Using the Tokina atx-m 11-18mm F2.8 E for infrared photography
What is infrared photography?
Infrared photography is about taking photos with full spectrum modified cameras. What's different with an IR camera? The way sensors of digital cameras technically work, allows them to catch a broader part of the spectrum of the light than our eyes can see. Including the wavelengths of infrared and UV light. As we humans are not capable of seeing infrared rays and as IR/UV light lowers the image quality, there is a filter stack mounted on your camera sensor to block those unwanted wavelengths. We don't see them so we just don't need them on our images lowering the sharpness etc. Additionally, photography lenses can only process visible light in a proper way, as the different wavelengths of red, green and blue are getting refracted by the different glasses used in the lens.
So, the sensor can catch IR but we just don't need it in most areas of photography and also most lenses are bad at processing IR rays. Exceptions are made - you may have heard of IR capability being important for surveillance, wildlife or astro imaging cameras.
Why IR photography?
So, IR photography is pretty much just making the invisible light visible to the human eye and you only get that with a full spectrum-modded camera and some filters. There is a screw on front filters that go in front of the lens and there a clip-in filters that go behind the lens. The filters block a certain part of the visible light, leaving you with infrared light only. Depending on the wavelength, a very high filter value will leave you with a black and white image only (850 nanometers or above), while lower values (like 590 nm) will get you a mix of infrared and visible light, which often gets you very interesting results.
All the plants, grasses and trees - so basically anything with chlorophyll in it - will look different on an infrared image, depending on the wavelength of the used filter. Leaving houses, roads, basically any other non-plant materials as it is or partly in black and white, again depending on the filter. IR just looks otherworldly and cool. It's always a pleasant surprise.
Some filters like the IR Chrome need very basic post processing while narrower banded filters like 590nm and above will need you to set up an IR white balance profile and do a simple channel swapping in Photoshop. Additional color and brightness corrections may be needed depending on your personal taste.
Why it's difficult to find good IR lenses and why the Tokina atx-m 11-18mm F2.8 E is a great choice?
Speaking of finding a good infrared lens, the Tokina atx-m 11-18mm F2.8 E is a great find because it works pretty well for IR. Mounted on a full spectrum modified Sony a6000 the lens performs perfectly fine throughout the whole zoom and aperture range. Using lenses for infrared photography often comes with a problem - a lot of lenses will get you a hot spot in the image. So what exactly are we talking about here? An IR hot spot is basically a bright spot in the middle of the images that can't be removed in post processing. Hot spots often come along with color shifting and any kind of uneven distribution of brightness within the image. Some lenses just can't deal with IR light as explained before, which will give hot spots, but the Tokina atx-m 11-18mm F2.8 E really shines here. I did not experience any issues with the lens, no matter which focal length and aperture I used - it's a perfect fit for infrared photography.
My experiences with the Tokina - sharpness, zoom range, optical quality
11-18mm is a very useful zoom range for landscape images in general. Starting at f/2.8 the lens works well also in low light situations while keeping the ISO at a reasonable level that still looks nice. The lens is super lightweight, you don't really notice you got in on you, so am taking it with me all the time. No problem on longer walks or hikes when weight really matters. The lens is super well-made and very sturdy. It even has a USB port so it's ready for future updates. The filter thread is well made and as it is only 67mm diameter so you will save some money as you can buy low diameter IR filters instead of needing the pricey bigger ones.
The auto focus is very fast and always accurate - even with an infrared filter attached the focus is always on point! Many other lenses struggle here and need manual focusing with IR but the Tokina just works like it was mounted on a non-modded camera. The zoom range is pretty useful since 11-18mm is quite a lot when talking wide angles. I included a picture showing the difference between 11 and 18mm and as you can see it's quite a lot. So, in everyday (and) infrared photography the zoom range comes in very handy.
The lens shows basically a great sharpness throughout the whole zoom range, which is quite a surprise in IR photography. Most wide angle zoom lenses struggle with the sharpness on the long end of their range, so I included a test at 18mm with different apertures. As you can see the leaves of that tree in the upper right corner of the image already show a decent sharpness at f/2.8. Remember we are talking IR photography here and we are shooting wide open. I wouldn't hesitate using the lens wide open at f/2.8 at all focal lengths all the time. Stopping down to f/4.0 increases the corner sharpness to a nice level and jumping to f/6.3 gets you even more sharpness. It's pixel peeping since the sharpness is already good at f/2.8 so there is just not much room left for increasing as things look great already in the extreme corners of an APS-C lens. Stopping down to f/8.0 is the perfect spot with the Tokina 11-18mm for IR photos if you are looking for perfect corner sharpness within the scope of possibilities of this lens. I'd use f/8.0 all the time when there is enough daylight. Stopping down more you can clearly see diffraction starting to lower the sharpness which is a completely normal process with every lens. So, f/8.0 definitely is the sweet spot here for IR but everything between f/2.8 and f/8.0 will look great.
Final thoughts
By the way the Tokina atx-m 11-18mm F2.8 E gets you even better results on stock cameras but as this review is about IR photography - if you are looking for an affordable lens for IR, look no further than the Tokina atx-m 11-18mm F2.8 E. Lightweight, super well made, affordable, easy to handle and to carry around, great and fast AF and it has perfect IR capabilities. Takes filters of all IR wavelengths very well, no matter if lens filters or clip in filters - everything works great.
