Jump to content

Hyperfocal distance with EF lenses


frank_gross

Recommended Posts

<p>It seems to me that if you are using a DOF calculator AND manually focusing, rather than auto focusing, you would merely find an object approximately the hyperfocal distance from the camera, focus on it, then recompose (but don't refocus) your picture and shoot.</p>
Link to comment
Share on other sites

<p>I just guesstimate with my Nikon V1 and dSLR. Unfortunately the V1 doesn't retain manual focus settings after the camera is turned off so I have to reset my zone focus every time. It's pretty easy since the V1 has a smallish CX (1-inch) sensor. I autofocus on any subject at the desired distance, then switch to manual focus. Done.</p>

<p>Same with my dSLR (APS-C sensor) - I just guesstimate a distance appropriate for the focal length and aperture I'm using, mostly for available dark situations - there aren't many situations where either camera hunts around in AF mode, but zone focusing removes any slight delay.</p>

<p>Keep in mind that zone focusing and hyperfocal settings are compromises. If you pixel peep you'll see the actual zone of sharp focus is fairly shallow. And if you stop down enough for deep DOF, you're into diffraction. It's a compromise, but if you can accept it for what it is, the technique can be useful for some situations.</p>

Link to comment
Share on other sites

<p>Yes, i understand the advantages of using it in some situations hence my specific question.<br>

Keeping in mind the "not sharp as a knife" results and the importance of coc for 'optimum' quality it doesn't serve me well to 'guestimate' or 'estimate' or hope to find an object at 'approximately' the HFD in the scene. I want to know how to pre-set my canon auto ef lenses without a proper distance scale to manually focus them</p>

Link to comment
Share on other sites

<p>If you don't want to estimate distances (which is really pretty easy once you train your eye - every Boy Scout learns this trick during his 1st year) or have difficulty doing so, you could carry around an old 1950s rangefinder (they're about twice as thick as a fountain pen and about 6-7 inches long) in your pocket or camera bag (some even fit in the camera's hot shoe). You could either set your hyperfocal distance on its distance scale, scan your scene until you found something at that distance, and then focus your camera on that object, or do the reverse, similar to what I suggested above - except that you don't have to estimate a distance, you actually measure it with your rangefinder, focus your lens on the object you measured. </p>
Link to comment
Share on other sites

<p>More sophisticated rangefinders are available now - they're used in construction, surveying, sports, hunting. I used to use 'em for safety inspections on construction sites, to estimate heights based on triangulation. Search for golfer's laser rangefinders for a start. Those are better than the old Rowi accessory shoe rangefinder I have in my camera bag but seldom use.</p>
Link to comment
Share on other sites

<p>Zone focussing isn't really an exact science, it depends on the focal length of your lens and how much light. It works best on a wide-ish angle lens that you can close down a bit to get a wide DOF. I guess on the new digital lenses, you pre-choose by focusing in manual on a spot at a distance you think your average picture will be taken from and go and shoot, keeping your focus zone in mind. If you see something that you think will be outside, you can refocus manually. Really its a guesstimate and really you take a few and hope you get the hang of it. Pretty much what Stephen said, only you have to have a rough idea of what the zone is and you have to stay in it. </p>
Link to comment
Share on other sites

<p>They work by triangulation, just like a rangefinder does in rangefinder cameras. Turning the wheel either adjusts a mirror or prism until you have images coinciding. When you have coinciding images, you can then read off the distance on the scale.</p>
Link to comment
Share on other sites

<p>It’s perhaps important to remember what depth of field is: the range of distances over which the final image appears sharp. Inherent in standard values for the circle of confusion are assumptions about enlargement and viewing conditions; if what is assumed differs from the actual (e.g., pixel peeping), the image may not appear sharp. Diffraction, while a real and unavoidable phenomenon, is an overrated problem in most cases. Except, of course, for pixel peepers.</p>

<p>Setting the hyperfocal distance is simply a special case of zone focusing in which the far limit of DoF is at infinity. Canon once had a very simple solution for the general case: “Depth of Field” AE, which would set the focus and <em>f-</em>number given a near and far distance. It was a bit optimistic on the <em>f-</em>number, but seemed to do as good a job on focus as I ever was able to do with real distance and DoF scales (i.e., large enough to be readable to reasonable precision). But the feature seems to have vanished for good after the EOS-1Ds. I’m not including the A-DEP feature on some of the lower-end bodies because it didn’t allow the user to select the near and far points.</p>

<p>With a smartphone app (or at least a programmable scientific calculator), it’s simple enough to calculate the focus and <em>f-</em>number. What’s tough—at least for me—is setting the focus. I don’t trust my estimates of distance, and I really have trouble setting any distance with microscopic distance scales.</p>

<p>The only practical way to systematically employ zone focusing with EF lenses (or any AF lenses I’m aware of) is probably to find an object at the desired focus distance—either harmonic mean or hyperfocal—and focusing on something at that distance using the camera’s AF. For someone who’s much better than I am at estimating distances optically, the procedure is simple. For others, some type of rangefinder—optical or laser—might be needed for reasonable accuracy. For zone focusing between two distances, the near and far distances could be measured with the rangefinder, and an object at the calculated distance could then be found, and the camera could be focused on that object. I’ve thought about this for years, but never have gotten around to trying it ... And it’s obviously a bit tedious for most street work.</p>

