‘Deep’ Infrared photography using a 850 nm filter over the lens of a 720 nm converted camera

I have repeated the trials I did with an 850 nm filter on my 590 nm-converted Nikon D80 with my new-to-me 720 nm-converted D90. I needed to increase the exposure by two stops compared with the value metered by the camera without the filter in place; as before I had to do this on manual because metering through the filter produced nonsensical results.

‘Deep’ Infrared photography using a 850 nm filter over the lens of a 590 nm converted camera

For black-and-white infrared photography I wanted to get darker blue skies and whiter foliage than I could using my converted Nikons with 590 and 720 nm filters over the sensor. So I bought a cheap 850 nm filter to fit over the lens. The grand total of £19.99 paid to an eBay seller soon had a made-in-China Zomei 77mm 850 nm filter arriving by post.

The only disadvantage of this route to ‘deep’ infrared photographs (actually ‘near’ infrared to physicists) is the opacity of the filter. You have to work with a tripod, frame the shot and then screw the filter onto the lens before pressing the shutter. Since I will use it for non-moving subjects the addition of the filter is only a slight inconvenience.

First of all I checked what exposure I would need compared with the exposure metered by the camera without the filter. I soon found that with the filter in place my 590 nm-converted camera on aperture priority over-exposed by about 6 stops, as you would expect since the meter is working somewhere in the visible light range. Kolarivision suggest a light loss of about 1 stop with their 850 nm filter. Sure enough, when I made a series of test shots at 1/3rd stop intervals in sunlight, 1 stop over the metered exposure was the best. However, 1 stop is the starting point for adjustment up or down depending on the amount of infrared radiation relative to the amount of visible light coming from the scene.

I keep my 590 nm-converted camera at minus 2/3rd stop (-0.7) exposure compensation (slightly less than suggested by Kolarivision for their 590 nm conversions). For convenience when using the  850 nm filter I now turn compensation to 0, take the metered reading on aperture priority, switch to manual exposure and add 1 stop. I also focus manually before adding the filter.

The two photographs, from my usual test site of out of the bedroom window, below show black-and-white conversions in Lightroom from my 590 nm converted Nikon without and with the 850 filter.

Infrared Processing in Lightroom

If you have your RAW image from an infrared converted camera in Lightroom, having to go to Photoshop or Photoshop Elements with Elements+ to swap the red and blue channels is a pain. When I made the move from Aperture to Lightroom 6, I was delighted to find, in a Google search, Jarno Heikkinen’s solution to the problem on his Capture Monkey website. His download provides Camera Calibration Profiles with reversed colour matrices for a number of cameras. To reiterate, it simply extends the profiles available within Lightroom. It does not, of course, work for jpegs.

I also remembered that Jason O'Dell had described an approach similar to, but easier than, changing Hue in Nikon Capture 2 using Viveza 2 (I have Nik Software as a plug-in for Lightroom).

I thought I would compare the basic conversions using these three methods. The starting point was a NEF image from a converted Nikon D80 with a 590 nm filter over the sensor.

As you can see there are differences from the same raw image. All I have done is to apply the conversion and then in Lightroom use Auto Tone. I have not done any further processing.

A Lightroom 6 to Photoshop Elements with Elements+. Red/Blue Channel Swap. Auto Tone in Lightroom

B Lightroom 6. Camera Calibration Profile Red/Blue Swap (Jamo Heikkinen). Auto Tone in Lightroom

C Lightroom 6. Edit in Viveza 2. Near 180 degree shift in Hue. Auto Tone in Lightroom

I then did a simple black-and-white conversion within Lightroom and these are the results:

Which method you prefer depends on the final look you are trying to achieve and how easy it is to get where you want to be. Each provides the starting point for further processing both in colour and black-and-white. For most purposes, particularly black-and-white, and at the moment I think I can manage with the wholly within Lightroom solution of Jarno Heikkinen, although for some faux colour images I rather like the Viveza 2 process. Whether or not I can manage completely without the channel swapping step in Photoshop time will tell as I try images with the different cut-off filters over the sensors of my converted cameras, with different white balance settings, with additional external filters and with different lighting.

How to—and how NOT to—get started in Digital infrared Photography

First rule: do not start with magazine articles such as those that have appeared in Amateur Photographer. Even a reader of the natural home of the head-in-sand luddite wrote to complain how misleading one article had been.

Second rule: Use the information available on the internet. It is far better than anything I have seen in a magazine both on taking and processing infrared images.

Third rule: Do not simply buy an IR filter and try it on an unconverted camera. The sensors of many cameras have virtually no sensitivity to the infrared end of the spectrum.

