A Newbie's Question about Aperture

[Felix_Infelix]

Hi there, I'm new to photography as well as this forum, so I'm sorry if this question is a bit stupid!

I had been wondering about the use of large apertures in landscape photography. I know the general rule is to use around F11 or smaller when shooting landscapes so as to achieve maximum depth of field, but I am unsure if there is a reason why not to use larger apertures under certain circumstances.

Say I am using a wide angle lens at 12mm, and have my tripod set up on an overhang of rock so nothing closer than a few meters away is in the frame - if I set my aperture to 4.5 and focus at infinity won't everything be in focus (as there is nothing close enough to be out of focus)? Will I not get the exact same depth of field that I would achieve with F11?


I imagine I'm missing something pretty obvious, hope someone can help - thanks!

 

[nycphotography]

It's all about sharpness.

Most lenses are sharpest in the middle apertures. check the reviews and specs for your lens, and then try to shoot in it's "sharpness sweet spot" aperture range. At least for landscapes.

 

[tirediron]

It's all about sharpness and acheiving the end result you want. Generally speaking landscapes are shot with maximum DoF, however there might well be a reason that you don't want the full image in focus. Taking into account that DoF consists of areas that are [very] roughly equal in front of and behind the point of focus, you may want to focus somewhere other than the actual subject to achieve the DoF and look you want. Check out this calculator for more information.

 

[Goldcoin79]

Say I am using a wide angle lens at 12mm, and have my tripod set up on an overhang of rock so nothing closer than a few meters away is in the frame - if I set my aperture to 4.5 and focus at infinity won't everything be in focus (as there is nothing close enough to be out of focus)? Will I not get the exact same depth of field that I would achieve with F11?


I imagine I'm missing something pretty obvious, hope someone can help - thanks!

Felix_infelix this is the exact question I have been wondering about lately, as he says if he sets the aperture to 4.5 and focus at infinity won't everything be in focus?

 

[nycphotography]

Say I am using a wide angle lens at 12mm, and have my tripod set up on an overhang of rock so nothing closer than a few meters away is in the frame - if I set my aperture to 4.5 and focus at infinity won't everything be in focus (as there is nothing close enough to be out of focus)? Will I not get the exact same depth of field that I would achieve with F11?


I imagine I'm missing something pretty obvious, hope someone can help - thanks!

Felix_infelix this is the exact question I have been wondering about lately, as he says if he sets the aperture to 4.5 and focus at infinity won't everything be in focus?

Just because it's in focus, doesn't mean it will be at the lenses sharpest.

 

[Designer]

Say I am using a wide angle lens at 12mm, and have my tripod set up on an overhang of rock so nothing closer than a few meters away is in the frame - if I set my aperture to 4.5 and focus at infinity won't everything be in focus (as there is nothing close enough to be out of focus)? Will I not get the exact same depth of field that I would achieve with F11?


I imagine I'm missing something pretty obvious, hope someone can help - thanks!

Felix_infelix this is the exact question I have been wondering about lately, as he says if he sets the aperture to 4.5 and focus at infinity won't everything be in focus?

A lot of the answer will depend upon the focal length of the lens, and where, exactly, is the point of focus.

In his example, the the entire range of subject matter is only a few meters, so he didn't need to focus at infinity, IMO.

 

[Felix_Infelix]

It's all about sharpness.

Most lenses are sharpest in the middle apertures. check the reviews and specs for your lens, and then try to shoot in it's "sharpness sweet spot" aperture range. At least for landscapes.

Okay, that's helpful - thank you. However, that doesn't mean to say that using the lens outside of its "sweet-spot" for sharpness will result in unnacceptably poor photographs right? Assuming you're using a quality lens and the sharpness at larger apertures remains reasonably acceptable, then opting for a larger apeture (to compensate for lighting conditions, etc) will not result in out-of-focus images when shooting landscape. Are there any other reasons then (besides possibly not getting the absolute best sharpness) to use this technique then?

Say I am using a wide angle lens at 12mm, and have my tripod set up on an overhang of rock so nothing closer than a few meters away is in the frame - if I set my aperture to 4.5 and focus at infinity won't everything be in focus (as there is nothing close enough to be out of focus)? Will I not get the exact same depth of field that I would achieve with F11?


I imagine I'm missing something pretty obvious, hope someone can help - thanks!

Felix_infelix this is the exact question I have been wondering about lately, as he says if he sets the aperture to 4.5 and focus at infinity won't everything be in focus?

A lot of the answer will depend upon the focal length of the lens, and where, exactly, is the point of focus.

In his example, the the entire range of subject matter is only a few meters, so he didn't need to focus at infinity, IMO.

Sorry, I mean in my example that I am shooting from an outcrop (from a edge of a cliff, for example).

 

[Designer]

Oh, thanks for pointing out my error. Now I agree that you should focus at infinity, but there is one more thing to consider:

Under "normal" landscape conditions, i.e. daylight, one should hardly find any reason to shoot wide open. So why not close it down to the limit of your shutter speed? If hand-held, no slower than the reciprocal of the focal length of the lens. In the case of 24mm, you could theoretically shoot with a 1/25 of a second shutter speed, HOWEVER, you still should not try hand-holding such a slow shutter speed. Anyway, that gives you plenty of stops in your aperture to play with.

 

[TCampbell]

At 12mm you picked a fairly extreme example. A wide-angle lens will naturally have a very high depth of field even at low aperture values.

This topic came up a last fall, so I grabbed my 14mm lens, set the camera to f/2.8, walked out of my house and candidly snapped this shot:


Maple in Autumn by Tim Campbell1, on Flickr

It's not focused all the way through... but it is close. The thing to note is that this was taken at f/2.8 -- on most lenses that would offer a fairly narrow depth of field, but not on a wide angle lens (and this was a full-frame DSLR.)

Would it have looked better at a higher f-stop? Yes. The MTF tests on this particular lens model show that the "center" has the highest resolution at f/4, but the edges and corners look best at f/8. Had I shot this at f/8 (or even f/5.6 or f/4) it would have been improved slightly. I took this at f/2.8 specifically to demonstrate that very wide lenses have extremely generous depths of field even at low focal ratios.

You generally never want to focus to "infinity". There's a concept known as the "hyper-focal distance". The idea is that from your focused point, some area both in front and BEHIND your focused point will also have acceptable focus. But if you focus to infinity, there's nothing "behind" infinity. By focusing a little forward, you get even more of the foreground in focus and you still have all the background in focus.

The "hyper focal distance" is the point which will maximize the focused area. It will be different at every focal length and focal ratio (aperture). It used to be easy to dial in manually by just looking at the depth-of-field index marks on the lens. But in the days of auto-focusing lenses, the DoF index marks are often not included anymore. You can use a website or download an application to a smartphone to find the hyper-focal distance. The website DoFMaster.com has tools for this. They also sell an app for smartphone users (I think they charge a very small fee for their app, but there are some which are free.)