Tuesday, 27 July 2010

[HYPERFOCAL MODE]

I'm about to discuss a pet digital photographic peeve of mine, but I'll try to avoid turning [RANT MODE] up to [HIGH].

Back in the days when I used film cameras, I would make extensive use of the hyperfocal distance, particularly in my landscape photography. Don't be put off by the name: it's perfectly legal (as Eric Morecambe used to say, "They can't touch you for it!"). It's a simple but very effective idea, which exploits a basic optical property of any lens, which is:

For any given combination of focal length and aperture, there is a distance -- the hyperfocal distance -- which, if the lens is focussed at that distance, has the unique property that everything from half that distance to infinity will then be in acceptably sharp focus.

Useful, no? For example, the old "standard" lens for 35mm cameras had a focal length of 50mm. At f/16, the hyperfocal distance for that focal length is about 21 feet. Set the lens to f/16, focus it at 21 feet, and everything from 10.5 feet to infinity will be in acceptably sharp focus. Guaranteed! No need to focus on anything in particular.

To make this easy, lens barrels used to be engraved with "depth of field" marks, so that if, for example, you had a 50mm lens on the camera and were using an aperture of f/16, you would simply line up the "infinity" marking on the focus scale with the "f/16" marking on the "far away" side of the DOF scale. Et voilĂ ! Hyperfocal distance set!

Naturally, there is some pedantic quibbling about that phrase "acceptably sharp". This involves the positively theological concept of an "acceptable circle of confusion", and there are some lovely equations you can do which will deliver different hyperfocal distances depending on the value you supply for the circle of confusion, but this kind of focussing is always going to be an approximate business, and anyone seriously troubled by the size of their circles of confusion needs to start that search for a Life right away.

But that was then, and this is now.


Hyperfocal-ish... Don't know about infinity, but both
the near and the far fences are acceptably sharp


Digital cameras are amazing things. The sheer brilliance of the programming that underlies their functionality is mind-blowing. I used to be a "manual only" kind of guy. I'd meter off the ground at my feet, make allowance for subject brightness and contrast, and -- more often than not -- set the camera at the hyperfocal distance for my chosen aperture. But now... Set a decent digital camera to "auto" and it beats my judgement 99 times out of 100, in a fraction of the time it takes me to say "Hmm, let me think..."

But. The one thing that virtually no digital camera has, and which every digital camera could really use, is a [HYPERFOCAL MODE]. It would be so easy! Assuming the camera's software knows the focal length and aperture currently in use, why on earth can't it do a moronic little hyperfocal calculation, and set the focus accordingly?

I keep re-reading camera manuals to see whether I've missed it or whether they've called it something cute like [FOCOMAT] or buried it in the "scene modes" somewhere, but no. I believe some Ricoh cameras do have this feature. Even the crude three settings for "zone focussing" that used to figure on ancient film cameras (flower! / people!! / mountain!!!) could be handy.

Perhaps there's a technical obstacle? My suspicion is that enabling the lens to be focussed at an actual pre-determined distance -- rather than reactively to whatever is detected by the camera's fancy focussing matrix -- may be too great an engineering problem to be worth tackling. If so, what a shame.

But I will send a free A4 print of the image of your choice to anyone anywhere in the world who can show me how this can be done (by simple software settings) on any one of these cameras: Canon 45oD, Olympus E-P1, Panasonic LX3, Panasonic GF1!


Hyperfocal-ish... But, no matter how great the DOF, nothing
will stop the wind blowing stuff out of focus...


9 comments:

Bronislaus Janulis said...

Mike,

I have no idea how to solve your problem; though I do note that small sensor cameras generally have great depth of field; more often trying to have some out of focus areas is the problem ... I basically don't worry about hyperfocal distance anymore.

Diffraction, however ... 8-)

Mike C. said...

But I thought you large-format types like to worry about such things! I like the "set and forget" aspect of the hyperfocal approach to landscape.

I've never understood this thing people have about "bokeh" and large apertures... I find most blur annoying. One of the main things I enjoyed about small sensor compacts was the wonderful depth of field,front to back, at any moderate aperture.

Mike

ottluuk said...

