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If f/8 And Be There is the rule for 35 mm, what is the best f/stop if I am using 50mm?

Context: Street Photography

Note: Though one can say that "it depends", this is a very specific question. When compared to 35mm-f/8, what is the combination for 50mm?

Comment from f/8 And Be There

As an example a 35mm lens set at f/8 and focused to about 17 feet will have everything between 9 feet to infinity in reasonably sharp focus.

On the other hand, a 50mm lens set to the same values would have everything from 11 feet to 34 feet in focus, while a 21mm lens would have everything from 4.5 feet out to infinity in focus

Another Comment from f/8 And Be There

“f/8 and be there” is a philosophy that's and dear to every documentary photographer’s heart, be they Street Photographers, Photo Journalist, or Travel Photographers. Of course this leads to another question…What on Earth was Weegee talking about?

“f/8 and Be There” is a very simple statement that addresses two very important aspects of documentary photography. The first is technical, the second a bit more philosophical.

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    From the point of view of exposure, there is no difference. f/8 is f/8 regardless of the focal length - the physical aperture size may vary, but the effect on exposure is the same. Are you looking for equivalent depth of field instead? In which case please specify in your question. Thanks! – NickM Sep 30 '14 at 15:35
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    You're overthinking this. It's a rule of thumb. f/8 will do just fine at 50mm. – Philip Kendall♦ Sep 30 '14 at 15:38
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    The phrase "f/8 and be there" goes back to crushed fedoras, 4x5 press cameras with 135mm lenses and #25 flashbulbs. It's a Weegee line, meaning that being there to get the shot is more important than the technicalities. You want zone focus/prefocus? Figure out your near and far limits (the situation will dictate that), and set the focus distance and aperture appropriately. (You will need focus and DoF scales on your lens.) – user32334 Sep 30 '14 at 16:22
  • Are you shooting full frame or crop? :) – inkista Sep 30 '14 at 18:39
  • @inkista I am using Olympus E1 which is a Four Third Format – LCJ Sep 30 '14 at 19:36
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To achieve the same depth of field with a 50mm lens, you would have to set your aperture to f/16.

I would like to explain hyperfocal distance to you.

In case of an 35mm lens with f/8 the hyperfocal distance is 5m (17 ft). It means, you can not focus closer and still keep infinity (reasonably) sharp. If you would focus at 2m (6.5 ft), the far limit of your depth of field (DoF) would only be at 3m (10 ft).
Since in the first exapmle you focus on something 5m (17 ft) away, things in front of it might as well be in focus: Your DoF would extend from 2.5m (8 ft) past 5m (17 ft) to infinity (180m or 590 ft, to be exact). It is practically the greatest DoF at that aperture. That is the concept behind "hyperfocal distance".

You should still consider not using f/16 on a 50mm lens. Although you might get the same DoF, typically the quality of a lens is best around f/8. Jumping to f/16 might result in more chromatic aberration and less resolution (on the lens's side, so a blurrier image). The quality loss is not dramatic, but keep that in mind.

If I was to shoot street photography with a 50mm (equivalent) lens, I would set it at f/11 and focus to around 7.5m (25 ft). Your DoF would stretch from 4m (13 ft) to infinity (again: exactly 451.81m or 1,482.32 ft :) ). That way you would minimize the risk of losing a shot due to bad focus.
Nevertheless, there might be times I would set my nifty fifty to f/1.8 and savor the bokeh-liciousness I do not get with the approach above.

The tool I used for calculating all those DoF distances.

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  • Please explain why in the heck infinity is important, or even relevant, for street photography. – user32334 Sep 30 '14 at 22:33
  • @user32334 In my understanding: maximizing the DoF == maximizing the chance of having your subject in focus, regardless or its distance to you (which you often can't anticipate in street photography). But yes, you probably don't really need something 180m back to be in focus. – icecrime Oct 2 '14 at 8:41
  • "Maximizing the chance of your subject being in focus" would be bringing the inboard limit in as far as you can without losing the far point, and where that far point lies depends on the space you're working in. (Actually, a better tactic would be to get critical focus as close as possible to the expected subject range, and adjust aperture to fit the expected far point in. The subtle increase in sharpness/acutance at subject position becomes an effective but nearly invisible compositional element.) – user32334 Oct 4 '14 at 20:01
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The "f/8 and be there" rule, for a 35mm lens on a full frame camera is really about the hyperfocal distance and the distance from which everything in your shot will be in focus. So with those settings, one could expect that without having to focus at all, if you're at the right place at the right time, your subject/scene will be in focus, and thus save you time when trying to capture the shot.

Admittedly, you'd probably set your camera in Aperture Priority, Manual Focus, to achieve the same effect (and let the camera decide ISO and Shutter speed for you. Or just the shutter speed if you fix the ISO).

So if I understand your question properly: How do I get the same Hyperfocal distance at 50mm on my camera? Depends on the Camera, since Full Frame/APS-C will give you different hyperfocal distances for the same focal length and aperture.

So look at the DOF Calculator here, enter your camera, focal length, choose an f-stop, and look on the right side for the hyperfocal distance. For example, taking the 5D Mk II, focal length of 35mm, f/8, the hyperfocal distance is written as: 16.9ft.

Same camera, switch to 50mm, the hyperfocal at f/8 is 34ft. To get back at a distance of approx 17ft, play around with the f-stops, and it says: f/16.

And if you take the Olympus E-1, Focal Length 50mm, then the aperture you need to use for a 17ft hyperfocal distance ends up being... f/32.

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The rule is about the hyperfocal distance, about setting your aperture such that you don't have to spend any time on focusing and thus can take pictures very quickly and spontaneously. With today's fast autofocus, it's much less important.

The answer to your question is: it depends, because you're not, in fact, specific enough. It still depends on your sensor - the "f/8 rule" assumes a 35mm film camera as well as a 35mm lens.

You can use the online DoF calculator to get a specific answer. For example, if I choose a Nikon D4, a 50mm lens and then try out different apertures, I see that I get the desired effect (in the bottom graphic, "Depth of field extends from 8.65 ft to infinity") with an aperture of f/16.

And if you take the Olympus E-1, Focal Length 50mm, then the aperture you need to use for a 17ft hyperfocal distance ends up being... f/32.

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First of all, "f/8 and be there" is an old photojournalist adage. Basically, it's more important to be "there" then how technically proficient you are.

Second, your settings actually do depend on the situation. f/stop is more important than focal length (all though the two can affect each other).

More importantly, what is your ISO and shutter speed in relation to your f/stop. This determines exposure. Remember that each one affects the other. In other words, if you find that f/8 is working for you at 1/250, and you decide you want to try f/5.6, then make sure you speed up your shutter by the same amount of stops you opened up your aperture.

For street photography, just keep in mind where you're at. Change one, then change the other.

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    I think you're missing the point of the question. f/8 is not about exposure, it's about the hyperfocal distance. – Michael Borgwardt Sep 30 '14 at 17:35

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