**Weekly MF Forum Photo Thread 14 Apr - 20 Apr**

Started 8 months ago | Discussions thread
Rick Knepper
Rick Knepper Forum Pro • Posts: 16,330
Re: Flora in Caprock Canyons State Park, Tejas

JimKasson wrote:

Rick Knepper wrote:

First time shooting with the 120mm macro.

Turning the lens outward. Foreground is about 2-300 yards away but I am conflicted about the performance at infinity.

Looks to me like atmospheric effects. Sun had been up for a while, I'll bet.

Probably is. The wind was blowing hard and some of that might be dust.

The 120 performs well at infinity, though not quite as well as the 110:


Actually, it was this comparison that convinced me to go with the 120mm first. I saw little difference between the two at this distance. The fact that I'd get double duty from the 120 tipped the scales. I'm going to own all of the lenses for this system, just a matter of when.

At f/13, we're looking mostly at diffraction with either of those lenses, if the air is still and there are no whatever the air equivalent of a thermocline is.

F13 is a strange choice but I had just finished shooting macros where I intended to use the aperture. This is my first use of this lens so I am still not totally dialed in to the best aperture for "across the frame" focus.

Remind me. For DoF purposes, f13 on this system is equivalent to approx. f10 on FF. Does this factor apply to diffraction too?


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