Auto and f stops.

[petrochemist]

No better way to confuse a beginner than to present them with a "rule of thumb" that's false. I've encountered that 1/3 -- 2/3 rule before including long before. I've looked into it carefully and it's bogus.

Joe

It is indeed false, varying between nearly 1:1 at macro distances and infinity:1 when focusing all the way out. However at moderate distances where portraits are taken its reasonably close. Many years back when i was a beginner, without a DOF preview or rangefinder/measure, I found it useful.
For landscapes 1/3 of the way was more of an anglular ratio than a distance one(something that I believe I was told when introduced to the 'rule'). As I started taking closeups I found it no longer applied but an estimated third was a fair compromise for most shots.

A rule of thumb doesn't have to be accurate to be useful. I suspect I still subconsciously use it as a starting point for many shots, making it closer to half way as I get closer in. Things like this only confuse if you treat them as gospel.

As a rule of thumb it's been around a long time. I was presented with it when I was a beginner and that's over 50 years ago. I'm not sure of it's origins but if you spend some time with a DOF simulator you're going to have a hard time finding any kind of general use scenario where it comes close to applying. What would be an example: Put a 50mm lens on a 35mm camera (not too common any more but it was). Go out on a sunny day with some friends and have two friends stand in front of an attraction -- say a fountain. Stop the lens down to f/11 (that's why I said sunny day) and frame your two friends side by side full body with some room to spare. You'll be about 8 or 9 feet away and that's .33 -- .66 DOF distribution.

But for portraits we're going to get closer by hopefully mounting a longer lens. We're not going to use f/11 and very quickly DOF distribution is headed for .49 -- .51. For portraits it's much better to rule of thumb the DOF distribution as 50/50. For landscapes and cityscapes a much better rule of thumb would be to just say most of the DOF will be behind the focus point. Put a 35mm lens on a 35mm camera, stop down to f/8 and shoot a cityscape and 95% of the DOF is behind your focus point.

We've all noted it's an old rule. I used to shoot sheet film and 120 roll film 35 years ago. Landscapes with those bigger formats had less DOF than what I get from a modern smaller format digital camera and a .33 -- .66 distribution may have been more common. Here's another rule of thumb: Almost nobody does that anymore. The progression of technology has been an unrelenting move toward smaller formats and with that comes increased DOF. Portrait photographers make an effort to keep the background blurry. To do that they use larger f/stops and send the DOF distribution straight to 50/50 even with smaller cameras like APS formats. For the rest of us with smaller sensor cameras used "generally" a much more useful rule of thumb is most of the DOF will distribute behind the focus point.

So we're teaching beginners and want to help them with a useful rule of thumb using modern cameras. Rule: Try and focus about 1/3 into your subject for maximized DOF placement. Or rule: Focus on your subject. If you want deep DOF use a small f/stop and if you want shallow DOF use a large f/stop.

My biggest gripe with the 1/3 -- 2/3 rule of thumb is that some beginners try to apply it and that invariably screws them up.

Joe

It was only 35-40 years ago that I was routinely shooting with a 50mm on a 35mm SLR. The rule worked reasonably well then - there were no DOF apps, that camera had no DOF preview. Where I needed better accuracy I could make use of the markings on the lens, but that needed measurements rather than just eyeballing.
FWIW 5-10 foot subject distance would have been very common back then.

 

[Ysarex]

Didn't the 1/3 application have to do with placement of the focus in the viewfinder, not necessarily the actual distance? In other words, on a landscape shot where there's foreground, medium distance and horizon, focus on an object around 1/3rd up and set a relatively small aperture. Or between the closest and furthest point you want in focus, again 1/3 up from the closest. That would get you in the ballpark for a quick shot.

Yes, and I often encountered the rule presented that way. I noted it in that form just above. Focus into the subject approx. 1/3 is often how you'll hear it presented. That's a bad suggestion that will usually lead to poor results. Which is why I've taken the trouble to note it here. Much better: Select the closest object in your scene that you want in focus and focus on that object.

Joe

 

[fmw]

We sometimes lose sight of the fact that true sharpness occurs at only one plane. Areas of the subject that are not at that plane can only be acceptably sharp, never perfectly sharp. I recommend using the monitor on your camera to see the depth of field directly. You are the one who decides what is acceptably sharp.

I use a screen magnifier to view the monitor for critical depth of field requirements. They aren't all that expensive and are a useful accessory for your camera bag.

 

[Grandpa Ron]

Interesting reading but when you get beyond what looks good to you, you have entered the world of opinion.

The more I deal with digital, the more I find the double edged sword. Flipping through the various dial presets, I find that the camera folks have studied the market and decided that certain pre-sets are the most acceptable to the user. I chuckled when I had a dial position for food photos ( I never would of though of that). Still they do a pretty good job of second guessing my preferences. When they don't I which to Manual.

The other edge of the sword is, with post processing, you can do whatever to want to that digitized image regardless of what the camera maker thought it should look like.

I have heard discussions of what a lens, cameras, , tripods, flashes, films and now post processing programs should or should not do. All of these should do what you want; unless you are a professional photographer. The pros have to do what sells.

 

[petrochemist]

I have heard discussions of what a lens, cameras, , tripods, flashes, films and now post processing programs should or should not do. All of these should do what you want; unless you are a professional photographer. The pros have to do what sells.

Surly for a pro, what they want generally is 'what sells' - it might not be to their taste but they have to cater for their customer, one of the reasons I'm not a pro. Others are that I often don't get my kit to do quite what I'd want, my people skills aren't good enough & I like the work I do...
Being free to try what I fancy is much better for me, though I would like to get a financial return on my kit investment.

Fortunately for their sanity, pros can take shots purely for their own pleasure. I've admired many of them on forums like this, while I'd probably have much less interest in the ones that sell.

[Sorry for drifting off topic]