Shooting Challenge: One Focal Length Exposures

Illustration for article titled Shooting Challenge: One Focal Length Exposures

Ever take a handheld photo that you thought was amazing, only to see it larger and realize that you totally blew it by shaking the tiniest bit? Well, you can limit these mistakes using a simple rule.


The Challenge

Take a handheld photo using the one focal length trick. (described below!)

The Technique

We know, the tripod is the surest way to get a perfectly sharp photo, but what about 99% of the time when we shoot handheld? How are we sure we get the sharpest possible shot?


There's an old trick to make sure you're using a fast enough shutter speed all the time, no matter what camera you pick up with any lens. It's called the 1/FL or 1/focal length rule, and it basically states that you can turn your focal length (or lens) into a fraction that becomes a suitable exposure speed.

So a 35mm lens equals a 1/35 exposure. A 100mm lens equals a 1/100 exposure. The principle is simple: The wider your lens (the less zoom), the slower you can photograph. And that makes a lot of sense when you think about it. Zoomy shots always have more potential for blur, much like the slightest shift of a sniper rifle will miss a target miles away.

Of course, like any simple rule, things become more complicated quickly. It's a colloquial method, and many argue that you actually need to shoot 1/2xFL for a perfect, enlargeable print. (1xFL for a small print, 2xFL for big one.) That means a 35mm lens needs a 1/70 exposure. A 100mm lens needs a 1/200 exposure.

Then it gets even trickier when we start talking cropped sensors—the sensors you have in your midrange SLR that aren't "full frame"—because the number printed on your lens isn't really its field of view anymore. Personally, I think 1/2xFL is a usable solution day to day. But if you want to get extremely technical, search for your camera's "crop factor," then match it to your lens on this conversion chart to find your new ratio. (I find this approach a bit overkill for a few technical reasons that may or may not approach pseudo science.)


Use any of the three FL rules you prefer—I'd recommend 1/2xFL. Just know what you're doing and explain it in your submission. The idea is to test and learn.

The Example

Illustration for article titled Shooting Challenge: One Focal Length Exposures

I quickly snapped the lead shot out my window at a B&B in St. Andrews. It's unedited and unremarkable. But I actually snapped it at two different shutter speeds. At an 18mm focal length, I shot it at 1/20 and 1/40. I've cropped a side by side here (1/20 on left, 1/40 on right) and left the division noticeable. Is it night and day? No. But look at the stone on each side of the line. See how much more detail you're getting separating each rectangle? OK, OK, part of that may be due to an ever-so-slightly better contrast, but it's also the quicker exposure. We're talking about differences at the pixel level that add up to an overall better, more detailed photo.

The Rules

1. Submissions need to be your own.
2. Photos must be taken since this contest was announced (read more on that above).
3. Explain, briefly, the equipment, settings, technique and story behind shot.
4. Email submissions to, not me.
5. Include 970px wide image (200KB or less) AND a 2560x1600 sized in email. I know that your photo may not fall into those exact high rez dimensions, so whatever native resolution you're using is fine.
6. One submission per person.
7. Use the proper SUBJECT line in your email (more info on that below)
8. You agree to the Standard Contest Rules - though we DO accept non-US resident submissions.
9. If the image contains any material or elements that are not owned by you and/or which are subject to the rights of third parties, and/or if any persons appear in the image, you are responsible for obtaining, prior to submission of the photograph, any and all releases and consents necessary to permit the exhibition and use of the image in the manner set forth in these rules without additional compensation. If any person appearing in any image is under the age of majority in their state/province/territory of residence the signature of a parent or legal guardian is required on each release.


Send your best photo by Monday, September 10th at 10AM Eastern to with "One" in the subject line. Save your files as JPGs, and use a FirstnameLastnameOne.jpg (970px wide) and FirstnameLastnameOneWallpaper.jpg (2560px wide) naming conventions. Include your shooting summary (camera, lens, ISO, etc) in the body of the email along with a story of the shot in a few sentences. And don't skip this story part because it's often the most enjoyable part for us all beyond the shot itself!

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The formula doesn't actually do much to give any sort of accounting for aperture. I tried this with a 17-50 at 17mm f1:2.8 1/15 and at 50mm f1:2.8 1/50 and both shots were completely and totally blown out white. shooting 17mm f1:32 1/15 and I was a stop too dark and 50mm f1:32 1/50 was at least 2 stops too dark. Not too sure this particular rule is going to be much help. It's better to determine your shooting needs, how much detail vs how large of an envelope for focus, to pick your apeture, adjust you shutter speed from there to get the right exposure. And keep in mind, shooting with a 50mm-200mm f1:4 is a fair bit different than shooting a 50mm f1:1.4 in a case like that the speed of the glass drastically changes what speed you shoot at, and quite frankly if you are shooting with a f1:4 you really just need to carry a monopod/tripod with you all the time.