My offical site is here: http://www.ki.tng.de/~sgude/
mare tranquilitatis
--- click the pictures to enlarge them in a separate window ----Nothing spectacular, just water and stones:
A camera obscura would be nice at this moment.
....or a camera with more than 8 seconds of exposure!
My new filter helped in this case: ND4, factor 10000, 13 steps (aperture)
...and combining 4 pictures helped me with long exposures: 24sec. eff. - last picture
The choices of filters are shown at the end of this page
Blurring the motion
These lenses can be used for direct photography of the sun (ND4, not NDx4!!!!).
(!!! only for the camera, our eyes need ND5 -Baader sunfilter- or more !!!)
With different cameras they are used for long sky shots.
Exposures of one minute or more let the moving people disappear in a crowded city.
...and we have the chance to shoot lightning at daylight.
These are the choices:
B&W filters and Neutral Density factors
| common name |
article | neutral density |
f stops | time factor |
transmission | diff. brands |
| NDx2 | B&W 101 | ND 0.3 | 1 | 2 | 50% | hoya,hama e.a. |
| polarizer | 1.8-2.5 | appr. 4 | appr. 25% | |||
| NDx4 | B&W 102 | ND 0.6 | 2 | 4 | 25% | hoya,hama e.a. |
| NDx8 | B&W 103 | ND 0.9 | 3 | 8 | 12.5% | hoya,hama e.a. |
| NDx4 + NDx8 | ND 1.5 | 5 | 32 | 3% | hoya,hama e.a. | |
| B&W 106 | ND 1.8 | appr. 6 | 100 | 1% | ||
| NDx4 + NDx4 + NDx8 | ND 2.1 | 7 | 128 | 0.8% | hoya,hama e.a. | |
| B&W 110 | ND 3.0 | 10 | 1000 | 0.1% | ||
| photo sun filter |
Baader | ND 3.8 | appr. 13 | 10 000 | 0.01% | |
| B&W 113 | ND 4.0 | 13 | 10 000 | 0.01% | ||
| astroSolar | Baader | ND 5.0 | 16.5 | 100 000 | 0.001% | |
| B&W 120 | ND 6.0 | appr. 20 | 1 000 000 | 0.0001% | ||
| variable 77mm ND2x-8x |
singh-ray | ND 0.3-0.9 | 1-3 | 2-8 | 50%-12.5% | |
| 2 polarizers | 4-?? | 16-?? | 6%-?? |
Baader filters are square folia that have to be fixed.
They are sold for telescopes.
Arithmetic:
If you combine these lenses, simply add the stops and multiply the factors mentioned above.
So NDx8 + NDx8 give you 6 stops, factor x64 and 1.56% transmission.
But most neutral gray filters are not coated, it is not a good idea to combine them.
Exposure
This is an example for the changes in exposure, starting with daylight: f/8.0 t:1/125
A B&W110 needs 8 seconds of exposure with the same aperture
Usage: look for the exposure time of the test picture in row: "0"
and find the new time under your used filter
Take a test shot and find the perfect exposure time.
These times are just a hint, your camera may need slightly different times.
Especially analogue cameras need a correction (Schwarzschild Effekt).
B&W Filters - Exposure
| NDx2 B&W101 | NDx4 B&W102 | NDx8 B&W103 | B&W106 | B&W110 | B&W113 | B&W120 | ||
| aperture/stops | 0 | 1 | 2 | 3 | 6 | 10 | 13 | 20 |
| 1,4 | 1/8000 | 1/4000 | 1/2000 | 1/250 | 1/16 | 1/2 | 32sec | |
| 1,8 | 1/8000 | 1/4000 | 1/2000 | 1/1000 | 1/128 | 1/8 | 1sec | 64sec |
| 2,0 | 1/4000 | 1/2000 | 1/1000 | 1/500 | 1/64 | 1/4 | 2sec | 2min |
| 2,8 | 1/2000 | 1/1000 | 1/500 | 1/250 | 1/32 | 1/2 | 4sec | 4min |
| 3,5 | 1/1000 | 1/500 | 1/250 | 1/128 | 1/16 | 1sec | 8sec | 8min |
| 4,0 | 1/500 | 1/250 | 1/128 | 1/64 | 1/8 | 2sec | 16sec | 16min |
| 5,6 | 1/250 | 1/128 | 1/64 | 1/32 | 1/4 | 4sec | 32sec | 32min |
| 8,0 | 1/128 | 1/64 | 1/32 | 1/16 | 1/2 | 8sec | 64sec | 1hour |
| 11,0 | 1/64 | 1/32 | 1/16 | 1/8 | 1sec | 16sec | 2min | 2hours |
| 16,0 | 1/32 | 1/16 | 1/8 | 1/4 | 2sec | 32sec | 4min | 4hours |
| 32,0 | 1/16 | 1/8 | 1/4 | 1/2 | 4sec | 64sec | 8min | 8hours |
| 64,0 | 1/8 | 1/4 | 1/2 | 1sec | 8sec | 2min | 16min | 16hours |
| 1/4 | 1/2 | 1sec | 2sec | 16sec | 4min | 32min | 32hours | |
| 1/2 | 1sec | 2sec | 4sec | 32sec | 8min | 1hour | 64hours | |
| 1sec | 2sec | 4sec | 8sec | 64sec | 16min | 2hours | ||
| 2sec | 4sec | 8sec | 16sec | 2min | 32min | 4hours | ||
| 4sec | 8sec | 16sec | 32sec | 4min | 1hour | 8hours | ||
| 8sec | 16sec | 32sec | 64sec | 8min | 2hours | 16hours |
You will notice that most of the long exposures show "warm" colours.
These extreme filters don't block the light below 660nm effectively.
The B+W-UV/IR-interference-blocking filter 486 in front (!) of the ND filter
removes this effect.
Crossing two polarizers should be a good trick too.
Two identical polarizing filters should give a perfect adjustable gray filter.
....I have tried my polarizers: they were not good enough!
..and this is the trick:
Circular type polarizers depolarize in a second step! Use a linear ploarizer first and a circ. polarizer as second filter!
Most of the long exposures are taken of wet surfaces.
The reflections add to the mystic effect. Polarizers can eliminate these reflections.
I needed a manual exposure, the camera did not like the dark environment.
Adjustments have to be taken without the filter, there is a dark screen otherwise!
So I take a test picture and calculate the necessary aperture and time.
Caution: SLRs need a cap on the view finder!
..and don't forget to look at this inspiring thread:
Reichert-ultra long exposures
Graduated gray filters
This page deals with normal and extreme gray filters.
There are also graduated gray filters that try to correct differences above and below the horizon.
We still need these filters because our little sensors have a small contrast range.
Using HDR correction with a set of bracketed shots is another approach to this problem.
This works only with non moving objects!
Just in case, that your horizons are not always in the middle of the pictures,
please look at the cokin system (A or P).
These modular filters can be adjusted
- and it is a fine system for all needs too.
wiki graduated filters
wiki cokin
Some links leading to further information:
Wikipedia neutral grey wiki
Variable polarizers?:NDx2-x8 variable singh-ray
Thanks for visiting my pages! Have a nice day - Sven
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All images are copyrighted by © 2005-2007 Seemolf last update 05.may.07 20:00