Aperture size for landscape

[Alis]

Quick question: what are the parameters for determining the f number when shooting landscape? I assume we choose a high f number to increase the depth of field. So, why the usual f11 and not as high (small) as possible, say f22? What is the trade off?

An would using a higher f number decrease vignietting when stacking multiple filters or it has more to do with the focal length used?

Thanks!

Alis

[KentDub]

I try to shoot them a stop or two less that the smallet apature. This keeps the more in focus (larger DOF) but avoids the typical distortion of lenses when reaching extremes of its F-stop range. The "Understanding Exposure" book I read (recommend from these forums) refers to F/8 and F/11 as "who cares" stops.

I'm still learning this so I'm interested to see what others have to say

[Alis]

I try to shoot them a stop or two less that the smallet apature. This keeps the more in focus (larger DOF) but avoids the typical distortion of lenses when reaching extremes of its F-stop range. The "Understanding Exposure" book I read (recommend from these forums) refers to F/8 and F/11 as "who cares" stops.

I'm still learning this so I'm interested to see what others have to say

Hi Kent,

But I am more talking about the other extreme, very high f numbers or very small apertures. For landscape you will always be way above the lowest aperture for the lens anyway but my question was why not go up all the way?

[JK6065]

I spoke a local photographer today and he said to me that a lower F stop was better.
The reason why, he said, is that when light comes in to the sensor in a comparatively high angle (at a very high F stop) you're able to see every dust particle on the sensor on your photo (I'm not sure if he only ment dust on the sensor or also dust on the lens). This could be true, and since he is a photographer for 9 years I believe him based on his experience, but I wonder why this works like that. Is there someone who could explain me some about this?

For myself I would stay in the 'save' range just because 'they' say so, and by 'they' I mean the writer of the article and the professional photographers.

[McQ]

Hi Alis,

Smaller apertures (bigger f-stop) give you more depth of field and sharpness, but too small of an aperture will begin to soften the image again due to diffraction. Diffraction is an unavoidable property of light when you send it through smaller and smaller apertures. There's a lot more on this topic in the tutorial on Diffraction & Photography. In between these two extremes there's a "sweet spot." In your case, f/22 would definitely near the diffraction extreme, but it might still be worth it in select cases if you need an extreme depth of field. If depth of field is less critical, then you'll probably get sharper results at f/11 to f/16 (although this depends on the particular camera lens you happen to be using).

There's a new article online which talks about this concept a little. The section which is probably most relevant can be found here: Camera Lens Quality: MTF, Resolution & Contrast

To answer your other question, a smaller aperture will do nothing to reduce physical vignetting caused by stacked filters. Small apertures only reduce optical vignetting (the gradual light fall-off from the center to the edges that is inherent to your lens design).

Hope this helps!

[Alis]

Thanks, Sean! Very helpful. I had a guess that there is something wrong with just going up as much as you can but did not know the reason.

It came up today when I was playing with the new Singh-ray VariND filter I received. I was thinking it only increases exposure by 8 stops, and I thought if that is all it does, why not go up on f as much as possible, as I see landscapse pictures are taken at f11 or so. But now I see the reason.

Thanks again!

[Alis]

I spoke a local photographer today and he said to me that a lower F stop was better.
The reason why, he said, is that when light comes in to the sensor in a comparatively high angle (at a very high F stop) you're able to see every dust particle on the sensor on your photo (I'm not sure if he only ment dust on the sensor or also dust on the lens). This could be true, and since he is a photographer for 9 years I believe him based on his experience, but I wonder why this works like that. Is there someone who could explain me some about this?

For myself I would stay in the 'save' range just because 'they' say so, and by 'they' I mean the writer of the article and the professional photographers.

Thanks, JK6065! I have heard the issue with dust and small apertures but do not know the reason either. I think that has a good physical explanation, I have forgotten most of the physics I have learned in high school. At the time, I knew a lot about optics but it was never practical. I still know a lot about optics of the human eye and glasses prescription

[Colin Southern]

Hi Ali,

This is kinda up my alley, so I'll throw in my 10c worth ...

The smaller the aperture, the greater the depth of field, but you really need to calculate your hyperfocal distances to work out what's the minimum you can get away with to minimise both diffraction & waiting time (for low-light) shots (not withstanding the need for a long exposure for other reasons, eg water effects, or the need for a narrow aperture to increase starbursts etc).

Often it comes down to what's the nearest thing in the foreground that you need to keep in focus - if nothing is particularly close then (not withstanding special cases) there's no reason to stop down past the lenses sweet spot (typically 2 or 3 stops down from wide open).

Case in point ...

A shot at 100mm @ F11 on FF camera - if you focus on something 30m away then everything from 15m to infinity (and beyond!) will be sharp. If you stop down to F32 the 15m comes back to about 8.5m - so if you have something in the 8.5 to 15m region that you need to be sharp then there's a reason to stop down - otherwise, don't worry about it.

