Pentax 645 legacy glass and metering on D800

Started May 19, 2012 | Discussions thread
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light_bulb Contributing Member • Posts: 835
Pentax 645 legacy glass and metering on D800

I have barely any experience with Nikon DSLR but had a D800 for a half day rent period yesterday in order to test some of my Pentax 645 glass on it. At the same time, I gave the Nikkor 85 1.8 G a try.

Unfortunately, I was unable to achieve consistent metering. I expected the camera to be able to notice that lenses are mounted which do not communicate with the camera and thus use the incoming light to calculate shutter speed in aperture priority mode. However this was not the case. While stopping down, shutter speed remained the same.

How can this be dealt with? I tried manual mode but that did not help.

Apart from the metering issue, my preliminary experience can be summed up as follows:

The 645 A 45 2.8 can deliver sharp results only in the centre of the frame while corner sharpness is relatively poor. This is a known issue with this lens. However I had expected it to be less pronounced with the smaller sensor. Depending on subject matter it can still be used. Manual focussing with the viewfinder is somewhat tricky.

The FA 645 75 2.8 delivered more consistent results accross the frame.

The FA 645 120 4.0 lives up to the expectation. However while tack sharp wide open on the Pentax 645D it is particularly tricky to manual focus precisely on the D800. Stopped down this is masked by greater dof and it delivers very sharp results.

The FA 300 4.0 was a surprise. Manual focussing worked very well and it can even be used handheld at 1/250 shutter speeds. Sharpness is very good and even wide open there are no visible abberations.

Most likely, I will repeat this test, once I know how to deal with the metering.

As a Nikon lens to compare the Pentax lenses with, I chose the Nikkor 85 1.8 G which - as far as I have read - has a very good reputation on the D800.

The AF mostly worked very well also under dim light. With close subject matter, the AF assist light was helpful.

This would be one of my favorite Nikkors on the D800. I was able to provoke some fringing wide open with strong lights in the background. However this is the sort of crash test that will make many fast lenses look faulty wide open.

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