Ricoh (at least on the GRD - III) has this right. When you switch to manual focus, a distance scale appears on the display. It has an indicator for the actual focus point and around it, a green bar to indicate DOF. When you stop down, the bar lengthens accordingly. Simple, effective, practical.

Why the other manufacturers don't do this is beyond me. It is not hard to make a lens that can send back focus distance data to the camera. As far as I know, most of the modern Canon EOS lenses do it (to help the fancy flash metering system fail a little less).

Some Canon film SLRs had an A-DEP mode where you could use the spread of the AF points to choose a close and far object that you wanted to be sharp at the same time and the camera would focus somewhere between them and stop down appropriately. My plastic fantastic EOS 3000 had something in this vein...

Oh... wait... I just checked and this mode is still there on the 40D. So, obviously it must be cumbersome enough that I've never really used it. Especially since all my lenses have actual distance scales.

But then again, the distance scales on my lenses from 1987 indicate appropriate sharpness for a full film frame. So, a Ricoh-style on-screen DOF scale would still be useful, if it was calibrated to suit the 10MP APS-C sensor inside.

Mike C. said...

Yes, ottluuk, the Ricoh approach is not a bad way of doing it, but no, your "full frame" engraved scales are no good on a 1.6 reduced sensor camera.

What I really want, though, is simply to put the camera in [HYPER MODE] and have it automatically change the focus to match the current focal length and aperture -- it would be progress, too, as you could never really do the hyperfocal trick with zoom lenses, but I can't see why a digital camera couldn't.

Mike

Gavin McL said...

Mike

I can't help with your cameras but I use hyper focal focusing on my Nikon D40 as it will take manual lenses. I have a 24mm lens dating from the late 70's early 80's I think. In manual mode set the aperture on the lens, set the focus using the aperture markings one stop down i.e. for f16 use f11 (this takes care to an extent of the smaller sensor. I then set the shutter speed using the thumb wheel and the iso with the function button. It works well and gets around the D40 rather limiting 3 focus points. But it doesn't answer your question. Good luck on your quest but I suspect it might be a touch folorn.

Graham said...

But Mike, you can with your LX3!

I too have an LX3. As you might expect, set the focus switch to MF. As you move the focus point back and forward by using the little joystick up and down, a yellow indicator marker moves up and down. The thickness of this marker indicates the depth of field! So if you set a reasonably small aperture you will have a nice thick bar, which you can move about until the top of the yellow marker sits on infinity. At f5.6, my LX3 tells me I have a DOF running from about 0.75m to infinity. If you have the latest firmware (v2.1) you can set the ‘MF resume’ and even the ‘zoom resume’ so that every time you restart the camera your ‘hyperfocal’ position is automatically set. I think that is a pretty neat function and shows that someone at Panasonic actually uses their camera. It means that you can be really quick in busy situations, and just flick the focus switch to AF if you want to focus on something closer and more static. And no, you didn’t miss it in the user manual; it’s something that Panasonic forgot to tell us about. I think I found it on one of those dreadful camera fora when researching about the firmware update last year.

Mike C. said...

Graham,

That's intriguing, I'll give it a go. I must admit I've never used manual focus on the LX3. A quick fiddle just now didn't show the yellow bar increasing in thickness, just moving up and down, but a late night interior is not the obvious place to try this out.

Just when I was trying to wean myself off that camera!

Thanks,

Mike

(My offer stands -- if there's anything you'd like on the blog, email me your details and a genuine fade-guaranteed A4 dye print is yours!)

Bronislaus Janulis said...

Mie,

About the only time I can think of having a blurred background is a portrait, and that is rare, ... though my real feeling is that the automation, even in aperture preferred, gives me more of a focus on the actual composition. I'm also obsessively non- obsessive about the tech aspects of photography ... too much time in the darkroom as a young man. I'm down to two cameras, one in the car, and the serious, field camera, the Canon G9,... and I'm not upgrading til the little wonder breaks. The "pro" stuff I do, documentation of art, the G9 is absolutely superb for, and in fact, would completely dismiss any DSLR in lieu of it ... that 3" lCD is very much like a view camera.

Gavin McL said...

Pleased to be proved wrong