Posted 17 March 2013 - 06:08 AM
Years ago I had the habit of shooting 60 minutes at f/4, with E200 pushed 2 stops. They often suffered from vignetting, severe sky glow and blown highlights in bright nebulae. Once corrected they made decent images, but at a cost of good color and were overly contrasty.
E200 is a low/medium contrast film and this is an asset when shooting a high contrast subject. Pushing +1 (ISO 320) increases effective speed by 2/3 stop and also increases saturation, but with only modest increase in contrast and little if any additional grain.
A two stop push (ISO 640)dramatically increases recording power for faint nebulae, markedly increases contrast and grain but weakens color saturation if slightly overexposed as was the case with many of my works in 2008. I was trying too hard to capture impossible detail and paid the price. Salvageable, but not ideal images were the result.
I've settled on a 1.5 push (ISO 480) and a 30 minute to 45 minute exposure at f/4.8 (the 105 and 165 lenses)or 45-75 minute exposures at f/5.6 (200 and 300 lenses). Longer exposures can be had if conditions allow of course.
These exposures allow me to capture as much detail as possible within a reasonable exposure time. Your 55 minute at f/5.6 fits within this domain and should do well.
Your skies offer very good potential, as we have seen great results from your location. No place is ideal as we all have to deal with aircraft, fireflies, and satellites. My south horizon looks directly into the Northeast Corridor for aircraft flights on the east coast to Europe. You got to look sharp and know where your framing!
A note on stopping down. Some prefer to shoot lenses wide open and correct later in post processing the resulting vignetting. I prefer to stop down, which does several things. It allows longer exposure, therefore producing better contrast for the subject, a deeper limiting magnitude , and a flat field requiring less work in post processing. The Pentax line of fine lenses produce sharp stars over the frame wide-open, but are improved by stopping down as well.
As for the above frame. I am pleased with it, but there is always room for improvement. I am also becoming more of a fan of shooting B&W which allows more control of contrast and renders finer star images as you will see in my next posting.
My best lenses, the 165 and 200 are practically without peer and will be my primary lenses this year. Medium format provided the level of quality unsurpassed by 35mm and much of today's modern DSLR's in wide-field work. The limiting factor is scanning, which when done on cheap scanners does a mediocre job, but tolerable until something better comes along.
Enjoy the film while it lasts. The stock of E200 in my freezer is still good. I'll shoot it as long as I can.