mifho said:
That really doesn't matter as far as focusing in low light. If the light isn't there, doesn't matter what type of AF sensor because it's not going to work.
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How does max lens aperture affect low light autofocus?
- Thread starter drmikeinpdx
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That really doesn't matter as far as focusing in low light. If the light isn't there, doesn't matter what type of AF sensor because it's not going to work.
Quick and dirty low light focus test
OK, I took my 5D3 and four lenses into my studio and reduced the ambient light to the point that the lenses were just barely able to focus. I varied the light a little bit to sort of bracket the point at which each lens would begin to focus.
I aimed each lens at my usual focus grid target placed flat on the floor. The grid is essentially a ~ 3x5 foot piece of white graph paper with 1 inch squares. It is actually a cardboard layout mat for sewing projects. The focus point consisted of a 12 inch length of black tape across the center of the grid so it was a fairly high contrast target. I stood about ten feet from the focus point and aimed down at about a 30 degree angle. This is the setup I use for MFA, although I normally let the camera have a lot more light to focus.
The actual exposure was made with a strobe to eliminate camera shake.
My results:
24-105 F/4: needed the most light to focus, but focused accurately when focus lock was achieved. The target appeared dim in the viewfinder and it was sometimes hard to find the black tape focus target.
Tamron 28-75 F/2.8: needed moderate light to focus, accuracy was acceptable, but not as precise as the Canon lenses.
Canon 40mm F2/8: needed moderate light to focus, but very good accuracy
Canon 85mm F/1.8: needed the least amount of light to focus and had extremely good accuracy.
As always, your mileage will certainly vary!
OK, I took my 5D3 and four lenses into my studio and reduced the ambient light to the point that the lenses were just barely able to focus. I varied the light a little bit to sort of bracket the point at which each lens would begin to focus.
I aimed each lens at my usual focus grid target placed flat on the floor. The grid is essentially a ~ 3x5 foot piece of white graph paper with 1 inch squares. It is actually a cardboard layout mat for sewing projects. The focus point consisted of a 12 inch length of black tape across the center of the grid so it was a fairly high contrast target. I stood about ten feet from the focus point and aimed down at about a 30 degree angle. This is the setup I use for MFA, although I normally let the camera have a lot more light to focus.
The actual exposure was made with a strobe to eliminate camera shake.
My results:
24-105 F/4: needed the most light to focus, but focused accurately when focus lock was achieved. The target appeared dim in the viewfinder and it was sometimes hard to find the black tape focus target.
Tamron 28-75 F/2.8: needed moderate light to focus, accuracy was acceptable, but not as precise as the Canon lenses.
Canon 40mm F2/8: needed moderate light to focus, but very good accuracy
Canon 85mm F/1.8: needed the least amount of light to focus and had extremely good accuracy.
As always, your mileage will certainly vary!
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