DOF Calculator question

OK - I've been studying that DOF Calculator link :

http://www.dofmaster.c​om/dofjs.html

I am still unclear on the Hyperfocal Distance and maybe someone could better explain this to me. I'll give you an example.

Say I'm shooting with my 28-135mm lens @ f/5.6 and I have a "group" shot of like 50 people (concert band) that is 100 feet away and spread out over the stage. The "group", let's say is 20 feet deep.

To effectively get everyone in the shot, I have to stand back in the auditorium say 150 feet away, so I have to zoom out to 35mm. So the figures I put into the DOF Calc is: 35mm, 5.6, 150 feet. The results are that everything from 120.1 feet in front of me stretching to Infinity will be in FOCUS. Right? Anything less than 120 feet will be out of focus, right?

OK, now what I don't understand is the Hyperfocal Distance figure - 37.5 feet. The "Focus at Subject Distance" says 150 feet. OK, fine. What does the 37.5 feet mean???

Getting closer, thanks again ...

The way I understand is that you could re-focus at a point 37.5 feet in front of you with those settings to get the maximum DOF. In other words it's letting you know that if you wanted to get your subjects in focus but include the max amount of the foreground in focus that is where you would focus. if you do not care about getting more foreground in focus then keep your focal point on the subjects.

The hyperfocal distance is the closest distance that you can focus at where infinity will be within your specified limit. If you focus at the hyperfocal distance, infinity will be at the far limit, and 1/2 the hyperfocal distance (about 19 feet in your example) will be at the near limit.

Caution: hyperfocal distance is calculated assuming that misfocus is the only cause of softness (not true, especially with digital cameras), and the standard "circle of confusion diameter limit" assumes that you're making prints no larger than 8x10 and using film and paper of a quality available before WW-II. Focusing at the hyperfocal distance calculated with the standard CoCDL will generally render objects at infinity as being noticeably soft.

Thanks guys... It'll sink in some day, I hope...

The hyperfocal distance is, as stated above, the closest distace at which you can focus where infinity will fall within the acceptable DoF range. When focused at the hyperfocal distance, the close limit of the acceptable DoF will be approximately one-half the hyperfocal distance (actually one-half the hyperfocal distance less one focal length).

Knowing the hyperfocal distance is useful for several purposes, such as tracking moving objects in the near distance without constantly refocusing, or taking quick pictures without having to focus first.

This latter use, taking quick pictures, is the concept behind "fixed-focus" point and shoot cameras. If you were designing a camera for general use, where the camera has a fixed-aperture, fixed-focus lens (à la the old Kodak Brownie), you would set the focus point of the lens at the hyperfocal distance to make the camera as general-purpose as possible.

In the old days before autofocus, many photographers would keep their SLRs set to f/8 and the focus set to the hyperfocal distance, with the shutter speed set for the proper exposure with the film being used. This was called "Brownie-ing" the camera. The camera was then ready to take an instant picture upon demand.

Many famous photographs were taken this way. Such pictures were rarely photographically perfect, but many won their takers much money and/or fame, such as the image of the flaming passenger jet nose-diving at full power into the North Park area of San Diego.

This technique was so common that most lenses had the DoF for various apertures right on the lens. Setting the lens at the hyperfocal distance was a no-brainer requiring zero calculations.

In today's photographic environment, this technique is not nearly so useful for several reasons.

First, autofocus has improved to the point where it is almost instantaneous with a good camera and a good lens. This makes it unnecessary to preset a camera in order to obtain good virtually instantaneous pictures.

Second, the proliferation of zoom lenses has rendered hyperfocal distances difficult to calculate in the field. For a given aperture, a zoom lens has an infinite number of hyperfocal distance between the minimum and maximum foxal lengths.

And third, even good prime lenses typically no longer have DoF scales, requiring in-field calculations (or good memorization).

Hyperfocal shooting has become somewhat of a lost art for general photography.

So let me ask 1 more - hopefully not stupid - question. How does AutoFocus play into all of this? I mean, if I have all of my AF Points selected and am pointing into the middle of my group shot. Do I need to go to Manual Focus to deal with these figures we've been discussing? Or if I'm that 150 feet away and just let AF focus for me, shold I expect to get everyone in focus?? Sorry...

Basically, hyperfocal focusing is a manual thing. Autofocus kind of defeats hyperfocal focusing.

I should add one more thing to my list of reasons why hyperfocal shooting is not a popular or convenient with modern equipment:

Fourth, most modern lenses have very generalized distance scales compared to older lenses. This lack of accurate distance information on the lens makes setting to a given hyperfocal distance very difficult.

For example, the Canon EF 28-135mm f/3.5-5.6 IS USM lens has a distance scale that, in feet, reads 4, 7, 15, 50, inf, with no graduations or tick marks. With a scale like that, how is one to set a hyperfocal distance of 216 ft (f/8 at 100mm on a 20D)?

As for getting everyone in focus in a group shot, if you use an aperture such that your DoF is not super shallow, say between f/8 and f/16, and let AF lock on someone close to the middle of the group, you should have no trouble.

Unless, of course, your group is an Army division in parade formation.

Even then, you can assure good focus on a large group by placing enough distance between yourself and the closest members of the group, even if that means cropping the picture in post processing.

Thanks Roger ... yea, that "between f/8 & f/16" thing is where I had originally been thinking ... In another thread, I asked a similar question about my upcoming group shot, and was told f/5.6 would "be fine" at a distance of 100 or so feet away ....(edit: This will be indoors with only stage lighting.) Hence my embarking down this path of really trying to understand DoF, Focal Distance, and hyperfocal distance... Originally, I thought the recommended f/5.6 would just create too little DoF and result in out-of-focus people in the group. of course the larger f/5.6 aperture would allow more light than f/16 .... I think what I'll do is capture a series for comparison, just as a test. (I do this on next Monday night.)

In photography, there are three words to help one get a good shot:

Bracket, bracket, bracket.

Were I doing the shoot and had access to the area, I would set up some markers (chairs would work) defining the approximate center and left, right, front, and back extremes of the group. I could then play with apertures to find the best that would allow all markers to be in focus under real shooting conditions.

Then I would still bracket the group.

Cody21 wrote in post #5522384
OK, now what I don't understand is the Hyperfocal Distance figure - 37.5 feet. The "Focus at Subject Distance" says 150 feet. OK, fine. What does the 37.5 feet mean???

Think of the 37.5 feet as nothing to do with your other depth of field calculations. Ignore it, except to acknowledge that if you wanted the greatest depth of field for 35mm and f/5.6 you would focus at 37.5 feet.

For every aperture and focal length there is a hyperfocal distance. That distance is where you get the greatest depth of field for your chosen aperture and focal length.

Now, because you are only concerned with finding enough depth of field at your known subject distance and not the maximum depth of field, you aren't necessarily going to be wanting to use the hyperfocal distance. If you did focus at 37.5 feet your subjects should be in focus though, subject to the other points raised.

Mike

You shouldn't need to be 150' away to get 20' DOF. The Hyperfocal Distance figure means that, if you have 4 rows of people, you can probably focus on the 2nd row & pull all the rows into focus.