Nikon D7100 Infrared Conversion

I have a very unique Nikon D7100 – it is likely the first unit converted for infrared use – in the world. My D7100 is also likely the first to undergo two infrared conversions (more on this in a bit). I was fortunate to receive my D7100 from B&H as part of the first wave of product shipments. Apart from a night of putting the DSLR through its paces to ensure that there were no focusing problems or other issues, I didn’t have the D7100 for very long. For the many reasons Nasim outlined in his detailed D7100 review, and being very familiar with its predecessor, the D7000, I liked what I saw of this DSLR’s capabilities.

As some of you know, I have a passion for infrared photography and thought that the D7100 might be the ultimate infrared camera (for those of us in the Nikon camp!) and perfect for my needs. So despite having my D7100 for less than a day, I packed it and sent it off to one of the well-known infrared conversion companies. The customer service representative from the infrared conversion company confirmed that it was indeed the first D7100 they had seen. I will get to my thoughts regarding the D7100’s suitability for infrared photography (abbreviated as “IR” for the rest of this article), but first we have to follow its journey through the conversion process…

1) A New Infrared Filter Choice – The 665nm

My previous Nikon IR DSLRs, a D40X and D90, sported 720nm IR filters. The 720nm filters have been described as the most versatile of the various IR filters available, since they enable the camera to capture a significant portion of the IR spectrum. They also allow just enough visible light to reach the sensor and produce some interesting false color effects when using Photoshop’s Channel Manager control. Below is a photo from my D90 and a 720nm IR filter.

I had been looking over some stunning false color photos taken with IR filters, such as the 590nm and 665nm filters, that allowed more visible light to reach the sensor. You can think of my musings as, “The IR filter is always more colorful on the other guy’s camera.” After going through some tutorials on one of the conversion company’s website, and speaking with the customer support representative, I was under the impression that the 665nm filter might be the best of all worlds – rich IR capabilities combined with a wider array of false color processing capabilities.

I did read of some concerns regarding that the 665nm filter might render vegetation in subtler tones than the 720nm filter, but according to the IR conversion company tutorials, however, it seemed that this could be overcome easily enough using Photoshop’s Lightness slider to lighten the yellows (produced by using the Channel Manager’s ability to swap the Red and Blue channels). In speaking with the IR conversion company representative, he also confirmed that with a bit of Photoshop tweaks, I could achieve similar results as those of the 720nm filter. My mind was made up – I was going to order the 665nm filter.

As usual, I sent my main IR lens, a Nikon 16-85mm lens (consistently rated as one of the best IR lenses for Nikon DSLRs), along with the D7100 to enable the company to calibrate the pair. Since IR wave lengths are longer than those of visible light, IR conversion companies sometimes request that you send in your most-used IR lens along with the DSLR, so they can adjust the camera’s focus to that of the lens. Others modify the focus for an “average” IR adjustment value, but not to that of a specific lens. The adjustments made by the IR conversion companies can extend beyond what you are able to achieve with the AF Fine Tuning capability in most DSLRs. As with visible light, you should always test your lens via a tool such as LensAlign to ensure that you correctly calibrate your lenses to achieve optimum performance.

2) 665nm Filter – Second Thoughts

Spring had not yet arrived in Pittsburgh due to the unusual cold spell the area endured during the last few weeks of March. So as soon as I received my D7100, I immediately headed over to Pittsburgh’s Phipps Conservatory, a botanical garden with plenty of luscious green plants, perfect for testing an IR camera. I took along my D90 (with 720nm IR filter) to get some sense for how the two DSLRs stacked up against one another.

I spent a few hours walking through Phipps Conservatory putting the D7100/665nm combination through its paces. I shot quite a few photos using the custom white balance as well as Auto White Balance. I then headed off to Las Vegas for a business trip and brought the converted D7100 for a bit more testing.

I now had quite a slew of IR photos taken in a variety of lighting conditions (mostly sunny) that I could process. Since the 665nm IR filter allows a higher percentage of visible light to strike the sensor than the 720nm allows, it requires a different post processing routine. I was able to capture some very good (at least to my eye) images with the D7100/665nm combination. At the same time, I noticed that my shots were not quite as “crisp” as those taken with my D90/720nm – this related to sharpness as well as the brightness and contrast of the vegetation, one of best subjects for IR.

I spent the better part of 10-12 hours over the next week experimenting with different post processing techniques to develop the photos taken with the D7100/665nm. It didn’t take me long to have second thoughts regarding the suitability of the 665nm sensor for the D7100. I came to the following conclusions regarding the 665nm filter paired with the D7100:

2.1) Duller Vegetation With Less Contrast

Despite the claims of being able to whiten the vegetation to achieve similar results to those of the 720nm filter using the sliders found in Photoshop’s Hue/Saturation control, I found this nearly impossible in many circumstances. Under certain conditions, I could get close, but the 665nm sensor invariably produced vegetation that looked a bit gray and flat when compared to that taken with the 720nm filter. I could lighten the yellows a bit, but then found myself blowing out the details in some of the channels. This made for some interesting color IR shots, but if you appreciate the crisp whites and sharp contrast associated with the 720nm or higher IR filters, the 665nm may not be the best choice. Some of the 665nm’s duller vegetation could be improved by converting the image to black and white, but this negates some of the very reasons why you would select the 665nm filter.

