Depth of Field - hypefocal

[aqualarue]

Just to qualify this has nothing to do with the one third in front and infinity behind Depth of field which is what we all learn as babes in the

photographic world.

 

Just a quickie please: When shooting for max D.o.F using hypefocal charts where the idea is to get half the distance in focus that is in front of

the subject, do you focus manually? or can you still use the focal points (when you select only one focal point to use that is) from the

camera's automatic focus? I only have electronic settings on my film camera (canon 300v) and also a digital camera. So i have no rings on

the front. I know of course that you can focus manually on the digital camera and the film camera, but all the websites use manual aperture

and focus examples to explain, and this is confusing because I have no idea what they mean. As I understand it when you focus manually on

say an object 6 feet away and everything alse looks blur then you should ignore this and trust the chart calculations when adopting this

approach.

 

thankyou

 

Chris.

[anisshah]

<can you still use the focal points ... from the camera's automatic focus? ... film camera (canon 300v)>

 

Try A-DEP mode.

[jpo3136b]

Hyperfocal is the distance where everything from the near side of depth of field to infinity is in focus. Since depth of field varies with

aperture, hyperfocal will be farther away from the photographer at wider apertures. Hyperfocal distance will also vary from one focal

length lens assembly to another.

 

Yes, I focus manually. There is a chart on my lens barrel. I imagine the charts you are using imitate the calculations on these depth of

field range markings on a lens barrel. In the attached picture the chart I use is a depth-of-field scale that is the middle set of markings in

the picture. The hyperfocal in this example picture would be at about 100' for a shot at f/32. The point of focus would fall at 150'.

 

Asking about how to focus on the correct point: manual would be easiest if you know the distance. If there are no markings on your

barrel, you will have to either estimate or measure somehow else. By hook or crook, doesn't matter what system you use, the lens

must be set at the correct point of focus for that aperture in order to keep everything to infinity in focus.

 

". . .and everything alse looks blur then you should ignore this and trust the chart calculations. . ." The short answer to this is, Yes.

Some cameras come with a depth-of-field preview lever. If this lever is absent, then it is not likely that the photographer will see with his

eyes the depth of field that would be recorded by the camera.

 

I noticed that you said you were confused by other examples on websites. As you can see by the picture, I would use the markings on

the lens barrel to determine, in this case, that I would want to focus no closer than 150' away in order to achieve clarity to infinity. I

hope this photo helps you to relate to how people would calculate this using a manual lens assembly.<div></div>

[jpo3136b]

The more I think about this, the more I think you might be in quite a predicament. When you say there are no rings on

the lens; that you only have electronic settings: Do you mean there is no distance scale on the lens of your camera?

 

If so, then I imagine your only recourse would be to find some software function that would let you drive the robot in the

lens to focus at a prescribed distance. If you have no way of knowing at what distance your camera is focused, then the

pursuit of this hyperfocal will be fruitless. You have to be able to set your point of focus at the right spot in order to do

this knowingly.

 

Now, if there is no scale on the camera, then the only thing to do would be to calculate the point of focus for the

hyperfocal at a given aperture; and then, somehow, measure on the ground to a landmark at that point. Then, focus on

that landmark. Such an estimation system might achieve hyperfocal with no in-camera measurements. It would be

rough, but it might work.

 

I have to say, though, that if you are this interested in focusing distances; I would try to step up to a camera with a more user friendly lens

assembly. If you had an all-manual lens, this whole question could have been answered at a glance. J.

[jpo3136b]

". . . half the distance in front of the subject. . ." BTW: this part of "half the distance" would be influenced by the focal

length of the lens. For example, if we had used a 35mm wide angle lens, instead of a 300mm, then the in-focus area

would be much larger.

 

So, the "half the distance" part would be relative to the distance from camera to subject and the focal length of the lens

assembly used. In the picture above, the subject would have to be 200' away if we were adamant about "half the distance" in focus,

because everything closer than 100' would be out of focus.

 

Let's say our subject is closer than 200' away. Let's say the subject was in the same room. Could we set point of focus

so that hyperfocal would be reasonably close to us, almost coincidental to "half the distance", by choosing a lens with a

wider viewing angle and shorter focal length? Would we be more likely to get a reasonable "half the distance" to subject

with a wide angle lens? Yes.

 

In the attached photos, we can see the 300mm lens, as above, next to a wider angle lens, Pentax 645 35mm. They are both set to have a

hyperfocal that will keep everything to infinity in focus at their narrowest apertures.

