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Fun with MF images - ARCHIVED - FOR VIEWING ONLY

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WildRover

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One of my few attempts at shooting bokeh. I actually gave up on this in the field. Three shots but not a real plan. First one at f/22. Ugly bokeh. Next was at f/4. Great bokeh, no depth of field. Then I changed composition slightly and f/4 with a small focus shift. A breeze picked up and I packed up thinking I didn't get anything. After reviewing in Lightroom I decided to put the three through Zerene Stacker. After some PP in photoshop, I'm surprised and happy with how this turned out.

Pentax 645D, 120A, cropped a bit.

I'm no plant expert. Identified this with some googling, but it could be labeled wrong. This was a wild growing shrub along Lake Michigan in Door County, Wisconsin. If anybody thinks its something else, please let me know.

Rick

 
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WildRover

Member
Thanks for the reply and compliment Bill. Too bad it's an "escapee". I like to promote wildness and a "pure" nature with my photographs. Oh well. It was a nice little exercise nonetheless. It reminds me of a some notecards I self published some years ago - before the wonders of the internet. One of the photos had some flowers in it that I simply labeled as wildflowers as part of the photo's description. It was later pointed out to me that it was a common bulb flower that was a remnant from an old farmhouse that was once there. The photo was from a state park and the farmland had been acquired when the park was formed.

Once again, thanks.

Rick
 

ondebanks

Member
With only a few exceptions (Phase One P+ Kodak sensors, IQ260), MF CCD backs in general, and especially older ones like my Kodak DCS645M, have truly awful long exposure dark noise, which corrodes image quality even with automatic dark-frame subtraction engaged.

So what do you do in enforced low-light long exposures, when the signal is only trickling in while the noise is building up to ridiculous levels? Mod your system to build the signal up to ridiculous levels as well! Admitting all the near infrared spectrum boosts signal by a large multiple in a Kodak CCD. All I have to do with my DCS645M is click off the removable IR-block filter.

In practice, the small focus shift due to IR wavelengths now dominating seems to cancel out the small focus shift due to removing the glass filter from the front of the DB.

So here's the Teapot and the summer Milky Way in Visible + IR [predominantly IR]. This reminds me of old hypered Tech Pan shots with a deep red filter, except here it's actually in colour: the little nebulae are reddish due to the 656 nm Hydrogen line. The star-clouds and interstellar dust clouds are more structured in IR than they would be in the visible.


Mamiya 645AFD, Kodak DCS645M unfiltered, 80/1.9 at f2.8. 12 x 1 minute exposures on an AstroTrac mount, processed in Deep Sky Stacker.


Including some foreground (the French campsite where we were staying) also leads to interesting results:

1 minute exposure, 45/2.8 S lens.

Ray
 

malmac

Member


Will

Carrying on, sort of from your beautiful tree - this is a small dead tree, bleached white by the sun, laying on a bed of green moss in a sub alpine area. I was inclined to turn this into an organic Rorschach ink blot image.

The drum roll sound effect - "and what do you see in the ink blot?"

Thanks for viewing.


Mal
 

gerald.d

Well-known member
With only a few exceptions (Phase One P+ Kodak sensors, IQ260), MF CCD backs in general, and especially older ones like my Kodak DCS645M, have truly awful long exposure dark noise, which corrodes image quality even with automatic dark-frame subtraction engaged.

So what do you do in enforced low-light long exposures, when the signal is only trickling in while the noise is building up to ridiculous levels? Mod your system to build the signal up to ridiculous levels as well! Admitting all the near infrared spectrum boosts signal by a large multiple in a Kodak CCD. All I have to do with my DCS645M is click off the removable IR-block filter.

In practice, the small focus shift due to IR wavelengths now dominating seems to cancel out the small focus shift due to removing the glass filter from the front of the DB.

So here's the Teapot and the summer Milky Way in Visible + IR [predominantly IR]. This reminds me of old hypered Tech Pan shots with a deep red filter, except here it's actually in colour: the little nebulae are reddish due to the 656 nm Hydrogen line. The star-clouds and interstellar dust clouds are more structured in IR than they would be in the visible.

Ray
Wow.

Ray - I'm very intrigued by your comment about the images being predominantly in the IR. I've not really done any astrophotography but the bug is nibbling me.

Would I get decent results with an Achromatic+ with a Heliopan IR780 do you think?

I'm probably going to get out into the desert this weekend and have another play with the Sony A7s, and perhaps I should take the Achromatic+ along with me also?

Kind regards,


Gerald.
 

ondebanks

Member
Wow.

Ray - I'm very intrigued by your comment about the images being predominantly in the IR. I've not really done any astrophotography but the bug is nibbling me.

Would I get decent results with an Achromatic+ with a Heliopan IR780 do you think?

I'm probably going to get out into the desert this weekend and have another play with the Sony A7s, and perhaps I should take the Achromatic+ along with me also?

Kind regards,


Gerald.
Hi Gerald,

Glad that you are impressed with my results!

Yes, your Achromatic+ would be an excellent choice for this type of thing. The only thing that would beat it is a dedicated cooled astro CCD of the same size, but they can only be used tethered.

My images are predominantly recorded in the IR because of the spectral response of Kodak's CFA on the CCD. In the visible, you get the usual 1 red, 1 blue, 2 green pixels for each block of 4. So the net sensitivity in red or blue is 25% of what it could be, and 50% in green. Then comes the transition region from visible to IR, between about 650 - 800 nm, where the red pixels still record strongly, while the sensitivity of the green and blue pixels starts to climb again. The IR-block filters on regular backs/cameras transmit almost nothing in that region, so it's a further addition of signal in my case. Finally, in the real IR, past about 800nm, the CFA filters become transparent and every pixel responds equally. This is like quadrupling the sensitivity to that part of the spectrum. In effect, just for those IR wavelengths, I have a cheap Achromatic back with equal light sensitivity to your Achromatic+.

But your Achromatic+ smokes it in two respects -
1) Far lower long exposure dark noise, thanks to the eXpose+ tech
2) Far higher visible light sensitivity (all pixels pick up all wavelenghts; no CFA losses), and somewhat higher in the transition region between about 650 - 800 nm.
Plus it's a 33% bigger sensor and it has unlimited exposure time (mine has a hard 1 minute limit).

With a full-spectrum Achromatic camera, you can do things like sequential tricolour imaging with 3 colour filters of your own choice, anywhere in the visible and/or IR; or no filter at all. Narrowband filters centred on nebula emission lines give fascinating and beautiful results. See e.g. Richard Crisp's work - Welcome to narrowbandimaging.com

Using a red or IR filter like your IR780 does give you a somewhat different view of astronomical objects. The Milky Way is a good target, because its brightest regions consist of mainly older, redder stars which emit more IR; and because all those interstellar dust clouds absorb and scatter light proportional to its wavelength (UV and blue suffers the worst losses, IR the least), so dusty areas of the galaxy look brighter in IR.

You should definitely give it a shot!

Ray
 

MARKC

Member
Still need to waiting couples months for red leaves there. :ROTFL:



"小"九寨沟 in southern China.

ALPA / HASS V / LEICA S & M / PHASEONE IQ & P+
 
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