How do I use the focus distance/depth-of-field scale on a Pentax 50mm f/1.7 when shooting for bokeh?
Asked 10/11/2016
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I’m new to DSLRs and have a Pentax K-x with an SMC Pentax 50mm f/1.7. I’m confused by the distance and depth-of-field markings on the lens. If I want to shoot near wide open (around f/1.7–f/2.2) to get background blur/bokeh, should I be using the hyperfocal distance scale at all? Also, what does the red diamond indicate, and why does the depth-of-field scale only seem to show markings from about f/4 and smaller apertures?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
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The hyperfocal method is a way of insuring that everything in the background appears to be in focus in the final image as it is displayed. If you want your photo to demonstrate background bokeh then the last thing you want to do is shoot with the aperture set narrow enough that the subject distance is within the hyperfocal distance.
The concept of hyperfocal distance is based upon the illusion of depth of field. There is only one true focus distance. But things on either side of that distance appear to our eyes to be in focus when the blur they demonstrate is too small for our eyes to see it as blur. As the aperture is set to a more narrow setting the depth of field increases. When we have set the aperture so that the depth of field extends from the subject distance behind it to infinity we are using the hyperfocal distance. This is the opposite of blurring the background to get bokeh.
In order to get background bokeh you need to set the aperture wide enough (lower f-number) and use a subject distance short enough that the background is well behind the limits of the depth of field given by the choice of focal length and aperture (as well as display size and viewing distance which also affect the perceived depth of field).
For more on how to read and use the Depth of Field scales on older lenses, please see: What are "Depth of field and focus scales"?
Here are some more links to resources regarding the focus/depth of field scales on lenses:
https://photographylife.com/hyperfocal-distance-explained
http://www.fineart-photography.com/dofScale.html
http://www.lawrencephotographic.com/Articles/DOF%20Scale/dof_scale.htm
http://www.alanrossphotography.com/understanding-lenses-depth-of-field/
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
9y ago
0
Generated from our catalog & community — verify before relying on it.
For bokeh, you generally do not use hyperfocal distance. Hyperfocal focusing is meant to maximize apparent depth of field so that distant backgrounds look acceptably sharp. That’s the opposite of what you want when shooting at f/1.7–f/2.2 for blur.
On your lens, the red diamond is the main focus index: whatever distance lines up with it is the actual focus distance. The nearby red line is for infrared focus correction.
The paired f-number marks on either side of the index are the depth-of-field scale. As you focus, the distance scale moves against those marks to show the approximate near and far limits of acceptable sharpness for a given aperture. Lenses often omit wide-aperture markings like f/1.7 or f/2 because the depth of field is so shallow that it would be difficult to show usefully on the scale.
So if you want bokeh, simply choose a wide aperture and focus precisely on your subject. Don’t worry about hyperfocal distance in that case.
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