 

In the close-up of the 35mm lens, we can see that at f/22 (narrowest), with a point of focus just under 5 feet, hyperfocal

will fall at about 2.5 to 3' away. In the case of the wider-angle lens assembly, we would be much more likely to

encounter a common subject at 5 feet; so, we would be able to have everything from "half the distance" to subject all the

way out to infinity in focus with a wide angle lens at f/22.

 

I hope this has helped you some. Good luck. J.<div></div>

[jpo3136b]

And the closeup of the 35mm illustrating the closer hyperfocal to support a more reasonable distance to subject by

choosing a shorter focal length lens assembly.<div></div>

[anisshah]

<"When shooting for max D.o.F using hypefocal charts where the idea is to get half the distance in focus that is in front of the subject, do you focus manually?">

 

Just had a look at your previous thread on this subject. If your lens has no distance markings (e.g., the 18-55 kit lens), you might as well use autofocus, try to estimate subject distance, and use the corresponding settings from your chart. If your subject is roughly 6 feet away and you dial in f8, zoom out to 18mm and focus on the subject, everthing from around 3 feet to 75 feet should be relatively sharp.

[anisshah]

And on your film SLR, 28mm@f11 has a similar hyperfocal distance (6-7 feet) with 'acceptable' depth of field from around 3 feet to 35 feet.

[William Michael]

I am a little confused by a couple of phrases in your question.

 

But in a precision situation if I had to make my POINT OF FOCUS exactly 6ft from the camera`s film plane (or sensor plane) I would:

 

1. Set the camera on a tripod.

 

2. Drop a plum bob from the Line of the Film Plane (usually marked on the camera by a straight line through a circle).

 

3. Mark that point on the ground.

 

3. Measure 6ft along the ground - along the lens`s axis.

 

4. Set a vertical stick at that 6ft marker to camera height (usually another tripod)

 

5. Manually focus with my lens on that 6ft distance marker – at the height of the camera.

 

The lens is now focused at six feet, no matter what markings – or not - are on the ``rings``.

 

You can do the same, measuring backwards, from a vertical wall, provided you keep the camera (and lens) perpendicular to the wall. In this case you would not need a second tripod or vertical stake in the ground.

 

WW<div></div>

[aqualarue]

thankyou for your answers. I will have to find somebody who can explain to me how people arrive at these figues on lens

barrels, I have never used them and looking at the photos only confuses me becaus eI do not understand how they are

physically turned and how these decisions are made. I have only used the electronic readings that you get in the camera's

lens viewer. I use fully manual aperature and shutter speed settings all the time, and have always focuse with one af point.

I understand all the theory of hyperfocal but need to see a fully manual camera first, and to see how someone uses that.

 

By way of an example: I would assume that essentially (film C.o.C 0.03) focal length at 50mm subject distance 13 feet, I

would then have to set Av to f22, then electronically focus one single af point at around 13 feet, this would then guarrantee

me a depth of field distance from 7 feet to infinity? Am i correct? (figures as I see on my chart from the software that I

downloaded from Depth of Field master.com)

 

Thank for your help guys

 

Kind regards

 

Chris

[anisshah]

<" Am i correct?">

 

Yes, but you'll lose some sharpness at f22 because of diffraction. A wide-angle lens (28mm or even 35mm) would give you similar DOF at a larger aperture (i.e., before diffraction effects become significant).

[arjun_mehra]

<p>Chris, say your subject is eight feet away from you (technically, from your lens's focal center), and you want everything in focus from four feet away to as far back as you can get. To accomplish this, you'll have to refer to a depth-of-field calculation chart (or, to just visit a Web site that allows you to make the computation by providing a few figures) and focus on whichever point will make the near-end of depth-of-field four feet. It seems you know this, but, the narrower your aperture, the farther back you'll be able to render sharp (again, we're assuming you're fixing the near-end at four feet); as well, the smaller your focal plane and the shorter your lens's focal-length, the father back you'll be able to go.</p>

[aqualarue]

<p>Yes, thankyou.  It's pretty much sunk in now.  It was just that I kept coming accross information that indicated you should manually focus on that specific point rather than allow the camera.  But if I focus using only one AF point at the distance indicated by the chart tis should turn out to be more accurate than relying on my own eyesight with manually focusing.</p>

<p>Chris</p>

[arjun_mehra]

<p>Yes, it would work either way (though, as you say, trying to judge how far an object is, just by looking, can be difficult and unreliable — the closer it is, the harder the task becomes).</p>

[jgredline]

<p>John, Thank you so very much! This answered my remaining questions :)</p>