Fourth rule: To get started buy an infra-red converted Nikon D80 or D70 for £120-200 from the many available on eBay UK. You will pay much much less than the price of a conversion. This route has been completely ignored by the magazines. Could it to protect their advertisers? Also check which Nikon lenses are suitable for infrared since some show ‘hotspots’ on the image. Canon bodies—if you are that persuasion—are also available but less commonly than the old Nikons. Again check on websites which lenses are not suitable. The advantage of the old DSLRs over many converted compact cameras (also freely available on eBay) is that they offer RAW rather than just JPEG output, thereby offering greater opportunities for processing.

Fifth rule: If you do not want to pay for the full version of Photoshop to do channel swapping, use Photoshop Elements and buy Elements+ for US$12 which unlocks that capability.

These are some of the websites I found to be particularly useful in getting me started:

Lifepixel  and Kolarivision (good advice and guidance on their own conversions, filters and processing). Also this tutorial guide.

There are many other websites but some which were useful in the past are now out-of-date.

'Bridge' Cameras for Wildlife. A Retailer Gets the Message

The 'photographic' magazines may ignore 'bridge' cameras and only mention them in passing as new models appear but those of us who travel thousands of miles to see wildlife and natural habitats know what most travellers will be carrying: a superzoom bridge camera.

I see some in the photographic trade have now realised that the are not just selling to 'photographers' (the term is hard to define but I tend to think of amateur photographers as people who take photographs that are acceptable as photographs by other amateur photographers) but to naturalists who take still photographs and, sometimes, video. This advertisement from WEX arrived in an e-mail:

However, I am not sure they quite have the message. A 10.7x optical zoom is usually nowhere near enough.

The Nikon Coolpix P610 and Filters. What size and if at all?

Search as I might I could not find the filter size for the Nikon P610 in the manual. So I looked online and uncovered a whole can of worms. Somebody had enquired of Nikon the same question but had been told the P610 would not take filters, that the grooves inside the lens mount were not threaded and that any filter would only be lodged there and would fall out. Then somebody else stated that their 52 mm filter fitted fine.

Having a 52 mm filter in my hand (see previous post) I tried it on the P610. It fits perfectly. Firm as a rock. No problem at all. Here I am trying and failing to dislodge the filter other than by unscrewing it:

Problem solved but what were Nikon thinking of when they produced the camera and the manual?

An Extremely Cheap Variable Neutral Density Filter. How Does it Perform?

As I noted in my previous post, my new camcorder does not have a built-in neutral density filter. On the rare occasions I might use one under manual control in order to achieve an out-of-focus foreground or background, I invested in the cheapest I could find, just to see if it would be good enough for those few occasions.

I soon found some cheap variable density filters on eBay. I paid £7.79 including postage and it arrived a couple of days later.

Here is the picture from the eBay listing.

The Neewer filter seems well built but I will not tempt disaster by getting it wet.

There are graduations along the side with 'min' at one end and 'max' at the other.

I have read poor reviews of even expensive variable density filters. The problems seems to be inherent in having two sheets of polariser stacked one on top of the other. The graduations are non-linear, in other words, rotating the filter from A to B, say, does not increase the density by as much as between B and C They are not, like any polariser, suitable for wide-angle lenses and there are numerous reports of colour casts.

So, I decided to test the density at each of the marks on the scale. To do so I used the Light Meter app in my iPhone 6. I mounted the iPhone on a tripod, aimed at an evenly lit wall and measured the shutter speed at a fixed aperture. Therefore I obtained the difference in Exposure Value (EV) (i.e. stops) between having having no filter there and the filter at all its marks on the scale except 'max'. At 'max' the filter was unusable because of the appearance of a dark mesh.

Here are the results. The effect of the filter at its minimum setting was one and a third stop compared with the absence of the filter. Sure enough, there was a non-linear increase at each mark, with a steep increase in density towards the maximum end. The verdict was that with this information, density can be dialled in for a stop changes (to the nearest whole stop) from 1 to 6.

I also looked at the effect of the filter, using the same set-up, on colour temperature (Light Meter app gives a read out in degrees Kelvin). There was a shift which varied with setting:

How serious is the maximum shift in colour temperature? Well I took a (Raw) photograph on my Nikon D700 and adjusted its colour temperature to the 5476 K (the without filter red line in the graph above). I then made a copy and adjusted its colour temperature to the minimum value the filter produced (i.e. 5150). The result is below. Remember that these photographs were not taken using the filter, they are a simulation of the maximum shift in colour temperature that the ND filter produces:

Simulating the effect of the ND filter on white balance
Left WB adjusted to 5150 K; Right to 5476 K

No I could not see much difference either and any shift could soon be put right in Final Cut Pro X.

Finally, to look for any deleterious colour casts, I put the filter on the Sony AX33 camcorder and tried it at the various marks. I left the camcorder on automatic so that it would compensate for exposure and white balance. Could I then see any colour cast from using the filter? The short answer was no.

Therefore, I am really rather pleased with my £7.79 variable neutral density filter. What is more I find it fits my Nikon P610 superzoom bridge camera, but more on that later.