Digital Photography Technique > Taking Photos
A Guide To Infrared Photography
Rob aka [minolta mad]:
As promised i have written a guide as to how I take my Infrared Photographs.
Rob
Introduction
Infrared light is technically not a light source, it is invisible radiation, that our eyes cannot see but the sensors of our digital camera’s can.
By shooting in infrared, we can get some weird and wonderful effects, green foliage ends up looking like it has snow settled on them, due to the way it reflects IR wavelengths, blue skies and water end up very dark (near black) depending on which IR filter you use, as they absorb IR wavelengths.
If we shoot colour IR with custom white balance settings then truly weird colour combinations can be seen.
There are however some special problems that IR photography presents, focussing, exposure and some lenses do not allow the shooting of IR photography.
So what do we need to take IR photographs.
1. IR sensitive DSLR
2. IR suitable lens
3. IR filter
4. Tripod
5. Cable release (essential for shutter speeds in excess of 30-200 secs)
That’s really it.
In the tips below is what I have picked up and learnt from shooting Infra Red,
and what I believe to be correct.
If any information is inaccurate then I apologise and stand to be corrected.
Hopefully this information may answer a few of the myths around this type of photography and may encourage some other people to give it a go.
If anybody has any questions or queries then or myself or someone else will try to answer them.
Or indeed any tips themselves, then paste them in this thread so we can all benefit from them.
Rob aka [minolta mad]:
Testing camera for sensitivity
All camera manufacturers go to great lengths to block out as much IR light from reaching the sensor as possible, as this causes focusing,colour,metering and exposure problems.
The way they do this is to place a filter in front of the sensor called an Internal Infra Red Cut-off-filter (IIRC’s) often called Hot Mirrors.
Different manufacturers use different “hot mirrors” so some DSLR’s respond better to IR light than others.
To test whether or not your particular type of DSLR is suitable for IR photography the easiest way of doing this is the “TV REMOTE” Test.
Basically take a picture of your tv remote with your camera whilst pressing one of the buttons so a IR signal is transmitted from the remote.
Take the picture using an exposure of 5 secs at f/5.6. You should see a white light emmited from the sensor of the remote, the brighter the light the more sensitive the camera is to IR light. If no light is seen then your camera is probably not any good for taking IR photographs.
Image taken on A700, iso 200, f/5.6, 5 seconds
All you need to do now is buy yourself an IR filter.
From experience we as Minolta/Sony owners are lucky as our DSLR’s are suitable for taking IR photographs.
I have used the
5D
7D
A700
And successfully taken IR photographs with them, although I have not used the following camera's, I have been informed by other members that these are also suitable for IR.
A100
A300
Rob aka [minolta mad]:
Lenses
As with DSLR’s not all lenses are suitable for taking IR pictures.
Some produce what are referred to as “hot spots”, no one knows exactly what causes these hot spots but it is largely believed that it is the IR wavelengths effectively reflecting at different angles within the inside of the lens, and more “IR light” hitting the sensor in one “spot” rather than being evenly distributed.
A hotspot pic -
Its not always in the shape of a “spot” the hotspot, sometimes it causes a streak or streaks.
Streak pic -
Thanks to Springtide for this image.
There is no way of telling which particular lens will cause hot spots until it is tried and it either produces them or it doesn’t.
It is believed that wide angle lenses and especially zoom lenses are more likely to produce hotspots than fixed lenses due to their complicated optical systems.
Lenses that I have used or know that don’t cause hotspots
Minolta 35-70 f/4
Minolta 50 f/1.7
Sony CZ 16-80
Tokina 28-80 ATX-Pro
Sigma 28-70 EX DG 2.8
Lenses that I have used or know that do cause hotspots
Konica/Minolta 17-70 kit lens
Minolta 17-35 G
Minolta 28-70 G
Tamron 17-50 f/2.8
I know this list doesn’t have a lot of lenses on it at the moment, but it will be updated as myself and others find lenses that do or don’t work.
Rob aka [minolta mad]:
Infrared Filters
Like everything in photography there are several IR filters to choose from. These range in price from £25 up to £200. The more expensive one’s it is alleged tend to give more even results as they have stricter controls in place to ensure they are of the highest quality when they leave the manufacturers.
Different IR filters block some or all visible light and allow different amounts of IR light to pass through them, giving very different results.
