Wide aperture SHARP Narrow aperture NOT

[steinzeug]

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Sorry folks... this might seem very naive, but when i use my M8 and a summarit or summicron 50mm wide open the area of focus is razor sharp, however when i up the aperture to 4, 5.6 or higher, i get a deeper depth of field (of course) but, the area in focus is nowhere near as sharp as at 2, 2,5.

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[dpattinson]

Sorry folks... this might seem very naive, but when i use my M8 and a summarit or summicron 50mm wide open the area of focus is razor sharp, however when i up the aperture to 4, 5.6 or higher, i get a deeper depth of field (of course) but, the area in focus is nowhere near as sharp as at 2, 2,5.

 

So, there are a few possibilities - not knowing how you are testing this:

 

1. Stopping down, the shutter speed is falling to such a level that camera shake is blurring everything. (This assumes you're not using a tripod).

2. The lenses are possibly (I don't know) subject to some degree of focus shift on stopping down and at the apertures you're using the dof isn't enough to compensate.

3. You're noticing diffraction effects (although that certainly shouldn't be happening at f4).

4. You have auto-iso turned on and stopping down the iso is rising, resulting in noisier images which look less sharp.

 

Those lenses shouldn't get less sharp stopped down to f4 as far as I'm aware - could be wrong of course

[steinzeug]

.......

 

So, there are a few possibilities - not knowing how you are testing this:

 

1. Stopping down, the shutter speed is falling to such a level that camera shake is blurring everything. (This assumes you're not using a tripod).

 

No, i am using a tripod and looking at the focus depth

 

2. The lenses are possibly (I don't know) subject to some degree of focus shift on stopping down and at the apertures you're using the dof isn't enough to compensate.

 

The new summarit 2.5/50mm has apparently no major issues with focus shift

 

3. You're noticing diffraction effects (although that certainly shouldn't be happening at f4).

 

exactly

 

4. You have auto-iso turned on and stopping down the iso is rising, resulting in noisier images which look less sharp.

no, same at 160

 

Those lenses shouldn't get less sharp stopped down to f4 as far as I'm aware - could be wrong of course

[leicashot]

Also shallow depth of field can give the 'illusion' of a sharper image due to the more 'immediate' drop off of focus between sharp and unsharp.

 

Otherwise you're just not exposing correctly and should check that....not the camera, but yourself. Remeber a camera DOES NOT over/underexpose.....the photographer does.

[Double Negative]

Research "diffraction" and the effect. Though this generally doesn't start happening until maybe f/5.6-8 and down - and varies depending on medium/format as well.

 

Then there's the lens' sweet spot - sharpness increases from wide open and beyond it, gradually gets worse. That sweet spot varies with the lens but a general rule of thumb is "about two stops down from wide open." So an f/2.8 lens would be best at say, f/5.6 as an example.

[01af]

That sweet spot varies with the lens but a general rule of thumb is "about two stops down from wide open."

"Two steps down from full aperture" is just a myth. In fact, the sweet spot varies only very little for a given format. For most 35-mm-format lenses, it around f/8 .. f/11, no matter what the lens' speed is. For modern Leica lenses, it usually is around f/5.6—which means Leica lenses are better than the rest. The better the lens, the wider the sweet-spot aperture (for a given format).

 

For larger-format lenses the sweet spot tends to be at smaller apertures; for smaller-format lenses it's at wider apertures.

[Guest mc_k]

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You need to do a true resolution test, not a focus test. Shoot something like a page of magazine text head on...wide-open, and two or three stops down. "Bracket focus" by focusing where the rangefinder tells you, and also in a little neighborhood around there. This, to account for any focus shift. Take the best shot at each aperture, and you should definitely find equal or better resolution two or three stops down.

[jaapv]

Diffraction is the reason. The better the lens, the wider the aperture that it gets visible...

[zlatkob]

"Two steps down from full aperture" is just a myth. In fact, the sweet spot varies only very little for a given format. For most 35-mm-format lenses, it around f/8 .. f/11, no matter what the lens' speed is. For modern Leica lenses, it usually is around f/5.6—which means Leica lenses are better than the rest.

That's not just a Leica thing. According to the MTF charts at Photozone.de, many Canon and Nikon lenses peak at f/5.6.

[01af]

... many Canon and Nikon lenses peak at f/5.6.

Many? I'd say, the finest of them, yes, but not in general.

[zlatkob]

Well, they are not hard to find. Just check the MTF charts at Photozone.de -- even the cheap Canon 50/1.8 II, 50/1.4 and 50/2.5 macro all peak at f/5.6.

[01af]

Just check the MTF charts at Photozone.de—even the cheap Canon 50/1.8 II, 50/1.4 and 50/2.5 macro all peak at f/5.6.

MTF charts published by Photozone are hardly worth th electrons required to transmit them across the Internet. And then—do those lenses peak at f/5.6 at the frame's center, or overall?

[zlatkob]

MTF charts published by Photozone are hardly worth th electrons required to transmit them across the Internet. And then—do those lenses peak at f/5.6 at the frame's center, or overall?

What's wrong with Photozone's MTF charts? If you look at the charts, they will answer your question about center vs. overall. Many lenses peak at f/5.6 in both center and corners, including the inexpensive Canon 50/1.8, 50/2.5 and 35/2. The Canon 50/1.4 peaks at f/4 at center and f/5.6 at corners. The more expensive 35/1.4 peaks at f/2.8 at center and f/5.6 at corners. The Nikon charts show similar results. I'm sure Canon and Nikon make some clunker lenses, but the characteristic of peaking at f/5.6 is not a hallmark of being better than the rest.

[steinzeug]

In response to all the answers my issue still remains, irrelevant of individual optimum f-stops, if i take a cityscape/landscape wide open, sharpness in the area of focus is great, however take the same shot at lets say f16 and nothing is anywhere near as good, infact everything is more or less unsharp.

[jaapv]

And it will always be like that. Of course, the sharper the lens is wide open, the more you will notice. Other than that it will be the same with any lens, irrescpective of brand. A quote that puts it better than I could (cs.edu):

 

 

Can We Use the Smallest Aperture to Yield Greater Depth of Field?

Unfortunately, the answer is "no." As the light rays passing the lens tube and the diaphragm, some may be diffracted as shown in the figures below. If the diaphragm is large (i.e., a large aperture), because the proportion of the diffracted light and the non-diffracted light is so small and is negligible, diffraction does not contribute to the loss-of-quality very much. See the left figure below. However, when the diaphragm is small (i.e., a small aperture), the amount of light that can pass through the diaphragm is reduced and hence the proportion of the diffracted and non-diffracted light becomes significant. As a result, the quality of the image is also reduced. See the right figure below. Therefore, closing the diaphragm (i.e., using small apertures) all the way down to the smallest aperture may not increase the quality of an image. In general, the quality of a lens increases as diaphragm closes down. This improvement will reach certain point. After this, quality goes down because of the impact of diffraction. ]

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[jaapv]

And:

 

 

Diffraction - Wikipedia, the free encyclopedia

 

 

Scroll right down to "diffraction by a circular aperture"

[Yogibear]

"when i up the aperture to 4, 5.6 or higher" (Original post)

"however take the same shot at lets say f16" (Last post)

 

Now, what is it? f16 or f4?

[steinzeug]

Now, what is it? f16 or f4?

 

anything above 4 upwards and sharpness/details being to deteriorate

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Hallo,

Look here: Leica M

[jaapv]

Yes - that is normal.

[steinzeug]

Yes - that is normal.

 

so when would one use f16?

surely not for landscapes...