Small aperture values and sharpness

[Thaash]

If I use a very small aperture opening like F/20 do I have the same sharpness on a lense as when using its the aperture in its widest opening +2 Value (e.g.: at a 2.8 Lens 5.6 is thouth to be the sharpest)?

I am asking in terms of nature shots. Basically according to the Hyperfocal distance calculations if I use a very small apertrure opening everything from a given distance will be sharp. Does it work? (I need the extra small aperture opening to use with water shots together with my ND8)

 

[Big Mike]

There is almost always a 'sweet spot' in the aperture range when it comes to sharpness...it's usually around F8.

Keep in mind that it's two separate things...loosing sharpness because of the aperture value and being out of focus.
Using the hyper-focal distance is about focus. And the idea is to find the aperture & focus distance that will give you the widest DOF.
However, as you stop down the lens past it's sweet spot, you are likely sacrificing sharpness. I think it's because of the diffraction as the light is bent to go through such a small hole and back to the film/sensor.

One of the benefits of using the hyper-focal distance, is that you can hopefully discover the maximum aperture that you need to get your scene in focus....so that you don't unnecessarily use a very small aperture. In other words, if F8 will give you the DOF that you need...there is little reason to use F22 (unless you specifically want a longer shutter speed).

 

[o hey tyler]

Depending on the quality of the lens, you may have good sharpness throughout your frame. If you have a consumer grade lens, you may find that you lose sharpness after a certain point (I.E. after the sweet spot). When the opening is too small, diffraction occurs. Which may lead to less than sharp images.

\\EDIT: Mike seems to have beaten me to the punch with a more in depth explanation. LAWLS.

 

[Breaux]

Big Mike is fast!

 

[KmH]

If I use a very small aperture opening like F/20 do I have the same sharpness on a lense as when using its the aperture in its widest opening +2 Value (e.g.: at a 2.8 Lens 5.6 is thouth to be the sharpest)?

I am asking in terms of nature shots. Basically according to the Hyperfocal distance calculations if I use a very small apertrure opening everything from a given distance will be sharp. Does it work? (I need the extra small aperture opening to use with water shots together with my ND8)

It depends on the construction of your lens and a property of optics known as diffraction (airy disc). Diffraction will soften focus at small apertures. http://en.wikipedia.org/wiki/Diffraction
http://en.wikipedia.org/wiki/Airy_disk

Other factors effect lens sharpness at wide open apertures.

 

[Derrel]

"widest opening + 2 Value"...ahem....Let's put that into proper photographic terminology,okay?

"Many lenses perform best when stopped down two f/stops from their widest aperture." Or how about, "Many lenses perform best when stopped down three f/stops from their maximum aperture."

Using a positive increase in numerical "Value" as a way to refer to stopping a lens down to a smaller aperture is simply a bad idea.

 

[dxqcanada]

Big Mike is fast!

Big Mike has a neural shunt.

 

[maris]

If I use a very small aperture opening like F/20 do I have the same sharpness on a lense as when using its the aperture in its widest opening +2 Value (e.g.: at a 2.8 Lens 5.6 is thouth to be the sharpest)?

I am asking in terms of nature shots. Basically according to the Hyperfocal distance calculations if I use a very small apertrure opening everything from a given distance will be sharp. Does it work? (I need the extra small aperture opening to use with water shots together with my ND8)

If your subject has many objects spread over a wide range of near to far distances then using a very small aperture will give you more details. The details won't be as sharp as you would get at the optimum aperture because diffraction will bite. But your picture will carry a convincing impression of apparent sharpness. Out-of-focus because of insufficient depth of field looks much worse than diffraction.

And by the way put the camera on a tripod. You will probably be using slow shutter speeds to go with the low ISO values that deliver maximum quality.

 

[mhk1058]

If your using a relatively short focal length for landscapes(water shots?), you can get perfectly adequate hyper focal distance values at f16 with an 18mm lens (just over 3 feet HFD, or 18 inches near focus point) Even at f11 evrything from just over 2 feet can be in focus. With shorter focal length it will be even closer. So no need to use f20, where, as others have said, you will get diffraction, causing softening, as the light is 'bent' round the small aperture, even f16 can be pushing it with a lot of lenses.

 

[JG_Coleman]

I use f/18 to f/22 quite often. Sometimes, it's because there is simply a lot going on in a scene with a whole lot of depth and I just need everything to be in focus. More often, it's because I'm trying to slow down my shutter speeds to get long exposures at waterfalls, rivers, and seashores. In those situations, sometimes using an ND filter in tandem with dropping my ISO to 100 (the native on my camera is 200) just isn't enough to slow down my shutter sufficiently.

However, with the exception of these situations, I try to stay between f/8 and f/11. And, in between, f/14 is a decent compromise between deep focus and sharpness.

On a 1:1 look, f/20 and f/22 unquestionably produce softer edges and resolve less detail than, say, f/11. Take a look at the comparison below:

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Full Image (f/11 versus f/22)

1:1 Image (f/11 versus f/22)

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The smaller viewing sizes here make it tough to realize the differences to their full degree... but it should suffice. Notice that, at reduced viewing sizes, both images seem to look almost identical.

But at 1:1 view, it is pretty clear that f/11 is producing superior detail. If I only made, for example, a 5"x7" print, then the difference between the two shots would not really even be noticeable. But the larger the print, the more the difference in sharpness will start to show.

It's a trade-off, really. With many scenes that I shoot, the limited depth-of-field offered by f/11 just wouldn't cut it... in others, it'd ultimately be poor craftsmanship to unnecessarily use a tiny aperture and sacrifice detail. But the difference is very real... and choices for the best f-stop need to be consciously assessed on a situation-by-situation basis if your goal is to get the best shot.

In situations that strike me as being borderline, I'll oftentimes take shots at two or three different f-stops (ex. f/8, f/11, f/14 or f/11, f/14, f/20) and make choices about which worked best when I can pull the RAW files up in PP, take a closer look than my live view offers, and weigh the varying sacrifices in 1:1 detail against deep focus.

EDIT: It's also worth pointing out that these photos were taken with the Nikon 18-55mm kit lens. When using my higher-quality Nikon 10-24mm (a lens so wide that it suffers from its own inherent set of issues), I've noticed that the reduction of sharpness at small apertures is still present, but not quite as pronounced. So, based on my experiences, a higher-quality lens does make a difference... but it's impossible to dodge diffraction altogether.