Quick question on focusing

[millertime24 8]

Can anybody tell me how to focus on 2 objects at the same time while they are different distances away with a dslr. The book that came with my camera said something about "depth of field" but doesnt really go too far into it.

Muff #5048

[DSE 3]

A super broad answer:
Wide aperture=shallow depth of field
Narrow aperture=broad depth of field.

You can download many free DOF (Depth Of Field) calculators based on Java.

Google circle of confusion, or better still, come see me at the DZ. Bring your camera.

http://www.luminous-landscape.com/tutorials/dof2.shtml has a good picture set on the subject.

[PhreeZone 15]

Do an online seach for Depth of Field. It changes for every f Stop and lens. Specifically look up hyperfocal distance also. This is another key term you will need to figure out use for shots like this.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[millertime24 8]

Awsome. Thanks. When does your DZ open back up anyway?

Muff #5048

[DSE 3]

Looks like next weekend, weather permitting. We would have been jumping this weekend, had we known the weather was holding at 50. Me? I'm heading south for the weekend.

[HSPScott 0]

Hey DSE,

If you are ever in the Austin area, give me a shout.

Scott

[millertime24 8]

Ok so I tried experimenting with it last night. My grandpa is a pretty big camera enthusiast so he was talking me through it on the phone. What ended up working was an fstop of 27 on app priority (I was shooting a leangth of fence post). The only thing is your exposure time is anywhere between .5 all the way up to 2 sec depending on lighting and at that kind of distance the dinky little flash on the camer is of no avail. I used my tripod and acually got some pretty decent photographs (sorry about not posting them but I didnt bring my cam to work today). Anyhow, thanks for the help. That website set me in the right direction.

Muff #5048

[pattersd 0]

Depends on the camera.
You can do it manually like you did, or on some cameras there is a shooting mode that will try to determine what you want. on the canon dig rebel xti it is called A-Dep, when in that mode you get the focus points to cover what you want to be in focus and the camera will determine the aperture that will give you the correct depth of field. trying to cover a fence post with the focus points would be a pain, so manual mode would be easier.
on a different camera I have you set it to the mode and put the focus point over the first point and then move it to the second point, it then determines the aperture required to get that depth of field. this method would be easy with a fence post.
bottom line read the manual for your camera, and experiment, with a digital camera it cost you nothing but some of your time.

[millertime24 8]

Thanks. But like I said the manual was less than helpfull on this topic. And it wasnt just one fence post. I shot a whole line of them trying to keep as many of them in focus as possible. I have a Pentax K10D and Im uncertian if it has a depth of field mode (again book not so clear), but in manual mode with autofocus off I was able to get some nice pics of the fence line while using an fstop of 22-27.

Muff #5048

[dragon2 0]

Tip: usually you want to stay away from the really high f-stops, as the lens gets worse quality-wise at it's highest f-stop and a few stops before that. Of course in some cases you really need the depth of field these f-stops provide, but most lenses are at their best at somewhere in the middle of it's range, so generally speaking for a lens that can go from f2.8 to f16, it performs best at f8 or so.

ciel bleu,
Saskia

[millertime24 8]

Thanks for the tip. My lense goes from 3.8-34. So 27 is kinda mid range I guess, but I never knew that about using the upper end of the fstop range. Again thanks.

Muff #5048

[pilotdave 0]

Just to clarify dragon2's post. All lenses are going to end up with lower quality at really high f-stops (small apertures) because you're squeezing the light through a tiny hole, which tends to cause the light to spread out (diffraction). It's good to experiment and there might be times you need the whole image to be in focus, but don't forget that having parts of the picture out of focus tends to make for nicer pictures. I found myself dealing with apertures around f22+ the other day when I was taking pictures of helicopters in bright sun. I needed a really slow shutter speed to blur the rotor, but that meant my aperture had to be tiny. I don't have a filter to block light, so there was no choice. The pictures came out fine, but they are not quite as nice as they would have been if I was able to shoot at with a bigger aperture.

EDIT: The upper end of your lenses aperture range really doesn't matter. f/27 is really high (small) on any lens, whether it goes up to 27 or 34 or whatever. Anything above probably 19 is where you'll start to see diffraction.

Dave