Formula For Figuring M.O.D.

Can anyone tell me what the formula for figuring minimum object distance and object size when adding diopters? I am planning on using the Schneider Optics Achromatic diopters but don't know which powers to order. I know that I will probably have to stack a +2 and +3 or possibly two +3's to get what I want.

I need to figure out how to shoot some ants where one ant fills the entire screen. I am using a Canon HJ21x7.8BIRS lens on a Sony HDW-750. The M.O.D. of the lens is normally .85m and the objects size at full zoom (164mm) at M.O.D. is 4.6cm x 2.6cm. What power diopter do I have to use to get an object width of 1cm at M.O.D. at full zoom. I know that I can use my 2x extender to get closer, but I'd like to be able to use that to get some even closer shots (5mm object width) of just heads.

Have any of you shot anything this small and this close while it was moving? Is there a better way to do this? How will my DOF be affected? Will by DOF be too small to get anything useful? Any help on this subject is greatly appreciated. Thanks.

Jason White
Producer/Camera/Editor
Audubon Nature Institute
New Orleans, LA

Jason White wrote :

>I need to figure out how to shoot some ants where one ant fills the >entire screen. ....

The books are buried in my basement now, but you might find some useful ideas in nature photography books. The LaRues, John Shaw, and others have published very detailed info on macro photography - including the technical aspects, but the very important wrangling skills you'll need, too.

Ricardo Ismach
Casual Dog Productions

>Can anyone tell me what the formula for figuring minimum object >distance and object size when adding diopters?

Let me risk this calculation :

Minimum focussing distance                      Distance with diopter
--------------------------                           =                 ---------------------
        Image size                                                 Desired image size

.85 / 4.6 = D / 1

Necessary distance will be 18.5 centimetres.

From David Samuelson's manual:

                                             1                                                       1
Necessary diopter   = ---------------             -                  ----------------------
                           Distance with diopter                Distance without diopter

                                                 1                                   1
Necessary diopter =          -----             -                 -----      =      4.2
                                               .185                             .85

In my opinion, this is too close to be working with moving ants. They move very quickly and it is very hard to pull focus on them since at 18.5 centimetres the change in distance is very large as they move past you. It is MUCH better to have a longer lense since the relative change in distance is a lot less for a moving ant. I did my ant work with a 400mm lense and was still only about 40 or 40 centimetres away from them.

The depth of field at this frame size is only a function of magnification and iris so you will not gain any depth of field from working with a wider lense closer in. PCine tells me that at this magnification you will only have about .6 mm of depth of field at f22.

You will need a LOT of light and ants die from excess heat (don't ask me how I know!) so it would be best if you used cooler lights.

Has anyone used probe lenses with this kind of magnification and did they help get more depth of field?

Bruce Douglas, DP
Sao Paulo, Brazil

Jason White writes :

>Can anyone tell me what the formula for figuring minimum object >distance and object size when adding diopters? I am planning on using >the Schneider Optics Achromatic diopters but don't know which powers >to order.

The best source for the detailed DOF info you seek is "Applied Depth of Field", Alfred A. Blacker, Focal Press, Boston, Copyright 1985. Formulas for DOF etc. can be found in David Samuelson's : "Hands on Manual for Cinematographers".

> I need to figure out how to shoot some ants where one ant fills the >entire screen.

You have set a very difficult goal for yourself. Insects, ants especially, move extremely quickly. Unfortunately, I don't believe you will be able to achieve the results you're after with the equipment you describe.

You will need to overcrank to keep them in the frame for more than an instant. You will also need very high light levels to achieve any kind of DOF at that kind of image magnification and frame rate. Ordinary lights = heat. While they are tough little bugs, ants dehydrate (cook) very quickly
under that kind of heat. So you'll need heat filters as well. Extremely stable mounts, etc. It goes on. Be prepared for a very long and arduous journey.

>Have any of you shot anything this small and this close while it was >moving? Is there a better way to do this?

Get a copy of Hotel Haleconia, by list member Phil Savoie. It's incredible. Phil works for the BBC, Nature Films division, and is a great guy; and although I can't speak for him, I'm sure he would be glad to share his experience with you.

I haven't seen him on the list in a while which may mean is off in some jungle doing what he does best.

Brian Heller
IA 600 DP

Bruce Douglas writes:

>Has anyone used probe lenses with this kind of magnification and did >they help get more depth of field?

Get a copy of Hotel Haleconia, by list member Phil Savoie. If you've ever tried to film insects, and it sounds like you have, this is a tour de force.

It's simply incredible.

Phil used every technique in the book and more than a few of his own.

Brian " Savoie Fan Club" Heller
IA 600 DP

Try Briese Sola light fixtures, they're powerful reflective sources, and the heat is a fraction of a spot fixture.

You should get a nice fat stop with no diffusion on the lamp, think photometrics available on website.

Ants have feelings too.
Dan Bronks
DP UK

>Has anyone used probe lenses with this kind of magnification and did >they help get more depth of field?

Go see Bugs! in stereo IMAX. Peter Parks and Sean Phillips (who I've had the pleasure of working with for almost 20 years, now). http://www.giantscreenbugs.com/

Tim Sassoon
SFD Vfx & creative post
Santa Monica, CA 90405

>Go see Bugs! in stereo IMAX. Peter Parks and Sean Phillips (who I've >had the pleasure of working with for almost 20 years, now).

Yes. I've seen it many times, and it is extraordinary. We were actually one of the sponsors of that film.

Last year I talked with one of the producers, and he told me about all of the problems that they had shooting 3D at that scale. I think it might have been a better film in 2D. Nevertheless I'm pretty sure that there were no shots in that film that were to the scale that I am shooting,

Any other ideas?

Jason White
Producer/Camera/Edit
Audubon Nature Institute
New Orleans, LA

>Has anyone used probe lenses with this kind of magnification and did >they help get more depth of field?

I agree with Tim. You should really call Sean Phillips. Even if you did not see the shot you were looking for in Bugs!, I would bet that Sean shot a dozen others as tests. And if not for Bugs!, then he has probably shot something similar to what you need for another project.

Steve Schklair

Brian Heller writes :

> It's simply incredible.

I'll second that!!!

Cheers

Geoff Boyle FBKS
Director of Photography
EU Based
www.cinematography.net