Film types and speeds

[joewr]

Originally posted by scorpiofish


You need to rethink the statement that 400 speed film would allow for greater depth of field. The speed of the film has nothing to do with DOF directly. DOF is controlled by the aperture size. Indirectly, the faster film would allow the same exposure with a smaller f-stop, which would allow a greater DOF. Of course, this in turn would negate the advantage of a faster film increasing light exposure to the film.

Scorpiofish,

I do not mean to be overbearing on this, but the shutter speed, aperature opening and ISO are all interrelated. So, if you increase the ISO you can increase the depth of field by decreasing the aperature opening. Or you can increase your ability to stop action by increasing the shutter speed. Those are direct effects of increased ISO.

I am not certain what you mean by "negating the advantage of a faster film", though. Those are the two advantages to faster film: you can stop down the aperature or you can increase the shutter speed. Or you can do both if there is enough latitude in the higher ISO. So, for example, you could use ISO 400 instead of ISO 100 and stop the lens down one f stop and increase the shutter speed by a factor of 2. That would give you a total factor of 4, consistent with "proper" exposure.

Remember, just because you increase the film speed does not mean the only variable you can "play with" is shutter speed!

Joewr...

 

[syruss32]

Okay all you camera buffs don't bash me, this is a newbie question.

I have a sea and sea mx-10 no extra lenses, just the built in one and the YS-40 strobe. If I put in 100 speed film and am taking pictures at say 3 foot range what should the f/stop ideally be.

I am looking for general setting till I get more practice and some books on u/w photography.

 

[joewr]

Syruss,

I would suggest that you dig a little deeper into your pocket and get the 20mm conversion lens.

Why? Because it has a greater depth of field (= to how much is in focus)--i.e., you can have a greater latitude of "misfocusing" and still have what you are shooting in focus.

For example, at f/8, a good place to start, the lens you have on your camera when focused at 3 feet, will have things from ca. 2.6 ft to 3.8 ft in focus. If you went to the 20mm the things in focus would be 1.75 ft to 10.5 ft.

Now, your flash will probably not cover the whole range given you by the 20mm, but it will allow you more latitude.

At f/11 you will have the following depths of fields:

32mm lens--ca. 2.5 ft- 4.1 ft

20mm lens--1.6 ft-infinity

But whatever lens you use, I think that f/8 or f/11 would be a good place to start. You can then judge when you get the prints back how you are doing. Take some shots of the same scene--you like coral, right?--and vary the aperature at the same focal distance. It is worth a roll (and more) to get a fix on how the camera works. Take notes or just remember what the settings were--this is sorta like plan your dive, dive your plan stuff...

Joe Liburdi has a book out on the use of Sea & Sea cameras and other equipment...I recommend that you have a look at it, too.


Joewr

 

[Dee]

Now that I know you have a MX-10, Joe Liburdi's book "The Complete Guide to Sea & Sea" is exactly what I would recommend.

I used the same camera for several years until I upgraded to the MMII. f/8 and f/11 are good places to start. If you have a reflective background, like a snad bottom, or a really bright reflective fish, like a Barracuda or Tarpon, use f/11.

Joe said...

Take some shots of the same scene--you like coral, right?--and vary the aperature at the same focal distance.

That is called bracketing. If you bracket between f/5.6, f/8 and f/11, one of those shots will be the right one. You'll soon get to the point you'll just 'know' which one to use!

If you have one of the newer MX-10's with the tripod whole on the bottom, you can attach a strobe base to it and either move the YS-40 strobe away from the lens and angle it to avoid the backscatter. You can also add a seconf strobe for extra coverage when using a wide angle strobe. If they had had this feature back when I used mine, I would never have replaced it!

 

[syruss32]

Originally posted by Dee
If you have one of the newer MX-10's with the tripod whole on the bottom, you can attach a strobe base to it and either move the YS-40 strobe away from the lens and angle it to avoid the backscatter. You can also add a seconf strobe for extra coverage when using a wide angle strobe. If they had had this feature back when I used mine, I would never have replaced it!

It does have that tripod hole. Do they make an extension for the YS40? or do I have to go with another strobe?

 

[joewr]

Syruss and Dee,

I am a (I guess, obsolete) Nikonos user, but as I remember the MX10 uses an infrared system to fire the stobe. Therefore you would have to be careful if you moved it off its normal mounting position. However, I suppose you could use the threaded hole to mount a tray for a slave strobe and use the TTL feature on the MX10 to control exposure...

While backscatter is a problem with a single strobe pointed straight ahead, I think that the very shallow depth of field provided by the 32mm lens is a bigger problem. Syruss, since you are in the neophyte stage of your u/w photography career, I would suggest that, if you do not want to spring for the 20mm conversion kit, you use ISO 400 film. Then you can stop the lens down to f/16 or f/22 and get all sorts of things in focus:


f/8--depth of field = ca. 2.6 ft - 3.8 ft

f/11--depth of field = ca. 2.5 ft - 4.1 ft

f/16--depth of field = ca. 2 ft - 4.8 ft

f/22--depth of field = ca. 1.5 ft - 5.2 ft

Another thing you might consider is to focus at 4 feet:

f/8--depth of field = ca. 3.2 ft - 5.0 ft

f/11--depth of field = ca. 3 ft - 5.5 ft

f/16--depth of field = ca. 2.8 ft - 7.2 ft

f/22--depth of field = ca. 2.5 ft - 10 ft

This is another form of "bracketing" that can be used underwater. For fish, it is usually difficult to get as close as 2 ft when you are just beginning to take u/w photos and, so, with ISO 400 film at f/16 there is a better chance to get good photos.

That is also the "value" of depth of field: you do not have to be precise in focusing; you have to be semi-precise. That is, just precise enough to catch everything you want within the depth of field range.

Now, that said, I have "portraits" of fish that I have taken with a macro setup that required me to get within inches of a fish. So it is doable, but I had to learn what fish had a tolerance for humans getting close. For example, some eels will let you touch them with the lens! I even had one chew on the aiming bar of my extension tube setup once! However, most fish are a little less tolerant.

Joewr...

 

[Dee]

Originally posted by syruss32


It does have that tripod hole. Do they make an extension for the YS40? or do I have to go with another strobe?

Yes, 'they' make a fiber optic cable that will allow you to move the YS-40 away from the camera. I know one fellow that sells one but it's sort of expensive. http://www.gbundersea.com/ However it's cheaper than a second strobe.

The only problem I see is attaching the strobe to the base plate. I'm sure they've thought of a way to do it. Guess you could always use zip ties and tie it to a regular strobe arm!

This definitely requires a bit of research.

 

[joewr]

Dee,

I checked out the website and it seems that the have the bases for both old and new MX10s as well as the fiber optic connector. Looks like a good gadget to have!

Joewr

 

[Dee]

Thanks Joe. I haven't been to Greg's site in awhile. I'm a big believer in his Save-A-Lens kits and use them on both the MX-10 and MMIIex. For anyone using S&S cameras and changing lenses underwater, it's very cheap insurance against dropping one!

 

[scorpiofish]

Typical rule of thumb for the MX-10 with standard lens:

Sunny, <60ft. f/8
Cloudy <60ft. f/5.6
>60ft. f/5.6

With bright background, e.g. reflective sand, close down one f/stop, e.g. go from 5.6 to 8 (higher number).

The MX-10's minimum focus distance is with 32mm lens is 4ft. This gives you a very small window. The value of the 20mm lens cannot be underestimated. It reduces your minimum focus distance and allows you the same shot with less water column between you and the subject.