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Harold Gough
Joined: 09 Mar 2008
Posts: 5736
Location: Reading, Berkshire, England
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 Posted: Sun Apr 29, 2012 12:01 pm Post subject: Shedding Light On Moss from Behind: A Flash Experiment |
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I have been having fun developing a way of using my film flash guns and TTL metering to take flash-lit images, with strictly-controlled exposure, using my digital camera. Essentially, the digital camera just opens and closes its shutter and captures the image lit and metered by the film camera/lens/flash combination.
If you want to follow the saga in detail look here:
http://www.photomacrography.net/forum/viewtopic.php?t=16626
As members not interested in technique might, however, like to see some of the images, representatives have been selected to be posted here.
During what might be the final main development phase of the project, back-lit images, done in about half an hour, excluding processing, one of the images turned out surprisingly pleasing. It was life size (1:1) on the sensor, the crop factor doubling that to 2:1. It was slightly cropped for composition. Blue background:
For the whole backlit exercise see here:
http://www.photomacrography.net/forum/viewtopic.php?p=107593#107593
Understanding of why it worked might require reference to more of the topic.
Anyway, this indicates more the kind of effect I wanted but there is much refining of the method to be done:
This is well on the way to the kind of result I wanted. Matt Black background:
Hardware used:
For the flash and flash metering: Olympus OM4 body, Tamron Adaptall-2 90mm f2.5 macro (MF), ISO 400 f2.5 aperture priority, Olympus T-32 flash on TTL OTF chord, both hand-held
For the image capture: Olympus m4/3 E-P2, Leitz Wetzlar Elmarit-R 60mm f2.6 macro (MF, operating fully manually), shutter priority, 1.6 seconds open flash, ISO 100 f11, tripod.
I have not attempted to identify the mosses, which appear to represent two species, probably in different genera.
Harold
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Happiness is having the right adapter.
My manual flash setup for high magnification:
http://www.photomacrography.net/forum/viewtopic.php?p=117843#117843
Last edited by Harold Gough on Sun Apr 29, 2012 12:55 pm; edited 2 times in total |
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johan
Joined: 06 Sep 2011
Posts: 504
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| Posted: Sun Apr 29, 2012 12:30 pm Post subject: |
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That's really neat Harold! Nell worth perservering with the experimentation. I never thought I'd see moss as beautiful but actually these show a very neat different side to it!
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Harold Gough
Joined: 09 Mar 2008
Posts: 5736
Location: Reading, Berkshire, England
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| Posted: Sun Apr 29, 2012 12:38 pm Post subject: |
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Thanks, Johan.
I was only trying to get the exposure right, with enough of the subject in focus to make an image worth posting in the original topic. The way this one turned out was a real bonus.
Harold
_________________
Happiness is having the right adapter.
My manual flash setup for high magnification:
http://www.photomacrography.net/forum/viewtopic.php?p=117843#117843 |
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PanoGuy
Joined: 15 Mar 2010
Posts: 27
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| Posted: Wed May 02, 2012 7:10 am Post subject: |
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I really like the 2nd image with the dark background.
Have you experimented with cross-polarization? That would let you eliminate a lot of the direct reflections from the flash (or adjust them to taste). |
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Harold Gough
Joined: 09 Mar 2008
Posts: 5736
Location: Reading, Berkshire, England
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| Posted: Wed May 02, 2012 7:21 am Post subject: |
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| PanoGuy wrote: | I really like the 2nd image with the dark background.
Have you experimented with cross-polarization? That would let you eliminate a lot of the direct reflections from the flash (or adjust them to taste). |
Thanks, PanoGuy.
Yes, the second image was one type of effect in a range which I can't even visualise. I just wanted to be able to make some kind of presentable, back-lit images in terms of methiod development.
I am aware of cross-polarisation and have provison for using it with one of my ring flashes or over light sources. There are far too many variables already involved to want to add that complication generally as this stage. Of course, any kind of polarised light control work well only with flat surfaces. I have a subject I was planning to photograph this week that would be ideal to try it on, as a one-off. Thanks for the nudge.
Harold
_________________
Happiness is having the right adapter.
My manual flash setup for high magnification:
http://www.photomacrography.net/forum/viewtopic.php?p=117843#117843 |
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DQE
Joined: 08 Jul 2008
Posts: 1441
Location: near Portland, Maine, USA
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| Posted: Wed May 02, 2012 9:43 am Post subject: |
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Thanks for posting these - we have a lot of qualitatively similar mosses in our yard (by our preferences, we don't fertilize the law and enjoy letting it grow semi-naturally). Yet I had not thought of these plants as being candidates for macro until you posted your recent series.
