Infrared photography has long facinated photographers. To capture invisible light effectively has been the sole realm of the patient, the lucky, the experienced few. On film Infrared not only requires special handling of the stock, but also special in camera handling and shooting.
With the advent of digital cameras a new opportunity opened up for photographers. It was now possible to view Infrared results in the field rather than back in the darkroom. In many ways it took the guesswork out of the process and added back something closer to in the field experimentation.
Many reviewers of the Sony F707, including Shutterbug, have asked the question "Is the Sony F707 the ultimate Digital Infrared Camera"?. In many ways the answer is both yes and no. There are some aspects of the F707 that make it a very good IR camera and there are others that make it kind of clunky, and other cameras tend to handle those things better.
We will primarily focus these articles on the Sony F707 "NightShot" capability. The Sony DSC-F707 is one of the first Sony digital cameras to include the video camera capability of "NightShot:" in a still camera. NightShot enables the camera to become more Infrared Sensitive than normal. There are several benefits of this sensitivity to the Infrared Photography Enthusiast, and several disadvantages as well.
In this series of articles we will examine the F707's capabilties, explore the various ways to exploit the capabilities and characteristics of the camera, as well as examine as best we can the artifacts associated with the F707. In addition, if anyone from Sony is listening, we'll include a wishlist for the pro and prosumer.
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The F707 is one of the first 5megapixel cameras that has a specifc infrared mode (actually there are two, but only one is useful for Infrared Imaging - since the "NightFrame" mode switches to a full color mode for the image capture).
All digital cameras have a "filter" in front of the CCD that filters large amounts of UV and Infrared light. This is designed to cut down on "noise" from the Invisible spectrum since most CCD's are highly sensitive to the invisible spectrum as well. It is not uncommon for digital infrared enthusiasts to perform surgery on their cameras to remove this filter. Many Nikon CoolPix enthusiasts, being the most daring I have seen so far, have published numerous pages on the web of how they performed IRFilterectomies on their CoolPix cameras.
So when Sony released the F707 with it's "NightShot" mode, it gained quite a bit of attention. Unfortunately in my searching of the web, Nikon users seem to be far more enamoured and vocal about the IR sensitivity of the latest Coolpix 5000 and earlier models, than Sony users are of their F707 - there are already more than half a dozen Nikon IR galleries and I can't seem to find one for the F707 that deals with Infrared. Thus this series of articles.
There are two real advantages to the F707 over other cameras. The first is that by default NightShot mode removes the IR/UV filtering (there is a small mechanism that moves the filter out of the way of the CCD - I'm guessing a small solonoid). The second is that you are doing "realtime" Infrared.
The later point is very important as it fundimentally changes the way you can now take infrared photographs. Let me explain a little futher. Since CCD's are inherently IR sensitive, even with the blocking, it's possible to do time exposures with a Red 25 filter on most CCD cameras and achieve very good results. This is a technique commonly practiced by Nikon IR enthusiasts, and a technique many like myself have employed with other digital cameras, such as the Sony DSC-CD1000. Time exposures on the CD-1000 were taking on average 2 - 4 seconds for best results with basic Red 25 filtering. Obviously this takes the shot out of the realm of a handheld - it's a tripod shot only.
The advantage of the F707 in a stopped down NightShot mode, and is evident in every shot I took in these sections, were they were all shot handheld, realtime, and seen through the viewfinder shots. This opens up a whole world of different possibilities to the IR enthusiast.
One of the disadvantages of using NightShot is that by default Sony has chosen to turn on the two (pretty effective) Infrared Targetting Emitters, and it uses these to illuminate the subject at close range. The problem is, that if you use any filters, these emitters reflect off the inside of the filter, then reflect off the lens, then reflect off the filter and so on - you get the picture. So you end up with an image that has what looks like two tracks of light effecting both sides of the upper part of the image.
To solve this problem I went to Home Depot and picked up some rubber sheeting. From this sheeting I cut two round doughnut shaped pieces of rubber to use as inserts between the adaptor ring and the lens assembly. Essentially to cover the Infrared Targetting Emitters. Since my attempts at covering the emitters was pretty makeshift I would love to be able to use some other material. So if others experiment with this idea please let me know what kinds of things you came up with mailto:stuart@thelens.com.
Equipment Recomendations:
| Filters | |
| Red 25 | Hoya Produce a reasonable Red 25 Filter that is not expensive and has a lower profile than the Tiffen Red 25 - throughout the article when I refer to Red 25 I used two of these stacked. |
| 89a | Harrison and Harrison make an outstanding Red 98a filter - I would highly recommend adding this to your kit |
| Neutral Density 4x and 8x | The only exposure control you have is control over the amount of light you let into the lens you will need some neutral density filters - I would recommend carying one 4x ND and two 8x ND's - Additionally a warming polarizer seems to do well in the case where might want to add a small amount of stop. |
| Adaptor Ring | Since I wanted to keep the vignetting down to a minimum, I chose to use 77mm filters and a 58mm to 77mm step up ring |
| Something to cover the IR Emitters | See note above |
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As mentioned before there are several advanatages and disadvantages in using the Sony F707 for IR work. The first disadvantage is that you have no control what so ever over the exposure from the F707. The F707 when placed into "NightShot" mode displaces all manual, scene, and lens controls, other than focus. The F707's automatic exposure system is functional and the camera will do it's best to expose the image correctly as long as you manually control the light. The second thing is that Sony did not design the NightShot mode to really function in daylight so you need to compensate with filters that stop down the light to the lens (see previous section for filter recommendations). Additionally the Sony NightShot mode results in a "green" image. There is no grayscale mode within in the camera (which I thought was strange).
