Originally posted by travelswsage I am using my first k lens without an A setting -- the k28 3.5 on the the k-1 and my exposures using the green button are continually 2 to 2 1/2 stops overexposed.
This behavior has a long history and is frequently touched on in discussions on this site. Here are the pertinent bullet points. Read them and weep (or not):
- Stop down metering (both green button and manual aperture in Av mode) is inherently unreliable on your K-1. Metered exposure is often close enough, but not predictably so.
- This is a pervasive problem with AF SLR cameras across brands
- The cause is related to loss of light at the main mirror for the PDAF sensor coupled with focus screen optimization to compensate for the light loss. The metered reading is skewed to accommodate the screen quirks. This approach only works properly with open aperture metering when the camera "knows" the maximum aperture and when the body controls the aperture stop-down.
- The effect is that meter response is not consistent or fully linear at all apertures and varies by lens. Because of this, dialing in exposure compensation may or may not be a reasonable solution.
- The problem was much worse on bodies earlier than the K-7
- My experience has been that metering with most lenses is essentially accurate and linear between at apertures narrower than about f/4
- The above point fails as light levels fall and apertures become narrow. The hidden gotcha with stop-down metering is that light to the meter may easily fall below the lower limits of meter sensitivity as one stops down. Gross underexposure is the result.*
- My experience on the K-3 has been that M mode with green button or DOF preview is more reliable than Av mode, even with manual aperture on M42 lenses. Whether this is true on the K-1, I don't know.
So, what to do? Here is my flow:
- Use M mode
- Set aperture
- Do an initial green button or DOF preview reading. For tricky lighting a gray card may be useful.
- Make test exposure and adjust shutter speed to center the histogram
- Shoot using these settings until either the subject or light changes
Don't sweat the fact that there is no real time metering of the subject. If you must, use Av mode and EC, but my experience has been that ability is highly overrated. I have found that a hand-held light meter using traditional technique is incredibly useful when working with vintage lenses and for many subjects will outperform the camera's evaluative metering when used skillfully.
Steve
* This is a long-standing issue with stop-down meter bodies at some EVs. Spotmatic models actually have a feature where there is a red flag visible through a small window for certain combinations of ASA (ISO) and shutter speed. The was also a table of valid exposure settings included in the user manual.