Just to be sure I'm following the basics - about how large is the field of view in the above photos? I estimate that it's about 20-25mm but am unsure.
Also, what technique did you use to create the blue background? is it simply a piece of blue paper?
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Only 2 more weeks until our bushes and trees leaf out in Maine where I live!! We're still going below freezing at night, though, so most flowers can't cope...
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"Diffraction never sleeps" |
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rjlittlefield
Site Admin
Joined: 01 Aug 2006
Posts: 12582
Location: Richland, Washington State, USA
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| Posted: Wed May 02, 2012 9:49 am Post subject: |
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| Harold Gough wrote: | | Of course, any kind of polarised light control work well only with flat surfaces. |
Not sure exactly what you're thinking of here. It's true that putting a polarizing filter on just the lens only works with surfaces at specific angles. But cross-polarized, with filters on both the lights and the lens, works great on curved surfaces too. See for example the article by Hershberger.
--Rik |
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Harold Gough
Joined: 09 Mar 2008
Posts: 5736
Location: Reading, Berkshire, England
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| Posted: Wed May 02, 2012 10:23 am Post subject: |
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| rjlittlefield wrote: | | Harold Gough wrote: | | Of course, any kind of polarised light control work well only with flat surfaces. |
Not sure exactly what you're thinking of here. It's true that putting a polarizing filter on just the lens only works with surfaces at specific angles. But cross-polarized, with filters on both the lights and the lens, works great on curved surfaces too. See for example the article by Hershberger. |
Rik,
Thanks, but I'm not convinced by the article in this context (although I am open to further evidence). Surfaces in the article are fairly flat. Certainly, in everyday use (polarized light source the sun) of a polarizer to moderate reflections from glass or from water, the best control of the polarized light is when the polarizer is at a particular angle, which I understand to be the angle of reflection, equal to the angle of incidence (from the sun). Other reflections, which must involve polarized light from the sun, are rarely well controlled.
In cross-polarisation the polarised light may be produced from a flash light at any angle relative to the axis of the lens, or may be parallel, as in the ringflash arrangement, where the two polarizers are concentric. I suspect that there may be different considerations for cylindrical objects than for spherical ones, to take two simple examples, but I am rapidly getting out of my depth here. I have not used cross-polarization so I cannot base what I say on experience. The question seems to be whether the shape of a surface can change the plane of polarisation or just the direction of travel of the light.
Before anyone suggests that polarizer deals only with reflections on shiny surfaces, the use of a polarizer is a well-established means of intensifying colours e.g. of the sunlit walls of painted buildings.
Harold
_________________
Happiness is having the right adapter.
My manual flash setup for high magnification:
http://www.photomacrography.net/forum/viewtopic.php?p=117843#117843 |
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rjlittlefield
Site Admin
Joined: 01 Aug 2006
Posts: 12582
Location: Richland, Washington State, USA
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| Posted: Wed May 02, 2012 10:49 am Post subject: |
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| Harold Gough wrote: | | Thanks, but I'm not convinced by the article in this context (although I am open to further evidence). |
In that case, you might be more interested in my own article HERE.
--Rik |
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Harold Gough
Joined: 09 Mar 2008
Posts: 5736
Location: Reading, Berkshire, England
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| Posted: Wed May 02, 2012 11:22 am Post subject: |
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| rjlittlefield wrote: | | Harold Gough wrote: | | Thanks, but I'm not convinced by the article in this context (although I am open to further evidence). |
In that case, you might be more interested in my own article HERE. |
Rik,
I'm so glad that I was not convinced, as I would have missed your superb article. I now understand why a polarizer intensifies the sunlit colours of coloured buildings. It removes the dilution from specular white light.
Of course it is Brewsters Angle (that I don't think I have seen named before, but I have forgotten so much, about everything  ) that I was unsure was the conventional angle of reflection.
I now understand how the glued-together cross-polarizer filter assembly I have will work. (I obtained it after I put aside film for much of last year to get to grips with digital). So I should be able to give it a run with a subject liable to give all sorts of specular and other reflections. That will stay under wraps until the studio session. I am going to have to use a (ring) flash of a quarter of the power of the one I have been using so far, although it will be closer to the subject but there will be considerable light loss from the filters. I may use a flash meter for the first time to determine initial settings.
Harold
_________________
Happiness is having the right adapter.
My manual flash setup for high magnification:
http://www.photomacrography.net/forum/viewtopic.php?p=117843#117843 |
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DQE
Joined: 08 Jul 2008
Posts: 1441
Location: near Portland, Maine, USA
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