Lens Review - Konica Hexanon AR 40mm f/1.8

40mm pancake lenses make for a nice, compact system with mirrorless cameras (even with the necessary adapters). When adapting to older 35mm SLR lenses there are many options out there too. If you want something faster than f/2.8 however the choices go right down and if you're on a tight budget too then it might just be this Konica you're looking at. I managed to pick this one up for £40 on ebay. Although the price seems to be going back up a bit now I've seen them go for as little as £20. So the big question is; can it perform any better than it's measly price point?..

      Stats
Mount: Konica AR
Adapts to DSLR: No
Adapts to Mirrorless: Yes
Focal Length / Angle: 40mm / 56°
Lens Construction: 6 elements in 5 groups (1 aspherical)
Aperture range (f stop): 1.8 - 22 (Automatic)
Aperture Blades: 6 (straight)
Aperture Ring: Yes
Focus Mechanism: Manual
Focus Ring: Manual / Attached
Minimum Focus Distance: 45cm
Max Reproduction Ratio: 1:7
DoF Scale: Yes
IR offset markings: Yes
Filter Size: 55mm (metal)
Dimensions (mm): 27 x 46
Weight (g): 140
Body Material: Metal
Dust & Moisture Sealed: No
Country/Year: Japan / 1979-1989
Price (New/Second Hand): - / £30-60
Accessories: Unknown

     IR Quality / Hot Spot
Here's a test I came up with to illustrate how much each lens is afflicted with the infra-red hot spot issue. The test involves taking images at every aperture, whilst facing away from the sun, having a clear blue sky in the centre and filling the rest of the frame with well lit foliage (you can read more about the idea here).

These shots show the Konica 40mm to be an extremely good IR performer when it comes to contrast and hot spot issues. Other than the widest aperture showing a fairly heavy vignette (which kind of looks like a big hot spot) it's usable in any aperture for 'normal' use. If you push up the exposure a lot while using the smallest apertures then it's possible to show up a large light disk, but this is so subtle in normal exposure levels that I don't see it being a big problem for most people. The typical 'centre spot' doesn't show up at all on the 850nm filter.

Here is a test scene shot using the B+W 093 filter. This has a 50% transmission at 850nm and lets through only a tiny bit of visible light (almost pure infra-red).

Here is the same test using the Heliopan Red filter (similar to a 600nm filter/conversion):

These next two images are shot at the smallest aperture (f/22), but this time with the exposure compensation set to +3, for each filter. This shows the extreme worst case and it's clear that the 850nm IR filter is getting a bigger hit in regards to hot spot. The red filter only had an issue in the blue channel, but in the 850nm filter the effect was fairly even spread over all three channels.

Overall the Konica 40mm is a stunning lens in IR. It's easy to avoid any major issues with hot spot unless you shoot a lot at f/22 (possibly f/16 too) and need to shoot high-key for any reason, other than that it perform extremely well indeed!

   Scores (general)
Center sharpness (f/1.8): 9/10
Center sharpness (f/8): 9/10
Corner sharpness (f/1.8): 1/10
Corner sharpness (f/8): 8/10
IR - Hotspot: 9/10 (Almost Nothing)
IR - Colour Hotspot: 9.5/10 (miniscule)
Distortion: 6/10
CA (Chromic Aberration): 6/10
Axial CA: 5/10
Veil Haze: 2/10
Vignetting: 8/10

     Conclusion

The Konica 40mm is a great little performer, regardless of it's price and infra-red this lens is even more impressive. Producing some of the cleanest colour IR and pure IR image quality that I've ever seen. If you have an IR or full spectrum converted Sony A7 then you can't do much better for a small, high quality and extremely good value lens. If you're using it on a crop mirrorless camera then I still think it makes a great purchase. It then makes a 60mm f/1.8 lens that loses what little imperfections it had in the corners anyway, so I would still highly recommend it.

On full frame it has to be one of my all-time favourite lenses and not just because of how cheap it is. I find 40mm a great walk-around, or travel lens too. I  and would happily only take this away with me considering how versatile it is, making a pretty neat and portable combo with the A7 series cameras. It's almost as small as the FE Zeiss 35mm f/2.8 lens (including the adapter), while being over a stop faster, has almost comparable image quality and a can be picked up for a tiny fraction of the price!

It may not have the prettiest bokeh if focusing over 2m (neither does my 50mm f/1.2) and the 55mm filter size can be a little annoying, but for the price it deserves about double the score I'm about to give it.

Overall Score:

10/10

   IR Samples

Here are some colour infra-red images, taken with the Konica 40mm f/1.8 lens & the Hoya R25A (Red) filter (on the full spectrum Sony A7). This is equivalent to about a 600nm conversion. All image, accept the first one, are processed using the 'false colour' technique:

f/5.6 

f/8 

f/5.6 

f/1.8

f/1.8

f/8 (Lens Blur, Photoshop)

Here are some black & white infra-red images, taken with the Konica 40mm f/1.8 and the B+W 093 filter (also on the full spectrum Sony A7). This filter has a 50% transmission @ 850nm.

f/5.6  

f/8 

f/5.6

 f/4

 f/1.8

f/8