 

Link to comment
Share on other sites

<p>It doesn't make any sense to find the perfect hyper focal length, (greatest zone of circles of confusion) if you want to "zone focus" unless for some bizarre reason you are going to adjust the hyper focal length for every photo you take. Yes, can pick a general distance you want to shoot at and figure out the hf length for that, and then you just want to leave it. But really the overall DOF changes as you reset the aperture anyways. All you need to do in real practice is just set the distance you plan to include in your DOF. For instance, St. HCB used to set his 50 at around 10'. He got to know by experience what 10 feet was and he therefore just would set exposure point and shoot. If you use a 35 or 28 or wider, you can set your focal distance at about 10 feet or less and on a sunny day, close the aperture down to f8 or more and you will have a nice wide range of "acceptable focus" which is what zone focusing is about. You know that anything after so many feet to about so many feet (sometimes depending on light and the lens infinity) and just make sure what you want in focus is in that zone. You then will have to decide what "acceptable" focus is. Its not difficult and over thinking it won't make it any easier. Just go out and try it.</p>
Link to comment
Share on other sites

<p>Barry,</p>

<p>I oversimplified things a bit in equating zone focusing with setting the hyperfocal distance. For a fixed camera position and framing (i.e., lens choice), there usually are three parameters to play with: near and far DoF limits, and <em>f</em>-number. Choose two and the remaining parameter is fixed. With zone focusing, you choose the limits and the <em>f</em>-number is determined. This doesn’t always work: when great DoF is needed, the required <em>f</em>-number may be greater than can be set, or may be too great for other reasons (e.g., diffraction or motion blur). Another approach then is to choose the greatest acceptable <em>f</em>-number and one of the limits, and let the other limit fall where it may. Setting the hyperfocal distance chooses the aperture and far limit (infinity), and lets the near limit be as it may. A variation is to work out a compromise among both limits and the <em>f</em>-number.</p>

<p>If you always use the same <em>f</em>-number, the hyperfocal distance doesn’t change. Similarly, the focus distance for a far limit that doesn’t extend to infinity remains the same, as HCB well knew.</p>

<p>Whether changing the focus for every photograph is “bizarre” depends on what you’re doing. As I indicated, this usually is pretty cumbersome for street work—if you mess with this stuff, you often miss the shot. But matching the focus distance to the scene is often standard practice for landscape, architecture, or product photography. I did this for years with MF lenses, and Canon’s DEP mode did essentially the same job much faster with EF lenses. Without DEP, it’s much harder than with either previous method.</p>

<p>HCB had manual-focus lenses with readable distance and DoF scales, so setting a given distance was fairly simple, as was fine tuning to adapt to slightly different conditions—all quickly worked out by glancing at the distance and DoF scales. At least for me, this isn’t true for most AF lenses, which have small distance scales and very small DoF scales. Mentally interpolating from a nonlinear distance scale was always a bit of a challenge, and it’s much tougher with a small scale with fewer marked distances. With my TS-E 24 mm <em>f</em>/3.5 (the original), I can easily choose <em>f</em>/8 and set focus to 1.5 m to have the DoF between just under 1 m and just over 3 m. On my 35 mm <em>f</em>2, <em>f</em>/8 isn’t even marked, so I need to interpolate on both the distance and DoF scales. I can usually get the focus within the ballpark, but can’t get nearly the precision that I get with the 24 (this has been fixed with the TS-E 24 mm Mk II, which has much smaller scales). But perhaps I’m carrying landscape assumptions and habits into an arena where they’re less important.</p>

<p>Calculating the focus distance using whatever method is fairly simple, but the same is not always true for setting that distance. I had thought this difficulty was the essence of Frank’s original statement “when there is no proper distance scale to manually set the focus.” To be honest, his question remains an open one for me as well. The last two decades have seen tremendous advances in photographic tools, but perversely, getting the desired DoF isn’t nearly as easy as it was before AF. I’ve always found this mind boggling ...</p>

Link to comment
Share on other sites

<p>Harrold Merklinger wrote a series of four articles, entitled "Adjusting Depth of Field", for Shutterbug mag in the early 90s. In these articles he does cover hyperfocal distance. You can find them here:</p>

<p>http://www.trenholm.org/hmmerk/HMArtls.html</p>

<p>If you are into mathematics (then I do not stand amongst you ;~), you might enjoy Merklinger's "The INs and OUTs of Focus"</p>

<p>http://www.trenholm.org/hmmerk/TIAOOFe.pdf</p>

<p>Personally, I find it too much of a kludge to use hyperfocal calculation/tables to focus an EF lens, to obtain the deepest DoF. I have better luck auto-focusing (with spot focus) on the object that I want to be in clearest focus, then I stop down as far as my camera/lens combo will allow ~ while still yielding good results (derived by real world experience, AKA, shooting the same scene at several apertures and selecting the best result from those).</p>

