DOF discussion

[forestgnome]

utterly basic...yes...but it's me

I'm keeping a small notepad in my camera case now to avoid repeated mistakes, and I need notes on the basics of focusing on a field with extreme depth.

1) How do you know if f/16 is small enough, or if f/32 is smaller than neccessary?

2) How do you focus when there is foreground subject matter right in front of you and a peak 3 miles away, and nothing but air in between?

3) Admittedly, I always forget about the DOF Preview button. Is this really a reliable tool? Can you determine acurately your DOF this way?

Thanks for any help

 

[Grumpy]

1) How do you know if f/16 is small enough, or if f/32 is smaller than neccessary?

Experience will tell. You certainly are on the right track by keeping notes.

2) How do you focus when there is foreground subject matter right in front of you and a peak 3 miles away, and nothing but air in between?

Use a small small f/stop, and focus at the hyperfocal distance for that lens and f/stop combination.

Hyperfocal distance (HD) is defined as the distance from the camera to the nearest point in the scene that is in acceptable focus when the lens is focused at infinity at any given f/stop.

By focusing at HD, depth of field will extend from halfway to the point of focus in the scene to infinity. It is the greatest DOF that can be achieved at a given f/stop.

3) Admittedly, I always forget about the DOF Preview button. Is this really a reliable tool? Can you determine acurately your DOF this way?

I’ve never found it especially useful. Usually, the viewfinder darkens so much the image becomes quite difficult for me to see. Also, viewfinder images are small enough that they always seem to have more DOF than they will when the image is enlarged to normal viewing size.

G.

 

[Brambor]

some large format lenses are great at F32 but the SLR lenses that I use are not. F16 is my max and even with that I try to go lower.

Two objects - focus 1/3 to 1/2 between the two and go f16 (cringe)
(in digital age - chimp the lcd and double check that you achieved the focus and adjust as necessary)


DOF - It never worked for me yet some people swear by it. I would love to meet someone and personally have them show me. I don't get it visually.

 

[DougPaul]

I'm keeping a small notepad in my camera case now to avoid repeated mistakes, and I need notes on the basics of focusing on a field with extreme depth.

Don't forget that the camera automatically records many of the settings in the EXIF. (One good tool for accessing them is http://owl.phy.queensu.ca/~phil/exiftool/. Free.)

1) How do you know if f/16 is small enough, or if f/32 is smaller than neccessary?

When you start using very small apertures, diffraction blurring becomes a factor. I'd guess that one should start thinking about it for anything smaller than F/16.

3) Admittedly, I always forget about the DOF Preview button. Is this really a reliable tool? Can you determine acurately your DOF this way?

IMO, it is very hard to judge the DOF accurately through a viewfinder or a camera LCD display. You could just take several shots bracketing the F-stop and select the best later.

You could also use a P&S for the picture. The smaller sensor requires a (physically) smaller lens, so for the same pic (ie same F/stop and eFL) it will have a larger DOF.

Another approach would be to use a tilt-shift lens: http://www.luminous-landscape.com/tutorials/focusing-ts.shtml.
An extreme example:
http://www.luminous-landscape.com/1photo-pages/y/yellow.shtml
(from http://www.luminous-landscape.com/locations/monument.shtml)


A tutorial on DOF: http://www.luminous-landscape.com/tutorials/understanding-series/dof.shtml

Doug