Inside the Forest
A few years ago, I was taking photographs with a 4x5 view camera. One of these.
Some of the lenses I was using for that camera also work with my medium format Phase One digital back. So I have been testing my lenses in a mini optical lab that I put together. It’s not much: camera on a tripod, looking at a high-resolution test chart. The chart looks like this (image taken with the same lens I used for the forest photograph above):
I load the picture of the test chart into software that looks at those diagonal lines and calculates the sharpness of the edges. This is called “MTF” which is short for Modulation Transfer Function. Still not clear? In simpler terms, it’s a measure of how well the image contrast holds up for small details. A sharp image will of course show smaller details than a fuzzy one. The chart image is pretty much dead sharp, and the forest image is very sharp as well.
I am using the tests to decide which of these old lenses to keep, and which ones to sell. This one, a Nikon 90mm f/8, is a definite keeper.
These old lenses see much a wider area than I can record with the medium format digital back, so my camera includes the ability to slide the lens around to get pictures that are outside the central frame. Here’s a three-frame panorama taken with the Nikon 90mm lens, stitched together in Capture One software. The shots were taken by sliding the lens 15mm left of center, center, and 15mm right of center.
You may have to widen your browser window to see the whole shot.
The funny part of this is that I have had this lens for years, and had never used it even one time. I had another 90mm lens that was supposed to be sharper. Oops. This Nikon lens is one of the sharpest I have! A fun discovery, for sure.
Here’s another photo taken with the Nikon 90mm.
All of these images were taken in a small park in Bonney Lake, WA, accessible at the back of the Fred Meyer parking lot. It’s a fun discovery.