The photo below is a good example of the “muddied” colors the 665nm filter sometimes produced.

2.2) Sharpness

Since the 665nm filter allows more visible light to reach the sensor, selecting a single focal point for sources of light with very different wavelengths gets a bit tricky. The same concern exists for colors that make up the visible spectrum, since each also has its own wavelength corresponding to a value on the electromagnetic radiation scale (EMR). Most lenses do a pretty good job of making sure that all of the colors of the visible light spectrum get to the same point on the sensor. But if you have ever seen Chromatic Aberration effects (colored halos on the edges of the surfaces of subjects in your photos), however, you have seen what can happen when the various colors of the visible light spectrum don’t focus at the same point on the camera’s sensor. Adding infrared light to the mix only complicates the focusing issues. Even with AF Fine Tuning tweaks, I was not able to get the same sharpness (all things being equal) with my D7100/665nm combination as I was with the D90/720nm pairing. The 720nm IR filter allows a smaller percentage of visible light to strike the sensor and thus doesn’t have the same degree of focus tuning challenges associated with the 665nm or 590nm filters. Was this a “killer issue?” No, but it was noticeable. Of course, after staring at my computer monitor for too long, I began to question my own judgment regarding the results. I asked my wife to look over some photos taken with the 720nm and 665nm IR filters. To my surprise, she was able to accurately identify photos taken with each, based on both their sharpness and their contrast, even after I was able to employ a similar false color processing scheme to them. She also liked the photos taken with the 720nm filter better than those taken with the 665nm filter.

2.3) Inconsistent Results

With my 720nmIR filter-based DSLRs, I could usually count on the same post processing settings to work for every photo taken within a given set (same time of day, same mix of cloud/sunshine, same lens, etc.). I might have to make some minor adjustments from photo to photo, but I got very consistent results once I fine-tuned a setting for a given batch of photos. I noticed that with the D7100/665nm combination, this wasn’t always true. From the same angle, using the same lens with the same settings, I could get some very different results simply by panning around slightly within the same scene. And while some IR conversion process firms do warn you about more variability with the 665nm and 590nm filters, I was surprised at how much I had to play with post processing settings for images that were taken a second or two apart and simply highlighted a slightly different aspect of the landscape. The increased variability of the D7100/665nm pair was likely due to the fact that, as I changed the angle of the lens or focused on different aspects of the landscape, the mix of IR and visible light varied more than what would have been captured with a 720nm IR filter. Again, this is not a deal-breaker, but the 665nm IR filter’s added variability did cause me to spend much more time processing my IR images than was necessary with my 720nm IR filter-equipped DSLRs.

Under certain circumstances, I was able to produce some very interesting false color IR images with the 665nm filter. On a different camera, the 665nm might have produced even better results. Here are a few that I believe came out fairly well with some Photoshop tweaks:

The duller vegetation, reduced sharpness, increased variability between shots, and corresponding increase in post processing time, however, were enough to make me want to switch back to the 720nm filter. This is not to indicate that there is anything inherently wrong with the 665nm filter or the conversion company that installed it. Some of my opinions are tainted by my own personal tastes. I do know others that have sworn by their 665nm filters and produced some excellent results using them on different cameras. But the process of using Photoshop’s Hue/Saturation control to have the 665nm filter mimic the results of the 720nm filter, touted by some conversion companies, isn’t the “magic sauce” they might have you believe – at least not when used on photos taken with the combination of the 665nm IR filter and the D7100.

3) Kolari Vision – The 720nm “Re-Conversion”

I knew that the D7100 was an excellent DSLR based on Nasim’s and others’ reviews, as well as my own assessment of its feature set. I also knew that I would get quite a bit of use out of my IR-converted D7100 over the next few years. The issue was not the camera, but rather how this specific 665nm filter, made by this manufacturer, behaved with the D7100’s sensor. IR filters are made by a variety of companies, including CDGM, Shott, Hoya, and Kodak/Wratten. And while some filters may have the same IR rating, often measured in nanometers (such as 590nm, 665nm,720nm, and 850nm), the truth is that each filter will vary in terms of its specifications from company to company and produce slightly different results. Add the variability of how different camera sensors deal with IR light and you can easily find that camera A, combined with 720nm filter from company B, produces very different results than camera C, combined with a 720nm filter from company D.

