Inaccurate Aperture Markings on Meike 28/2.8

Started 2 months ago | Discussions thread
kypfer Regular Member • Posts: 497
Re: Inaccurate Aperture Markings on Meike 28/2.8

Schleiermacher wrote:

Thanks for weighing in and asking for clarification.

The Meike 28/2.8 is a native x-mount lens mounted to my x-t20. It’s aperture blades open and close smoothly and responsively as I turn the ring (not sticky).

The Pentax M28/3.5 lens was also mounted to the x-t20 using a trustworthy K&F Concepts adapter that works fine for all my adapted Pentax lenses on the x-t20.

I own a Pentax body and can compare metering result with the M28/3.5 on it against results on the x-t20 to verify consistency.

But even setting aside the comparison with the Pentax, the amount of light coming through the Meike lens at each of its printed stops on the aperture ring is not a standard 1 stop of actual difference. When you move from F/8 to F/11 on the Meike dial, for example. the shutter speed only changes from 1/60s to 1/50s. You’ve got to set it nearly F/16 on the dial to achieve shutterspeed of 1/30s.

My test results are consistent with those of another tester on the Fred Miranda forum who came away with nearly identical results to mine when he tested with a handheld meter.

The only factor that I can think of that may be in play is the vignetting of the lens. The Meike vignettes a full stop at 2.8 and gradually improves until F/8. I’m wondering if whatever is producing thr vignetting is also altering the light hitting the meter and interfering with the standard 1-stop differential you’d expect from each full stop change on the aperture dial.

Matt

It certainly sounds like the Meike isn't working properly. Unfortunately you're posting here on a Pentax forum and as the Meike isn't available in PK mount you're only likely to get a bit of theoretical "try this try that" response. Probably best find a user group for your camera where you're more likely to find someone with first-hand experience.

At the end of the day, does it really matter if the readings on the dial are wrong, provided the pictures are correctly exposed according to the camera's meter?

Good luck

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