<p>Cheers! Jay</p>

Link to comment
Share on other sites

<p>Thanks Jeff for the explanation. What I'm focussing on (no pun intended:) is for most street and documentary work, where you do want to shoot quickly if you are shooting a certain style of candid basically. And so you want to know most importantly the close and far range of "acceptable" focus. Hyperfocal length is good to know, but basically you want to know for the distance set on your lens, what the basic DOF is going to be. That way you can hold your setting (given the parameter of necessary shutter speed/aperture mix where you want to maintain a wide DOF. All on rule of thumb and approximations as are reading the DOF markings on a Leica or other camera. Not precise, nor is precision needed. Of course it starts to break down on longer lenses and in lower light where the DOF range narrows. On re-thought, using HCB as an example for zone focusing is probably not completely accurate. I think what he did was just set focus at 10 feet or so and then just learned through experience to get to "feel" that 10 feet, and thus only had to compose and fire, not focus. Though some of his so called famous photos are not by any means what we today would call sharp. Zone focusing is more like the old Kodak's and family cameras that had a portrait setting, a group setting and a "landscape" setting, I think you can do this on digital everything dslr's if you can set in manual with a wider angle lens on a day with plenty of light. You can zone by manually focusing on something approximately at the working distance you want, and depend on a wide DOF to carry the load. should work.</p>
Link to comment
Share on other sites

<p>Barry,</p>

<p>Full disclosure: though I’m fairly adept at DoF calculations, I only use them to ascertain general principles. I’ve never done a DoF calculation in the field—it’s just too much trouble. And in most street photography, there just isn’t time. Most of the time, I just pick an aperture, focus on the subject, and take the picture—often even with landscapes.</p>

<p>I agree with your implication that hyperfocal distance isn’t always that useful for street photography—if for no other reason than that in many cases, there is no need for the DoF to extend to infinity.</p>

<p>I’m not sure I agree that a guesstimate of near and far limits is as good as can be achieved using zone focusing with an MF lens, though. But perhaps that’s just me. I never was that good at estimating distances, so more often than not, I used the camera as a rangefinder to get the distances, and then set focus accordingly. This works fine for street work as long as you can do it before you need to make a quick shot.</p>

<p>The same could be done with Canon’s DEP mode by using DEP mode to set the focus and then changing to another mode (Av, M, P, or Tv) and waiting for the appropriate shots. With different framing, of course, the process needs to be repeated. This all assumes, of course, that AF has been taken off the shutter release.</p>

<p>The only difficulty in duplicating zone focusing or “idiot” settings on most AF lenses is that the distance and DoF scales are so small that they’re mighty hard to read. So I still see it as something that was much easier to do with a $150 Pentax K1000 than it is with a multi-thousand-dollar digital wonder. For me, anyway.</p>

<p>A comment on Merklinger: <em>The INs and OUTs of Focus</em> (Jay’s second link) may be interesting reading even if you ignore the math. Merklinger’s basic premise is a bit different: rather than trying to achieve maximum apparent sharpness in the print, he tries to achieve maximum recognizability of objects in a scene. Of course, some distant objects must be viewed at great magnification even to be recognized as objects— one of his examples showing his sister-in-law is at 160× enlargement. He gives several formulas that can be rearranged to give focus and <em>f</em>-number, but in most cases, he simply focuses at infinity, and accepts some loss of sharpness in near objects. If your street work involves surveillance, recognizability may be just what is what is wanted. I’ve never felt the need to make such enlargements, and I usually want near objects sharp, so I’ve not found Merklinger’s approach applicable to general photography. But this approach could have done wonders for David Hemmings had it been available in 1966 ...</p>

<p>Merklinger’s approach does have one advantage, though. If you take the standard approach and for some reason decide to view an image at greater overall magnification than covered by the standard assumptions, the sharpness in distant objects quickly becomes apparent; with Merklinger’s approach, this is much less an issue. Of course, infinity may not be the best choice for most street work. But the general concept can still be applied by focusing slightly farther away than you normally would. As with the conventional approach, this is amenable to all manner of calculations—but practically, it’s probably just a matter of “prefocusing” on something slightly beyond where you expect the subject to be. As I said, though, I hardly ever use this approach, so I don’t really speak from experience.</p>

Link to comment
Share on other sites

<p>Jeff, I actually seldom use zone focusing, I prefer A priority and focus in the street. But I do use it lets say, when using a 35mm or a 21mm on a sunny day. Lets take the easier example of the 21 on a sunny day, where I can set the aperture at f8 even on aperture priority and set focus at 7 feet and know that pretty much anything I want to shoot that is 4 or 5 feet to almost infinity will be in "acceptable" focus. You pretty much can't go wrong for fast shooting. On the 35, I'd be a little more careful. As far as a guesstimate, most lenses, at least of the variety I use, have DOF marks on them. And then, of course if you are using one of many DSLRs, there will be a DOF button or lever that stops the lens down so you can see the area of focus through the viewfinder. I know that new digital lenses without aperture rings etc., are more of a challenge, but again, with a wide angle lens and also checking with the DOF button. If there's enough light out, I think one should be able to do it. I'll try it on my D700 and see what I get and report back. </p>
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...