Software Extravaganza Tutorial Infrared Photography Focus Stacking Infrared Photography Tutorial
without gutting the camera. (
Updated on July 9, 2009 )
Introduction What we want is a picture in which the light is not visible light but infrared radiation reflected by objects in the scene. In general the largest and only source of infrared radiation is the sun, opaque objects reflect a certain part of this infrared radiation and that is what we captured with the camera. As infrared radiation is on the outside of the visible light spectrum the results we get can be quite surprising.
any camera in general is quite sensitive to infrared radiation because they have a filter that filters in front of the sensor largely (but not all!) Infrared radiation that comes with it. Some photographers who specialize in infrared photos they do is remove this filter and so the camera is converted into an IR camera.
The counterpoint is that the camera no longer fit to take normal photos so in general this is not very desirable.
In a normal picture the amount of infrared radiation received by the camera in comparison with very little visible light so that the IR filter of the camera is usually not too strict, since it need not be, and this is essential to use IR filters and take infrared photos.
Without the option to turn the camera left is to use an infrared filter, the filter is screwed in our lens and filters the visible light letting infrared radiation. This infrared radiation is going to run into the sensor IR filter so will need a long exposure to achieve a correct exposure. The better or more strict is the IR filter of the camera exposure longer necessary. For this reason, some sites say that this or that is best for infrared camera but the reality is that the only thing that varies is the exposure time, any DSLR is for infrared photography provided when we have the filter, tripod and long enough .
Filters ... There are many infrared filters, the filters are identified by the frequency beyond which keep out the light.
700nm filter will filter all that is less than 700nm and let spend the rest.
What each filter passes we can understand about this little board:
- 700nm: Quite visible light (red) and 720nm
- Infrared (Hoya R72) Something visible and infrared light 760nm
- : Just something visible and infrared light 830nm
- : No visible light, infrared only 850 or masnm
- : Pure infrared filtering more and more and more
average exposure times on a sunny day with an XTI for filters up mentioned are:
- 700nm: 10 to 15 seconds
- 720nm: 20 to 25 seconds
- 760nm: 1 to 3 minutes
- 830nm: 2 to 6 minutes
900nm - : You can get 20 minutes (only makes sense in cases of forensic and other studies)
A pure infrared picture is totally black and white with 760nm filters or more photos will be strictly B & N. If you want pictures
color filter need to miss some visible light which will give us the color in the photo.
The big problem with the selection of filters If we understood so here we need a filter to let some light pass visible and infrared rest the problem is that depending on the camera and the filter model we need can vary. If the filter is very clear too pass up the photo visible light and be exposed to visible light most filtered red and IR only slightly. If the filter is too dark a picture we all white and black.
vegetation is the key blue, which is the result of filtering the green with a red filter, if what we get is blue means that the original was green and that is not IR, visible light is!
When the filter is too clear:
What we see is actually a photo taken with a dark red filter, ie visible light we are exposing filtered red. This produces effects that can be very beautiful but not doing infrared photography. Personally I believe we can take lots of photos interesting with this type of filters.
When the filter is too dark:
What we see is pure infrared radiation captured by the sensor, nothing in this photo or a drop of visible light, so the picture is completely black and white. The exposure time is here very little, usually more than 2 minutes and it generates much noise and movement of anything that moves with the wind. If the B & N we like and we can deal with noise and movement to this type of filter is a good solution.
When the filter is right:
What we see here is a mixture of visible and infrared radiation. The vegetation is white because that is the color when making the vegetation reflects infrared light, although most of the exhibition is based on reflected infrared light filter has missed "something" of visible light that provides the color in photo .
lenses and IR photography
Unfortunately not all lenses are suitable for infrared photography. With certain lenses refraction between the internal elements of the same produce the effect known as "hot spot" which is basically a very nasty stain in the center of the picture, as if that area had been exposed much more than the rest of the photo.
This problem can be corrected in PP but I do it is extremely annoying. The following link
can find a list of lenses that do not occur and that if they produce hotspots.
http://www.lensplay.com/lenses/lens_infra_red_IR.html
Among the most popular lenses the 28-135 and 50mm 1.8 mkII going very well in IR.
