I took this photo today with my K-1, an MC4 x2 teleconverter and a Sigma 50-500mm lens (set at 400mm). It actually came out significantly better than the Sigma without the TC (enlarged to the same scale) so I was impressed with the performance of the teleconverter.
For those interested, I used a Thousand Oaks "SolarLite" film solar filter, the lens set at f11(manually using the lens f-stop ring since the lens was decoupled from the camera), 1/250s exposure at ISO 800. I used a tripod, 12s shutter delay, and Liveview with electronic shutter. The image is a DNG, adjusted in RAWTherapee and Photoshop.
I think I was lucky with the focus (manually done with the lens) because of a problem I encountered with Liveview (read on).
I had previously used Liveview with just the lens and focused on the set of sunspots using the magnified Liveview image. The sunspots gave me a good focusing reference. Although the Liveview image appeared sharp, some sharpness disappeared when the actual image was captured and examined in review mode - I attributed this the focus peaking used in Liveview as it make the enlarged Liveview image sharpen up a bit.
When I attached the 2x TC, the camera apparently didn't know what f-stop was being used, and the image washed out so much, the sunspots disappeared (and the sun's image was super bright). I tried blocking the lens aperture and closing it down, but the camera compensates and the image just get noisier (due to less light) but stays so bright it still washes out the sunspots (tried darkening the LCD also and that didn't work either)? I finally used focus peaking and focused on the edges of the sun which was the only sharp reference left. That's where I think luck came in because the captured image was about as sharp as I could hope for, but having the spots is a lot more reliable. It may be a foible of the AE system since with the TC, the sun fills more of the image than with the 400mm lens (and there's the totally black background). I had the K-1 set to spot metering for both cases (though I thought that would be irrelevant since I was in manual mode).
Is there any way to bring the image back down in brightness with the decoupled lens (due to the 2x TC) so I can see the sunspots for a focusing reference?
Note in this image, solar granulation can be seen as well as limb darkening (darkening at the edges of the sun due to the "horizon" of the sun and the surface angle relative to the viewer). The sun is pretty much clear right now other than these few spots so the corona this Monday should be rather bland compared to its appearance when the sun is more active. I also attached the uncropped K-1 frame for reference (approximately 800mm equivalent focal length - though not to full K-1 resolution, of course).
Anyway, if someone knows how to tame the K-1 Liveview gain, let me know. Thanks.
Last edited by Bob 256; 08-18-2017 at 09:03 PM.