5 is way inadequate, as eml58 says try f16 and I suspect your problems will be gone.

If not it will take some fiddling, put lens in manual focus and focus on the overwater section, take the housing out of the water dry off the port and take it off to see where you focus is, make a note, then do the same thing with the underwater part. You will end up with two figures, make sure you use dof/aperture value that comfortably encompasses both figures. Done.

fiend

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Re: Over - Under -shot not in focus?
« Reply #19 on: September 24, 2013, 08:31:46 PM »
OK, you have the correct port extension, but you should still have some vignetting on the ff 5D MkIII. Anyway,  as a start f4.5 is way inadequate, as eml58 says try f16 and I suspect your problems will be gone.

If not it will take some fiddling, put lens in manual focus and focus on the overwater section, take the housing out of the water dry off the port and take it off to see where you focus is, make a note, then do the same thing with the underwater part. You will end up with two figures, make sure you use dof/aperture value that comfortably encompasses both figures. Done.

If you look at the full res picture you can see that there is no vinjetting or at least as far as I can see :)
Might be a little darker in the corners but that's not bad.
I will try f16 and see if it will be better when I try to shoot with a smaller aperture.

Then I have to be at the correct distance to the object before I put it in the housing? Since I can't manually focus when it is in the dome.

Lets see if I understand it right.
I focus on the object that I want in focus ABOVE the water.. check the reading.. like 1m
Then I put it down in the water and to the same and check the reading.. and I get like 0.3m
Then what? :)

I've attached a picture of the lens with the focus set on 0.5m (focused under the water).
How can I know the aperture/focusdistance to the "over"-object with this? :)


privatebydesign

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Re: Over - Under -shot not in focus?
« Reply #20 on: September 24, 2013, 09:14:43 PM »
Ok imagine over distance is ∞ and under distance is 0.5m, where I put the two arrows, turn your focus so the two arrows are equal distance from the focus line, the small numbers below, 8 in this case, are the minimum dof needed to encompass both over and under, but I would recommend at least f11.

Here is your picture edited, I have moved the focus ring to where you would need it to be with the above numbers.

fiend

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Re: Over - Under -shot not in focus?
« Reply #21 on: September 25, 2013, 06:05:09 AM »
Ok imagine over distance is ∞ and under distance is 0.5m, where I put the two arrows, turn your focus so the two arrows are equal distance from the focus line, the small numbers below, 8 in this case, are the minimum dof needed to encompass both over and under, but I would recommend at least f11.

Here is your picture edited, I have moved the focus ring to where you would need it to be with the above numbers.

Aaah, sweet! :) that explains it! Sounds good. Is the distance "below" equal to distance above?
I've read something about an "virtual image" that you focus on so the distance below is not the same as above.

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Re: Over - Under -shot not in focus?
« Reply #21 on: September 25, 2013, 06:05:09 AM »

Drizzt321

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Re: Over - Under -shot not in focus?
« Reply #22 on: September 25, 2013, 01:05:52 PM »
Ok imagine over distance is ∞ and under distance is 0.5m, where I put the two arrows, turn your focus so the two arrows are equal distance from the focus line, the small numbers below, 8 in this case, are the minimum dof needed to encompass both over and under, but I would recommend at least f11.

Here is your picture edited, I have moved the focus ring to where you would need it to be with the above numbers.

Aaah, sweet! :) that explains it! Sounds good. Is the distance "below" equal to distance above?
I've read something about an "virtual image" that you focus on so the distance below is not the same as above.

The search term you're looking for is Zone Focusing, or Scale Focusing (https://en.wikipedia.org/wiki/Scale_focus, http://digital-photography-school.com/ultimate-guide-to-zone-focusing-for-candid-street-photography). I've become better at it since getting my 120 folder that I have to set the focus manually on the lens before using the viewfinder to approximately frame. Unfortunately most lenses these days don't have any kind of decent focusing scale, although with a fisheye like the one you have unless you're just a few feet from the lens you can pretty easily get acceptable focus to infinity stopped down a fair amount.
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privatebydesign

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Re: Over - Under -shot not in focus?
« Reply #23 on: September 25, 2013, 01:58:32 PM »
Ok imagine over distance is ∞ and under distance is 0.5m, where I put the two arrows, turn your focus so the two arrows are equal distance from the focus line, the small numbers below, 8 in this case, are the minimum dof needed to encompass both over and under, but I would recommend at least f11.

Here is your picture edited, I have moved the focus ring to where you would need it to be with the above numbers.

Aaah, sweet! :) that explains it! Sounds good. Is the distance "below" equal to distance above?
I've read something about an "virtual image" that you focus on so the distance below is not the same as above.

No the distances are very different, because of the "virtual image". Underwater the water and port combine to make a lens that makes everything seem much closer to the camera (it creates a "virtual image"), over water the dome is just a piece of clear plastic and does not affect focus distance.

So you need a dof that covers both actual (above) and apparent (underwater) distances, even when they are the same physical distance from the camera.

Typically a domed port underwater will focus at 1- 1 1/2 times its size, but this is vary variable depending on focal length, distance from lens to port etc etc. So your 8" port will focus at infinity at around 8"-12"! However the above water portion of the image will focus normally. As you can see you need massive dof to cover both these figures.

Drizzt321

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Re: Over - Under -shot not in focus?
« Reply #24 on: September 25, 2013, 02:02:45 PM »
Ok imagine over distance is ∞ and under distance is 0.5m, where I put the two arrows, turn your focus so the two arrows are equal distance from the focus line, the small numbers below, 8 in this case, are the minimum dof needed to encompass both over and under, but I would recommend at least f11.

Here is your picture edited, I have moved the focus ring to where you would need it to be with the above numbers.

Aaah, sweet! :) that explains it! Sounds good. Is the distance "below" equal to distance above?
I've read something about an "virtual image" that you focus on so the distance below is not the same as above.

No the distances are very different, because of the "virtual image". Underwater the water and port combine to make a lens that makes everything seem much closer to the camera (it creates a "virtual image"), over water the dome is just a piece of clear plastic and does not affect focus distance.

So you need a dof that covers both actual (above) and apparent (underwater) distances, even when they are the same physical distance from the camera.

Typically a domed port underwater will focus at 1- 1 1/2 times its size, but this is vary variable depending on focal length, distance from lens to port etc etc. So your 8" port will focus at infinity at around 8"-12"! However the above water portion of the image will focus normally. As you can see you need massive dof to cover both these figures.

Ah, that's what he meant by "virtual image", interesting. Good to know.
5D mark 2, 5D mark 3, EF 17-40mm f/4L,  EF 24-105mm f/4L IS USM, EF 135mm f/2L, EF 85mm f/1.8
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Lyle Krannichfeld

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Re: Over - Under -shot not in focus?
« Reply #25 on: July 21, 2014, 08:08:16 PM »
Hi there, old post but worth posting.

Some quick tips:

Camera on manual
f16 or as close as you can get
Expose for the above
Focus below (either on manual focus or AF, you can pre-focus and re-compose, or select the lower AF points)
If you don't have a lot of light in the water you'll need strobes to bring in detail and even things out, and in this instance you generally need a LOT of light due to the wide angle. I use 2 older DS125's (now 160's) and they are usually on close to full power for over/unders.

I don't suggest Rainx. Spit works (spit on it before you get in, wipe it around and let it dry). Lasts 30 minutes or so with good results. Or slice a potato and wipe it around before getting in.

Lyle
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Re: Over - Under -shot not in focus?
« Reply #25 on: July 21, 2014, 08:08:16 PM »