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Surprisingly bad lens, Batis 40mm f/2 CF

Started Nov 28, 2021 | Discussions thread
AeroPhotographer Regular Member • Posts: 461
Re: Surprisingly bad lens, Batis 40mm f/2 CF

I did some more tests on the close focus issue and remain happy with my Batis 40mm.

I photographed a page of text obliquely at about a 45 degree angle. I had to select the smallest focus area box to insure that I was focusing on only one line of text. Each shot I moved the camera in and out until I was just barely into the AF range, where the focus box turns green when in focus. I also used flash to freeze shake. I shot at f2 and f2.8 and all shots were perfectly focused on the chosen line of text.

I focused on "Autofocus"

It occurred to me that people encountering focus problems may not have realized how shallow the depth of field is at 0.3x magnification, so I calculated it with the formula

DOF in mm = .02 * f# * (1+M) / M^2 M=magnification

Here are the results (all for magnification = 0.3x)

f#     DOF

f2 = 0.58mm

f2.8 = 0.81mm

f4 = 1.16mm

f5.6 = 1.62mm

f8 = 2.31mm

f11 = 3.18mm

f16 = 4.62mm

I focused on the brown anthers

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