Exposure
generally putting the filter through the viewfinder does not see anything, with a day of sunshine and light of 700nm filter we get to see the scene between shades of red in the viewfinder but it would be an exceptional case.
IR professionals use a viewfinder accessory shoe mounted flash, sometimes get on ebay and used to compose the filter position. Mortals up without the filter and then screw the filter again.
Keep in mind that the focus on IR is a bit outdated with visible light bulb so it should take at F8 or F11 and focusing a little bit ahead of where we want the real focus, taking into account the opening girl and that the gap is little that brings very good general results. At f4 and below may need some pictures of trial and error to guess where do the normal focus to focus IR fit.
If we think a final photo in B & N it is best to expose for the green channel, for that we use the camera's histogram in RGB mode, we start with an exposure to a rule of thumb according to the filter you use and then adjust the exposure time for adequate exposure of the green channel. The red channel will blow and blue can be noisy. Then on the PP simply "delete" green and red channels and we have a picture B & N very acceptable.
For pseudo-color photos on the question is more difficult because if we take care not to over-expose the red channel we sub-state green and blue channels of the photo. "Right" is technically take 2 photos (or three) one for the red channel and one for green and blue and then combine these channels in the PP in a single photo. Those who by now have lost all the hair may simply seek a compromise in which green and blue channels have
some detail and red is not burned completely. Keep in mind that in general the red channel is the one who recorded mostly visible light and green and blue channels infrared radiation.
Be careful with the ISO as being blue and green channels underexposed in general there is plenty of noise in high ISOs this is magnified if you take just one picture is recommended to use the lowest ISO the camera. Whether to combine multiple exposures can be drawn in ISO400 or if the camera allows it to 800 without much trouble. Show
with Hoya R72 filter The Hoya R72 is one of the most popular IR filter DSLRs without some important tips the results can be somewhat random.
Something fundamental to consider is that if we took the photo in RAW without setting a custom WB histogram we see in the camera will not be the real histogram jpg but the histogram generated with the incorrect settings of WB. Setear a custom WB is somewhat cumbersome so it is advisable to learn to portray the filter without touching the WB. The key is relatively simple: Over-exposed!.
If we take care not to over-expose the red channel we will end with a photo with 95% 5% visible light and IR light because the red channel capture mostly visible light. For a correct IR effect should be relatively well exposed green and blue channels with the WB to "auto." As a first effect we see that the red channel is absolutely burned disappearing even from Histogram. Do not despair because the histogram shows that the camera is not RAW but JPG WB has a wrong, when you set the WB in the RAW development will magically re-appear the red channel that provides some light visible to the photo.
times of exposure to full sunlight tend to be in 20 or 30 seconds with this filter.
Post-Processing
The post-processing of IR photography can be as simple or complex as you want.
The first step is to adjust the white balance, in general it is to select any area of \u200b\u200bthe photo that has targeted vegetation and adjust the corresponding goterito, as assumed that the vegetation in Infrared blank this usually works well well. Temperatures range around 2000K. For those who do not take in RAW
or may not have to adjust the WB in the chamber using a custom-shaped photo of some vegetation and white card. Drawing on RAW the white balance setting on the camera is not necessary, are just metadata.
Once set the white balance there are 2 decisions to make the first is if we leave the photo in pseudo-color or pass it to B & N. The second decision is about reversing the red and blue channels of the photo, many do, some do not and the truth of the Milanese is that it depends on how we like but the end result, but try not cost anything.
After all this is to adjust levels and / or curves because in the infrared world things are not like in the world of visible light and can achieve results by moving the curves particularly interesting. Finally
usually required noise reduction and sharpening selective areas want more sharp.
Conclusions: For
those seeking B & N filter can start with a good economic via ebay, you have to pay about 20 dollars and usually come without problems. Those seeking a bit of color will have to fall in the almighty Hoya R72 filter is somewhat more expensive. Remove RAW is essential as well as some experience in RAW and adjust reveal the white balance. The tripod is absolutely essential.
My humble set of experiments can be Infrared (
here )
