Most of us know the lenses are good at certain aperture. Instead of blindly choosing to shoot at f/8 or f/11, wanted to quantity what is ideal f-stops for the two lenses. (Panasonic 35-100mm f/2.8 and Nikkor 24-120mm f/4).
Though I did the test for quite a few lenses, not as identical test as this, but the results are very similar.
I usually shoot only at full stops f/1.4 , f/2, f/2.8 , f/4, f/5.6, f/8, f/11 , f/16 and f/22. May be the habit I carried from the manual Nikkor D lenses, it also keeps the guess work simpler.
There are times when we have to shoot at the widest aperture for low light, or to have shallow DoF, or at the smallest aperture to reduce out of focus areas in the image or to get long exposure in bright light. This is just general rule I follow if I can choose between different f-stops.
What I found is most of the lenses are at their best from one stop above the widest aperture to two stops below the smallest aperture.
So f/4 – f/22 lens is at its best from f/5.6 to f/11
and f/2.8 – f/22 lens is at its best from f/4 to f/11.
The degradation of image quality is based on the quality of the lens. It’s hardly noticeable even at 100% view in an expensive lens to a huge difference of very soft image while viewing in a iPhone resolution of full image.
1) Panasonic 35-100mm f/2.8 lens
The image is sharp from f/2.8 all the way up to f/11. And best from f/4 to f/8.
Near the edge..
Sharp from f/5.6 all the way up to f/11. I omitted f/2.8 and f/4 as the the edges are in the out focus area.
2) Nikkor 24-120mm f/4
This photo is shot at well lit sunlight, with steady tripod.
This lens does really good job at f/8 and f/5.6, hardly noticeable difference at f/11. Would avoid f/16 and forget f/22 exists in the lens. If possible stay away from f/4 as well. The problem is D810 and its great sensor is looking for information the lens can’t simply provide.
Here are the full quality images.