Below are some examples (reprinted from Kolari Vision’s website with permission) of how the same 590 IR filter behaves with different camera/sensor combinations (Nikon D90, Panasonic FH20, and Canon G10). As you can see, the results can vary quite a bit. Other IR filters may not show as much variance as you see in these photos, but you will get different results with various makes/models of cameras using the same IR filter.

Combining a healthy mix of both IR and visible light can play havoc with some sensors and lead to some compromises in the camera’s ability to correctly focus both types of light and/or deliver consistent results. The 590nm and 665nm filters simply are not an option for some point and shoot cameras due to the widely fluctuating results. This shouldn’t be too surprising, since the sensors available in most digital cameras are not specifically designed for IR light. The only way to know for certain what you can expect from a given conversion process is to find someone with the same make/model camera and a specific make/model of IR filter, and look over some of their photos. The good news is that you can easily find such a person(s) on one of the many photography forums. And most of the IR conversion companies have some good examples of popular camera models and IR filter choices.

So now that I had decided that the 720nm filter was a better fit for my D7100, I decided to bite the bullet and get rid of the 665nm filter. I wasn’t excited about having to spend the money for another conversion, but since I anticipated using this DSLR for quite some time and expanding my infrared photography efforts, I thought it well worth the cost to ensure that I had a filter that met my needs. I decided to investigate some of the other IR conversion companies. I came across Kolari Vision, a family-run business based in NJ. I was very impressed with their website, which I believe has some of the best guidance for those interested in IR camera conversions. I reached out to Ilija, one of the Kolari Vision’s owners. He was extremely responsive and quite interested in understanding the issues I had with the 665nm filter. Ilija was not too surprised to hear of my concerns, since he was well aware of the variability inherent with the 665nm and 590nm filters, and how the results are influenced by the sensors they are paired with. He agreed to do the conversion, even though he suspected it might be a bit more work, since he had to undo an IR conversion previously done by another company.

If you are contemplating a conversion, I strongly encourage you to reach out to the companies you are considering and gauge their willingness to entertain and respond to your questions, the thoroughness of their responses, the quality of their website material, and their overall attitude toward customer support. I was extremely impressed with Kolari Vision’s pre-conversion communications. Ilija was always available to answer my questions even on weekends and late night hours. Had I taken the time to speak with Ilija prior to choosing my original 665nm IR filter, I suspect I would have reconsidered this choice and stayed with the 720nm filter.

And since filters with the same rating (such as 720nm), from different manufacturers, can produce different results, reach out to others on the net regarding their experiences with different camera models, filters, and conversion companies. This will help you understand whether your particular camera and the IR filter from a given IR conversion company are capable of producing IR results that are satisfying to your eye.

So my D7100 was off for another IR conversion…

4) The D7100 / 720nm IR Combination

4.1) Custom White Balance – Oops!

Ilija quickly converted the camera and shipped it back to me within a week. It turned out to be quite a bit more work than he anticipated. Once I got my D7100 back from Kolari Vision, I was eager to test it out. Unfortunately, spring was not much further along in Pittsburgh, so decided to head back to Phipps Conservatory. Before doing so, I attempted to create a custom white balance setting, something very helpful to have relative to getting consistent IR results. The usual method of setting a custom white balance by “pointing your camera and filling the frame with a patch of grass on a sunny day” didn’t seem to work. I tried it numerous times and verified the steps via the manual, but I couldn’t get it to work. I tried increasing and then decreasing the exposure compensation, blurring the image, and every other trick I am familiar with, all without luck. I tried the same process with my D90/720nm filter and had no problem creating a custom white balance setting.

Recalling that the other conversion company had created a custom white balance by pointing the D7100 toward a lamp (I could see it in the custom white balance settings), I tried the same trick. Sure enough, I was able to create custom white balance settings using a halogen light, a regular incandescent bulb, and an infrared flashlight. For some reason that I have yet to determine, the D7100 needs an extraordinarily bright light source in order to focus with its IR filter. I am still doing some investigation as to the reason behind the inability to use the most common method of creating a custom white balance with the D7100. I will provide an update to the article if/when I get a solid explanation. It may simple be that algorithm Nikon uses in the D7100 to determine if the camera has captured a suitable photo for use as a custom white balance setting isn’t compatible with the amount of infrared light reflected by the grass. Since I shoot RAW most of the time, this wasn’t a deal breaker for me.

4.2) Kolari Vision 720nm IR Filter Performance

Once I got down to Phipps Conservatory, I was disappointed to see that they had switched the main garden court’s theme. Gone was the “Lady of the Garden” (as I nicknamed her), and in her place, was a set of mastodon bones formed from colored glass. They were appealing in their own way, but certainly not as beautiful as my previous subject. Of course, had I ever contemplated that I would be sending my D7100 back to switch filters and doing so many comparison shots, I would have created a more structured test case!

