I got overexposure problem with Nikon 300mm f/4 lens.

When I use this lens, the camera poorly handles exposure level of images at infinity distance.

Here is what I found about overexposure problem in manual lens.

Paul Holman says:

The metering doesn’t work properly when the iris is set to low values eg f11, 16, 22 on manual iris lenses.

You can see this by setting the camera to AV then taking a set of shots from f2.8 – 22. In theory each shot should be the same, but in practice as the aperture is closed down the camera misreads the light coming in and progressively underexposes.
It’s down to the shape of the light cone the lens projects backwards towards the sensor and the positioning of the exposure reading cells.

With an auto iris lens it’s not an issue as the camera is always metering off the fully open lens, it only happens with manual iris lenses.

You can also see a similar effect when using the Canon tilt and shift lenses. As the lens displacement increases metering accuracy falls off significantly.

I’m afraid you just have to live with it and accommodate it. It’s another one of the small penalties of using such a low tech lens, although in optical quality it’s absolutely remarkable value for money.
Posted 2 weeks ago. (permalink)

Date/Time : 2012:07:21 18:14:42
Resolution : 3906 x 2602
Exposure time: 0.040 s (1/25)
ISO equiv. : 100
Whitebalance : Manual
Metering Mode: pattern
Exposure : aperture priority (semi-auto)


ufraw shows 0.8% of overexposure. I applied [Colors]-[Levels] using GIMP. The value I chose was black 105, gamma 0.52, white 255. The histogram shows too much white data.

The overexposure corrected by GIMP

About janpenguin

Email: k2.mountain [at] gmail [dot] com Every content on the blog is made by Free and Open Source Software in GNU/Linux.
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