I took the F707 out into the local Landscape Arboretum (it was one of the few places I could find some greenery here in Minnesota in the winter - the milder than average winter has helped as well). The winter light is bright, and the reflections from the patches of snow that were still on the ground probably helped the scene illuminate more than normal, but I liked the results.
I experimented at two different times of day - the first day closer to noon with a bright sunny day. The second occasion was closer to sunset and this day I experimented with two different sets of filters (using the filter combinations described in the previous section).
The first time I took out the F707 I only had available two Red 25, and a Warm Polarizer. I found very quickly that that was not enough to stop down the camera enough, so dashed off to find a ND filter and ended up using two ND 4x (the only ones I could find in the area) as well as the red 25 filters. You now get the picture of why I went with 77mm filters instead of 58mm filters (the 58mm ganged that much would have very badly infringed on the frame edges).
The first observation was that one Red 25 filter really didn't seem to be enough - using two Red 25's seem to add more density to the image. The ND filters basically stop the whole thing down. I found in bright conditions the 8x ND will become your friend (so ordered two from B&H right away)!
One of the Artifacts of shooting NightShot is that the IR light spread in NightShot mode does not seem to be evenly distributed over the CCD - this becomes apparent in a vignetting effect that seems to effect the upper left and lower left of the image (I have seen this in other peoples examples with the F707 as well). I am not sure if this is a result of the lens, or the CCD, or the focal chamber itself. Whatever it is, the center seems to be inherently "hotter" than the rest of the exposure especially the edges.
There are a couple of things I've found that help to compensate for that. The first is counterintuitive, and that is to slightly overexpose the image. This seems to work better with the Red 25 combination and the 8x ND, than the 89a Harrison and Harrison, however the alternate use of a 4X ND filter with the H&H will enable you to control this "over exposure" better.
Here are two side by side examples. The first was show with the combination of two Red 25 and One ND 8x, and the second shows the H&H and ND 8x.
| 2 Red 25 and 8x ND | 1 89a H&H and 8x ND |
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As you can see the Harrison and Harrison produced an image with a higher density than the typical Red 25 Image. I believe that there are times when artistially you may want either effect - a more dense image or a lighter less dense image. Almost all of the images displayed in these sections are not modified - they were imported into photoshop and an "autolevels" was applied. In most cased the images display a green tinge - this is a color artifact from the NightShot, and after looking at it awile I kind of ended up liking it so did not convert the images to greyscale.
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If I were to favor a particular filter set for the day I would have to say that I was really impressed with the density of the Harrison and Harrison combination. However the image to the left was shot with the red 25 combination. The images below were shot with the H&H combination.
One of the real drawbacks of the NightShot mode is that you can not record any instrumentation on the image. You really don't have a record of Focal Length, F-Stop, and Shutter Speed. This makes the replication under similar conditions nearly impossible. The best you can do is externally meter and normalize that data later on for a common experience.
The facinating thing is that using the F707 for Infrared is like using a state of the art digital camera in a mode that goes back to the turn of the century.
| 89a H&H and 8x ND | 89a H&H and 8x ND |
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As you can see the best results were when the sun was at my back. These shots were taken about an hour before sunset and you can see the shadows gave an interesting perspective to the second image. Again, the Harrison and Harrison provided the best density.
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One of the things that makes the F707 very attractive is that it has an inbuilt mechanism to lift the IR/UV filter out of the way of the CCD. This is very cool, but as mentioned previously, this is only available in NightShot mode, and all other aspects of the F707 are disabled when NightShot is engaged.
So top of the wishlist - it sure would be nice to be able to control different aspects of the exposure (shutter, aperture) by being able to enable the "NightShot" and keep full camera control.
As a potential hack - I have been hunting the web for someone who has modified their F707 with a switch to flip the IR filter out of the way and leave the camera in regular exposure mode - if anyone out there has experimented with any modification of this kind, please let me know.
Next on the wishlist would be a way to shut off the Infrared Emitters manually - since NightShot mode doesn't really demand that they be used, and since they are really only useful at close range, having them default on is an inconvenience.
| 2 Red 25 and 4x ND and Warm Pol | 2 Red 25 and 4x ND and Warm Pol |
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The above images were taken from that first day utilizing 2 Red 25 filters, one 4x ND filter, and 1 Warm polarizer - some slight vignetting is visible since I hadn't discovered the slight overexposure trick yet. The image at the top was shot with 2 Red 25 filters, and 2 4x ND filters.