Is lens testing at chart distance really an accurate measure?

Started 2 months ago | Discussions thread
Bernard Delley Senior Member • Posts: 1,490
Re: exhaustive testing becomes -- exhaustive
4

of course MTF depends, a little, on imaging ratio, or object distance. One needs a different chart for each imaging ratio, if the full chart is to be used.

I guess for a 'normal' indoors test station, it gets hard to go beyond a chart 2.4 x 3.6 m sized, giving a 1:100 imaging ratio onto the 24x36mm format. A DIN A0 size chart gets imaging ratio 1:33 for the same format. To fill the FX frame with a 800mm tele-lens you need a test hall exceeding 28m in length from the A0 chart ~ possible.

A test stand for 1:77 imaging with wide and normal lenses.

There are also Huge outdoors charts ! for aerial or satellite optics testing.

Maybe, somebody will do MTF testing, using buildings some day. There may be suitable buildings.

For closeup MTF testing, one may use razor blades.

Optical bench apparatus have a collimated test target. Infinity testing is the standard. For finite distance testing one needs a different collimator for each distance.

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