Bokeh & Depth of Field

[Huck Finn]

Wide angle lenses have great depth of field. I'm curious . . . At what aperture do you find that your wide angle lenses begin to throw the background out of focus to the point that bokeh becomes an issue in composition?

 

[RML]

Usually at the wider apertures (those are the lowest numbers, right?) and with the subject nearby. So, with my CV 25/4 I'd get the most OOF when using f4 and the subject within 3 meters (preferably closer by). And using a high shutter speed helps as well.

 

[Pherdinand]

The trick is, wide angles can also be focused much much closer, usually. My 17mm goes down to 15 cm i think, while a 50mm goes to 40-50 cm on an SLR or just a bit less than 1m for the RF's. Thus, you do have shallow-DOF wide-angle pictures as well - just stick the lens in the nose of the subject.

 

[doubs43]

Re: Bokeh & Depth of Field

Wide angle lenses have great depth of field.

All lenses, at the same f-stop, will have exactly the same DOF when the subject is precisely the same size in the picture. WA lenses only appear to have greater DOF because objects are rendered smaller when the picture is taken from the same position as a longer lens.

Walker

 

[That Guy]

Then why does my 15mm indicate a DOF of 0.3 m to infinity at f11 when focused at 1 m and my 90mm indicates 0.9 to 1.1 meters when focused at the same distance?

 

[wlewisiii]

Same size in the picture. This is different than same distance from the lens, to put it mildly.

Google "hyperfocal distance" for more detail.

William

 

[doubs43]

Then why does my 15mm indicate a DOF of 0.3 m to infinity at f11 when focused at 1 m and my 90mm indicates 0.9 to 1.1 meters when focused at the same distance?

William is correct. The image must be the same size in the negative, not the same distance from the camera when the picture is taken.

Walker

 

[StuartR]

I think 35mm f/2 at close focus (1m) looks pretty good. Plenty of bokeh.

 

[RML]

I think 35mm f/2 at close focus (1m) looks pretty good. Plenty of bokeh.

Plenty of OOF, you mean. Bokeh has to do with the (subjective) quality of rendering of the OOF area.

 

[sfaust]

To help get more OOF backgrounds, you can also adjust focus so that your subject is at the very end of the in focus range. Ie, if you focus on your subject, and the depth of the area in focus is 30' deep, refocus closer so that your subject is at the very edge of the that range. That puts your range of focus from where to subject is standing to 30' in front of you, with very little behind your subject. Otherwise, you may find that if focused on your subject you may have 10' in front, and 20' behind your subject in focus. On SLR's, you can confirm this with depth of field preview and pretty much make the focus decision visually. With RF's you just have to calculate the DOF and adjust appropriately based on the lens scale. I usually also take a second exposure at close to normal focus as a safety shot because I sometimes pull the focus range too far forward and the subjects gets slightly soft.

 

[Huck Finn]

Thanks, Stephen. Sounds like reversing the hyperfocal distance.

Thanks, everyone, for your replies. I haven't been using wide angles on my rangefinder & when using them on my SLRs in the past OOF area was never really something I looked at on these lenses.

 

[sfaust]

Thanks, Stephen. Sounds like reversing the hyperfocal distance.

Exactly!

 

[That Guy]

Thanks for the pointers William and Walker. Did some Googling and some reading. Found a great calculator.

I've played on DOF for a long time but never really knew the math behind it. Or that there was math behind it. And the hyperfocal distance bit will be helpful with my Bessa-L. Thanks guys! 🙂