Infra Red filters are measured by how much IR or near IR light they allow to pass through them, as there is no “standard” for how this is measured, it is difficult to really know what effects different filters will have until they are tried.
These filters are measured in ‘nm’ (nanometers) and the range used in photography is between 520 nm and 900 nm
I do not fully understand all of the transmission rates and effects these rates will have and how they will look when taking IR photographs.
So recommendations and seeing the effects different filters have by other people’s results are the way to go
The Hoya R72 filter will give the images taken a complete red colour until processed or converted to Black and White, as this allows some visible light in the far red spectrum to pass through the filter. Whereas the B+W 093 filter completely blocks all visible light and gives True IR pictures, but a sensitive IR camera will be needed to record the images or extreme exposures would need to be used.
IR filters manufactures.
Hoya See Here
B+W See Here
Cokin See Here
Lee See Here
Sign Ray See Here
Tiffen See here
Heliopan See Here
One possible problem with the square type slot in filters is that light can creep around the sides of the filter and ruin the shot ( I have heard of this but have not used this type of IR filter, so cannot comment)
By far the most popular IR filter is the Hoya R72, probably because it’s the cheapest filter and most easily available and gives good results.
For a reputable Ebay dealer in the UK See Here
I have used this dealer several times and the filters costs under half of what they cost in the shops.
Rob aka [minolta mad]:
Focussing
One of the major obstacles in IR photography can be focussing,
“But only if you let it be”
First of all you’ll need to use manual focus, and secondly, because of the wavelengths IR light are transmitted at, it causes a focus shift of 1/400 th of the focal length used.
And unless the focus is adjusted your images will be out of focus.
A lot of the older lenses have a red R, a red line or a red dot, this indicates the IR focal shift point.
To use this – focus on the subject that you wish to be your main focal point and make a note of what distance this is, eg 30 ft, Then place your IR filter on your lens and then align the distance your subject was at on the red dot/line/R
The image below is focused for 30 ft at 35mm, where as the lens is at 50mm, i will change this pic soon :-(
Then the focus will be spot on for the subject at that given distance.
For newer lenses that don’t have the IR mark on them then the only way to ensure your pictures are in focus is to use the Hyperfocal Distance.
The goal of hyperfocal distance focusing is to maximise the DOF (depth of field) and ensure that the maximum amount of the image is in focus. Effectively focusing
½ way into the image, so everything from 1/3 to infinity is in focus.
For a more detailed explanation See Here
Below is a Hyperfocal Distance chart for APS c sized sensors.
Chart in feet
Focal length
15 mm 17 mm 20 mm 24 mm 28 mm 35 mm 50 mm 100 mm
f 2.8 8.79 11.29 15.62 22.50 30.62 47.85 97.64 390.58
f 5.6 4.39 5.64 7.81 11.25 15.31 23.92 48.82 195.29
f 8 3.08 3.95 5.47 7.87 10.72 16.75 34.18 136.70
f 11 2.24 2.87 3.98 5.73 7.79 12.18 24.85 99.42
f 16 1.54 1.98 2.73 3.94 5.36 8.37 17.09 68.35
f 22 1.12 1.44 1.99 2.86 3.90 6.09 12.43 49.71
Chart in meters
Focal length
15 mm 17 mm 20 mm 24 mm 28 mm 35 mm 50 mm 100 mm
f 2.8 2.68 3.44 4.76 6.86 9.33 14.58 29.76 119.05
f 5.6 1.34 1.72 2.38 3.43 4.67 7.29 14.88 59.52
f 8 0.94 1.20 1.67 2.40 3.27 5.10 10.42 41.67
f 11 0.68 0.88 1.21 1.75 2.38 3.71 7.58 30.30
f 16 0.47 0.60 0.83 1.20 1.63 2.55 5.21 20.83
f 22 0.34 0.44 0.61 0.87 1.19 1.86 3.79 15.15
Another annoying thing with focusing in IR is that if you have to re-focus or re-frame your shot at any time the filter has to be removed and the shot re-framed/re-focused before replacing the filter onto lens.
So to sum up :-
1. Compose picture
2. Determine focus
3. Place filter onto lens
4. Re-focus (using red dot or hyperfocal distance)
5. Take photograph
Navigation
[0] Message Index
[#] Next page
Go to full version