Having just said all that though - 19 times out of 20 I find that I DO need to control something with a narrow aperture (in a world where everyong wants higher ISOs for lower light, I always struggle with the opposite - needing LOWER ISOs because I have too much light (in the context of long exposures).

With regards to diffraction - it's a very real thing of course, but in my opinion the effects of diffraction are very minor compared to what would happen if I didn't use a narrow aperture - also capture sharpening goes a LONG way towards countering it. In my opinion, if you need to stop down then just do it

Hope this helps!

[Alis]

...if nothing is particularly close then (not withstanding special cases) there's no reason to stop down past the lenses sweet spot (typically 2 or 3 stops down from wide open).

Thanks, Colin! Very interesting subject.

The surpirse for me is that you are recommending an f number of around 3.6 or so for landscape if I use a 2.8 lens if there is nothing particular in the foreground close to the camera. So when the camera focuses on the so called infinity (like couds) the picture will be sharp and focused. Is this correct?

[Colin Southern]

Thanks, Colin! Very interesting subject.

The surpirse for me is that you are recommending an f number of around 3.6 or so for landscape

3.6? - not quite - 2 or 3 stops down from 2.8 is F5.6 or F8.

So when the camera focuses on the so called infinity (like couds) the picture will be sharp and focused. Is this correct?

It depends on where you focus. DoF is a range both after and before the plane of focus - so if you focus on infinity then your not optimising the range in front of that point (or to put that another way, you can focus on an object a specific distance away that will mean that you've got things closer to you in focus but with things in the background STILL in focus.

You can really do it two ways - you can crunch the numbers (I have an app on my iPhone that's great for that) - or you just "play it by ear". A couple of examples ...

- When I took the Lone Tree Vista shot the other day I knew that if I was 15 metres or more from the tree - and focused correctly - then the tree and the background would be in focus @ F11. I paced out around 20 metres to the tree and thus didn't have to worry about a 12 minute exposure at F11 turning into an hour exposure (that wouldn't have worked anyway) at F22.

- With wide angle lenses the depth of field is so great it's actually harder to stuff the DoF up if you try - at 16mm @ F22 your Focus range is from 0.37m to infinity (or at 16mm @ F5.6 it's from 1.4m to infinity), so not something of overly great concern (you just need to be a little careful about where you focus if you have close foreground objects).

Make sense?

[Alis]

3.6? - not quite - 2 or 3 stops down from 2.8 is F5.6 or F8.

Hopefully I am not trivializing this discussion but looks like I am not counting correctly. On my 24-70mm f/2.8, f8 is 8 stops above 2.8, certainly not 2-3 stops!

[arith]

I always use f8, because it isn't diffraction limited and a full stop not half of one. The hyperfocal distance is reasonable at 28mm no problem. But sometimes I go to the trouble of working out dof and bang the aperture nearly as wide as it will go.

It just depends but I never go above f11, though I think a night shot might look better with smaller aperture since definition isn't an issue.

If that isn't confusing I don't know what is

[arith]

Hopefully I am not trivializing this discussion but looks like I am not counting correctly. On my 24-70mm f/2.8, f8 is 8 stops above 2.8, certainly not 2-3 stops!

I think it goes f1, f1.4, f2, f2.8, f4, f5.6, f8

or 1 times square root of 2 to the power 0

square root of 2 times the above = square root of 2 to the power 1

square root of 2 times the above= square root of 2 to the power 2
.
.
.
Where the powers are full stops.

It's easy stuff but not easy to explain I suppose without symbols.

[Alis]

I see, but on the lens I have 3.2, 3.6, etc. What about those?

[McQ]

Those are fractional f-stop increments, not full f-stops. Full f-stops is just one of those things that is often memorized: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc., as arith listed.

[Colin Southern]

Best way I found to remember them was to just do two lists and keep doubling, so

1 - 2 - 4 - 8 - 16 - 32 - 64 and

1.4 - 2.8 - 5.6 - "11" - "22" - "44"

... then just throw them together ... 1 - 1.4 - 2.0 - 2.8 - 4.0 - 5.6 - 8 etc

[Alis]

Thanks, Sean. That changes everything then


Thanks, Colin, for the memorizing tip!

[Colin Southern]

Thanks, Sean. That changes everything then


Thanks, Colin, for the memorizing tip!

No Worries Ali - for what it's worth, I set my 1Ds3 to only to whole F-Stop numbers, but allow shutter-speeds in 1/3 steps (I keep ISO to whole settings too); you could probably do that with the 5D2 if you wanted (at a guess).

[KentDub]

No Worries Ali - for what it's worth, I set my 1Ds3 to only to whole F-Stop numbers, but allow shutter-speeds in 1/3 steps (I keep ISO to whole settings too); you could probably do that with the 5D2 if you wanted (at a guess).

Do you have something against 1/2 or 1/3 stops? What's the reasoning?

[McQ]

For me, it just makes the math (and memorization) a lot easier. If I want finer precision with the exposure, I let shutter speed take care of that.