F stop question

[airdrew20012001 0]

anybody ever monkey with F-stop during freefly stuff? How did the photo's turn out?
Drewfus McDoofus

[quade 4]

f-stop controls depth of field. Depth of field is the amount of area closer or further away from the camera that is in "acceptable" focus from the point that is in the sharpest focus.
If you wanted to make a photo with everything in focus from the closest object all the way to the horizon, then you'd need a very small f-stop.
This confuses people so pay attention here. The higher the f-stop number, the smaller the opening and greater the depth of field.
Opening the f-stop to a smaller f-stop number, will allow more light into the camera, but will decrease the depth of field.
f-stop and exposure time are inter-related. Closing the f-stop one full stop requires you to double the exposure time for the same amount of photon to hit the film and be exposed at the "same" light level.
By playing f-stop against film speed and exposure time, you can create motion blurs or throw the background out of focus.
Please see attached photo for an example of a photo taken with a longer exposer and wider f-stop.
Notice that the subject in the photo is in fairly sharp focus, but the background is pretty much out of focus. This draws attention away from the background and toward the subject.
quade
http://futurecam.com

[CameraGeek 0]

Perfect explanation.
I've played around with depth of field a lot in RW photography and every where I else I shoot. It adds a lot to any photo but in skydiving especially it can make a special moment even more unique by isolating the subject and basically removing the background from notice.
To use depth of field you usually have to look at your lens to understand how to set it up. If you're lucky, along the top there will be some colored marks on either side of the place where the f-stop and focus cross. (Look at your lens or I'll lose you here!)
Again - you have to look straight down at it with the lens pointing 90 degrees away so you see the focus ring and f-stop setting (manual focus cameras may be best for this).
Okay - on each side there may be colored lines or "tick" marks evenly spaced out from the center - ON EACH SIDE of where you set the focus and the f-stop.
Now - again, if you're very lucky - the numbers that correspond to the f-stop (i.e. 5.6, 8, 11, 16) may also correspoond to a color of those....tick marks I mentioned.
If you have that, and follow me, all you have to do, is set the distance to the subject within those colored tick marks to be in focus.
I use 1/500 at f 8.0 almost religiously. (ASA 100 Color Print)
To use depth of field I just set the "infinity" focus mark OUTSIDE of the colored tick marks, and ensure that the distance from me to the formation is WITHIN the tick marks. You can do that. It works.
If I didn't lose you then maybe just go shoot a roll in the backyard as described perfectly by the moderator. Play with the focus only for a few frames, then change the f-stop only for a few frames - shoot 24 exposures and you'll get the idea very quickly.
Better yet - if you own a digital camera with manual controls, the same principal works. (Digital camcorder or still camera)
I attached a small example of a photo I took in my backyard that is a great example of depth of field.
Hope that made sense
Robbie Culver

[CameraGeek 0]

about that attached file....

[flyingferret 0]

Excellent explanation. Here is a handy link:
http://javascript.internet.com/calculators/field-depth.html --- very sweet calculator for depth of field
I tried to find I nice little page explaining how the 'f-number' is an expression of a ratio between aperture and local length. It is not too intense math and once you see it, it makes a lot of sense. But I could not find any good links quickly.
Anyway, I highly recommend experimenting with aperture. I have not done it in freefall as I am shooting video only, although actually, those AE program settings alter aperture and shutter speed on a digital camcorder. But in aperture control is still one of the things that I find truly amazing about photography...the beauty of how it all works together. Working with macro tubes I have created some awesome shots with of depth of field maybe 1/4 or 1/2" Very neat stuff to play with.
Malachi