As I previously mentioned, each specific IR filter and camera sensor combination is going to provide somewhat different results from others. I took a good bit of time to experiment with different white balance settings in Lightroom. I found that my old Lightroom settings used with my previous 720nm filters on my D40X and D90, even starting with the custom white balance setting, didn’t seem to work very well with my Kolari Vision 720nm filter on my D7100. The traditional color swapping routine in Photoshop’s Channel Manager needed some tweaks as well. After reading some reports by other IR photographers touting the white balance superiority of Nikon’s Capture NX2, I decided to download a trial copy. While it yielded somewhat different results than Lightroom, I can’t say that the final processed photos from Capture NX2 looked better. After some experimentation, I was able to find a set of white balance settings in Lightroom and a Channel Mixer color swapping action in Photoshop that yielded consistent results for the D7100/720nm filter combination.

Note: If you are new to IR photography and/or have recently switched cameras/sensors, be aware that post processing requires a bit of experimentation and patience. It is made more complicated by the fact that any Channel Mixer settings you use are highly influenced by the starting white balance point. Unfortunately, even subtle changes in white balance settings in Lightroom or Adobe Camera RAW (if you are shooting in RAW), which are often difficult to discern on your computer monitor, can cause significant changes once you apply a Channel Mixer action.

5) The Nikon D7100 As An IR Camera

The D7100’s 24MP sensor provides a significant boost in detail beyond the D7000’s 16MP sensor, and the 12MP sensor DSLRs. As we all know, it is not simply the number of megapixels that determines quality, but rather the quality of those pixels. While I appreciate my D800’s 36MP detail, I have to admit that a quality 24MP sensor is just fine for most purposes.

And as Nasim points out, The D7100 handles noise very well. The D7100 is also a great match with the Nikon 16-85mm 3.5-5.6mm VR lens, arguably one of the best and most flexible DX lenses for IR photography. This lens been glued to each of my IR DSLRs since its introduction. If the Nikon 16-85mm VR lens is out of your price range, bear in mind that the humble and cheap Nikon 18-55mm 3.5-5.6 AF-S (VR and non-VR versions) lens produces excellent IR results. Since many IR shots are also taken at apertures between f/5.6 – f/11 with low ISO values in good lighting conditions, the advantages of FX over DX, relative to low noise at high ISOs and shallow depth of field, are somewhat negated.

You may wonder why I recommend the D7100 over the D5200 (also a fine camera and great value), since their sensor performance, as tested by DXO Mark, is very similar. I like the ability to access the D7100’s camera controls via external buttons, rather than having to dig through the D5200’s menu system. Having access to the Exposure Compensation button on the top of the D7100 is quite handy for IR photography, since the DSLRs do not always meter IR light as well as visible light. As such, I often find that I may have to make adjustments via the Exposure Compensation button (usually within +/- 1). In bright sunlight, the menu systems of most cameras such can be a bit tough for me to see, so I appreciate the D7100’s method of handling adjustments via controls more than that of the D5200. And since I have large hands, I also found that the D7100 was a bit easier to handle than the diminutive D5200. In light of these considerations, and the D7100’s sticker price of ~$1,200 (US dollars), I believe the D7100 is an ideal IR DSLR. And I couldn’t be more pleased with Kolari Vision’s IR conversion and customer service.

6) Summary

• For Nikon shooters, the D7100 is a great IR camera at a very affordable price. Its 24MP sensor does an excellent job relative to detail, noise, and managing IR light. The D5200 also represents a solid bargain if you are willing to live with a few trade-offs.
• Before deciding on an infrared filter, make sure you do your homework and determine how well each filter (from a specific manufacturer) works on your specific camera model. In my case, I realized I was taking a bit of a chance, since I was the first to have a D7100 converted to the 665nm IR filter. Don’t decide on an IR camera conversion using a filter until you have had the opportunity to see a few examples of photos processed with it. This is especially true if you are considering filters such as the 590nm or 665nm.
• Scour prospective IR conversion companies’ websites to get a sense for their level of knowledge, insights, and options. Make a few phone calls and gauge the responsiveness of the companies’ product support staff. Don’t sign on for a conversion without making sure that all your questions are answered via phone or email.

Update:
Since I wrote this article and others related to infrared photography, many people have emailed me with questions related to IR and advice regarding IR conversion services. Over the last few years, I have recommended Kolari Vision. Kolari Vision has converted four DSLRs for me. I have been very impressed with the quality of the service, turnaround time, value, and performance of the IR converted DSLRs. Ilija Melentijevic, Kolari Vision’s founder, has been especially patient and helpful in explaining the technical and nuanced aspects of converting and using digital cameras for infrared photography. Kolari Vision offers a full range of infrared, ultraviolet, and other specialized digital camera solutions and related filters.

If you have any IR conversion stories to share, please post them below.