Dynax Digital Forums

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.

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.

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

What Makes A Good IR Image


In a way, any image can make a good IR image. But there are restrictions with the length of shutter speeds that are involved.

There are some people that specialise in IR wedding photography with converted digital slrs that allow normal shutter speeds to be used when shooting IR.

But generally because of the effects that grass, trees and plants produce images with these in make for good IR images as do ones with water and lots of sky.

But try anything, as recently I took an IR image on our coastline with seaweed on the rocks in the foreground, not expecting anything of note to come of it, I was pleasantly surprised with the result I got.

A700, iso 200, f/8, R72 filter, 55 sec exp

Processing in Black and White


You have now taken your first IR pictures, so how do you process them ?

Well, in a way the same as any other picture !

Once you’ve opened up your image in Elements or then convert to Black and White using either of Stefs many tips See Here

 
My way of editing are as follows.

Open up image in RAW, you’ll notice that the image is very red and will almost certainly contain some blown out highlights



Next would be to remove all blown highlights using the temperature and tint sliders first, then if there are still blown highlights remaining use the exposure and recovery sliders. 



Next would be to use a convert to black and white layer, I would move the sliders until the desired effect is achieved. Usually its only the red and yellow sliders that will have any effect.



Next would be a levels layer. With levels I usually move the sliders indicated to the start of the histogram where the detail rises. This may be done to one or both sliders it depends on what effect each one has.



Next I have added a contrast layer and added + 8 contrast. I have also used the dodge and burn tool on parts of the waterfall to make the water stand out a bit more.




I have not used a method I favour a lot when editing this image as it didn’t require it, but it is one that Stef came across almost straight away when editing in B/W.
And that is,  because the image is largely red only the red and yellow sliders have much effect in the convert to black and white mode, so when you try darkening the sky in the image the whites also end up becoming too dark.
Likewise when you try lightening the whites the sky becomes too light.
The way to overcome this is to make a selection of the part of the image you wish to darken or lighten using the lasso tool, when you have made the selection use the refine edge or feather tool so that the changes blend in and don’t stand out too much.
A figure of 30-40 pixels is usually about right.
Then using either a levels or convert to black and white layer, adjust only the particular part of the image that you want to adjust, like making the sky darker or making the whites of the tree’s whiter.

Links


Here is a list of links to websites and resources that I have found very useful in helping me understand IR photography and how to improve.


http://photonotes.org/articles/ir-myths/

http://www.pbase.com/dlarson2/ir_work_flow

http://heim.ifi.uio.no/~gisle/photo/ir.html#lenses


Too see more of my IR images, please check out the Infrared gallery on my website www.rnkendall.com