photo:filters
photographic filters
Introduction:
although one can achieve many effects in image editing programs such as Photoshop that simulate the effect of many of these filters, it is usually better to get the image right in the camera without need for image manipulation in the computer which tends to degrade the image in other ways.
some effects cannot be easily reproduced in Photoshop such as polarising or infra-red
even more important is the problem that digital cameras have limited dynamic range and it is very easy to burn out highlights and irreversibly lose detail in them. Thus graduated optical filters become even more important in digital photography if one wishes to retain cloud details in a scene, or perhaps the brightly lit end of a room or corridor. There is still the problem though of objects that pass from dark to light areas potentially revealing the position of the graduated filter cutoff line.
One thing that no amount of Photoshop can fix is shooting into the sun, if you have the sun on the horizon and shoot straight into it you will end up with flare and a general washout of colour, use a ND Grad to block that light and the tonal range is captured again.
adequate lens hoods are imperative to reduce lens flare, particularly when shooting into the light source.
prices are approximate from
Vanbar 2005 to give you an idea of comparisons.
what would I use for digital photography?
UV filter to protect lens - consider removing it to take critical photos esp. those into a light source when flare needs to be controlled. Not much point spending $A70 on a filter to protect a $A200 lens though, and no point taking photos through a $A20 filter when using a $A1000 lens. So if you are going to remove the filter to take your photos, you can buy a cheap one, otherwise buy a multicoated expensive one.
circular polariser filter to darken blue skies, give more saturated foliage colours and reduce reflections on water or glass
ND400 circular ND filter to allow longer exposures such as needed to produce flowing water motion on sunny days
perhaps a ND8 filter to allow fill in flash on sunny days and still get wide apertures for shallow
depth of field (DOF)
ND graduated filters of the square design (eg. Cokin, Lee) to prevent the sky getting blown out. Don't bother with circular ones as you can't adjust them up and down for horizons, etc.
maybe an R72 infrared filter if you want to try infrared digital photography.
Filter systems:
screw-on filters:
slide in filters:
these are usually square glass or resin filters which slide into a holder which has been screwed onto your lens filter thread.
this enables the vertical or horizontal position of the filter to be adjusted to suit which is critical when using graduated filters that are used to darken the sky, etc.
these systems usually incorporate lens hoods that attach to the adapters
Cokin have 4 filter systems:
“A series”:
67mm filters for lenses with filter threads up to 62mm and focal lengths >= 35mm;
cost $A20ea for basic, to $A30 for graduated & up to $A50-60 for some special effects
“P series”:
84mm wide for lenses with filter threads up to 82mm and focal lengths >= 28mm;
filters cost $A25ea for basic, to $A35 for graduated & up to $A50-60 for some special effects
adapter available for A-P $A12
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“Z Pro”:
“XPro”:
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Galen Rowell 120x84mm graduated soft-step & hard-step ND filters (fit Cokin P)
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Gold'n'Blue Polarizer $US179 - changes the colour in polarised light only, thus quite natural
colour intensifiers
other systems:
Lee filters:
Lee glass filters 84mm to fit Cokin P
“Foundation kit” filter holder $A143 & lens adapter ring $A47
bellows lens hoods: $A220-440
100mm resin /105mm glass- $A130 basic; $A400 linear polariser; $A700 circular polariser;
150mm - $A176 grad;
100mm polyester: $A44 colour compensation;
150mm polyester: $A85 colour compensation;
Sinar
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Haida
M7 75mm system for lenses up to 67mm
“drop-in” filter slot closest to the lens to allow rotation of their drop in circular polariser filter
M10 100mm system for lenses up to 82mm
M15 150mm system
lighting filters:
Filters for colour photography:
Filters for B&W photography:
Filter factors:
filters often require an increase in exposure to allow for the reduction in light, and this exposure increase required is often expressed as a “filter factor” such that a filter factor of 2x means exposure must be doubled, ie. increased by 1 stop, and filter factor of 4x means 2 stops increase needed, while 8x requires 3 stops.
Filter factor | 1.25x | 1.4x | 1.6x | 2x | 2.5x | 2.8x | 3.2x | 4x | 5x | 8x | 16x |
f stop | 1/3rds | 1/2 | 2/3rds | 1 | 1 & 1/3rd | 1 & 1/2 | 1 & 2/3 | 2 | 2 & 1/3 | 3 | 4 |
polarising filters usually have a filter factor of 2.5, and thus require 1 & 1/3rd stops increase.
filter factors for color filters in B&W depend on which light source is used, whether daylight or tungsten, as bluish filters will have a much greater filter factor for tungsten light (eg. in this case, double that for daylight film), while the reverse is true for red filters.
neutral density filters are often given a different system:
0.30 = 50% reduction in light = 2.0 filter factor = 1 stop
0.60 = 75% reduction in light = 4.0 filter factor = 2 stops
0.90 = 87% reduction in light = 7.7 filter factor = ~3 stops
1.00 = 90% reduction = 10.0 filter factor = 3 & 1/3rd stops
2.00 = 99% reduction = 100 filter factor = 6 & 2/3rd stops
Removing stuck filters:
photo/filters.txt · Last modified: 2020/01/17 08:54 by gary1