16 Unique Features That Your Camera Probably Doesn't Have

Started 3 months ago | Discussions thread
Guy Parsons
Guy Parsons Forum Pro • Posts: 36,892
Re: Telecentric .... or not.

Guy Parsons wrote:

I am sure that my bunch of old 4/3 lenses stored somewhere are a mix of possibly "telecentric" and impossible to be "telecentric" lenses, due to that rear element measurement.

So it was mainly to do with marketing - the reliable source of most baloney in any industry.

When the sun comes up here in Oz I will look through a few of the old 4/3 lenses to see how they obey the test stated in Wiki as "Image-space telecentric lenses have an exit pupil infinitely far in front of the lens; that is, if one looks in the back of the lens, the image of the aperture is very far away." I'll try to remember to report back on that.

Back again after looking at my old 4/3 lenses.

Lens.................Rear element approx........telecentric (as per view test above)

50/2 macro................23mm.....No, but a very mild effect of aperture seems further away.

35/3.5 macro..............15mm................................No

14-54/2.8-3.5...............19mm.........................No, but very very mild effect like the 50mm

11-22/2.8-3.5................19mm..............................No

14-45/3.5-5.6.................18mm.............................No

40-150/3.5-4.5................21mm.......................No, but very very mild effect like the 50mm

40-150/4-5.6......................13mm...........................No

The last lens came with a very early E-PL1 kit and with the MMF-2 to adapt it to the E-PL1. The rear element needs to be about 22mm or bigger to allow any chance of true image side telecentricity.

So nothing there that leads me to believe that "telecentricity" was a global design feature in the 4/3 lens range. The very mild effect noted on some of the lenses made the aperture look as though it was slightly further inside the lens than where I expected it to be, but certainly not distant as the Wiki page test indicated.

Summary: As usual, the telecentric issue was 99.99% baloney from the marketing people, and people believed it without testing if it was true.

To get the aperture visible, I set the A mode to f/5.6, set a button to DOF preview, then held down the button while removing the lens keeping the camera turned on. That way the aperture stays at f/5.6 on the removed lens and makes it easier to do the view test. No damage happens as pressing the lens release always disconnects power from the lens.

 Guy Parsons's gear list:Guy Parsons's gear list
Sony RX100 VI Olympus PEN E-PL1 Olympus PEN E-PL5 Olympus PEN E-P5 Olympus OM-D E-M10 II +10 more
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