Fixed focus lenses and apertures

[CliveC]

How do different apertures affect the depth of field in fixed focus lenses such as those on the Olympus XA1 or the Olympus Pen EE? Those cameras have a minimum focus point of 1.5m but focuses from there to infinity.

 

[ruby.monkey]

Same as for any other lens -> the smaller the aperture, the greater the depth of field. Plug your focal length and aperture into a DoF calculator and away you go.

 

[CliveC]

Same as for any other lens -> the smaller the aperture, the greater the depth of field. Plug your focal length and aperture into a DoF calculator and away you go.

Okay, let's say I take a picture at night of a person 2 meters away in front of scenery at f/3.5. What's in focus?

With a traditional lens, I can set either the person or the background to be in focus. What happens to fixed focus lenses?

 

[Landshark]

See post #2

http://dofmaster.com will have your answer.

The formula doesn't change whether it's Fixed focus or not.

 

[CliveC]

I guess I'm still a little confused.
I plugged in values for my XA1 and it spits out a hyperfocal distance of 33.6 feet (10.2 meters) at wide open f/4. I take that to mean that anything between half that (16.8 feet, 5.1 meters) and infinity will be reasonably sharp, but that still further than the minimum focus distance of 1.5m (or about 5 feet) as stated by Olympus.

It's not until f/13 or so until the hyperfocal distance reaches the 3m, putting the depth of field at 1.5 m to infinity.

As such, if it's shot wide open, the close focus distance is not 1.5 meters, but 5 meters? Or Olympus just saying that objects at 1.5 meters look in focus enough to pass muster and that the camera will likely not be shot much at f/4?

 

[tunalegs]

I guess I'm still a little confused.
I plugged in values for my XA1 and it spits out a hyperfocal distance of 33.6 feet (10.2 meters) at wide open f/4. I take that to mean that anything between half that (16.8 feet, 5.1 meters) and infinity will be reasonably sharp, but that still further than the minimum focus distance of 1.5m (or about 5 feet) as stated by Olympus.

It's not until f/13 or so until the hyperfocal distance reaches the 3m, putting the depth of field at 1.5 m to infinity.

As such, if it's shot wide open, the close focus distance is not 1.5 meters, but 5 meters? Or Olympus just saying that objects at 1.5 meters look in focus enough to pass muster and that the camera will likely not be shot much at f/4?

I doubt they have the focus set so that infinity is in focus wide open. Contrary to popular belief few fixed focus cameras actually have the focus set to the hyperfocal distance (this is especially true on old box cameras and the like with long lenses and medium formats).

A lot of box cameras for instance will make anything beyond 50' or so somewhat soft despite the small apertures used. I would imagine for a 35mm camera the focus is probably fixed around 10'. Which with the 35mm lens means one could expect everything from about 7' to 14' to be in focus wide open. You'd only get infinity at f16, and "close enough" to infinity at f11.

 

[Denverdad]

Although I don't have this camera, I was curious enough to see if I could find some answers. The best thing I found was this site which discusses the XA1's depth of field and gives a pretty good explanation I think. As you can see from the specifications the minimum aperture of the XA1 is apparently f/22, and it must be at that aperture that the DOF is calculated.

I play around a bit with old fixed focus medium format cameras myself, and find that some of them are also capable of producing surprisingly sharp images given the simple design. It comes down to using small apertures on short focal lengths. The caveat is that it only works if there is enough light! So I agree with recommendations for using higher speed film with this type of camera.