IR Hotspot - Lens Ratings

Obvious blemish or subtly diminished contrast - The infrared 'HotSpot' is to blame and it can ruin your photography. This page aims to demonstrate precisely how well each lens copes with IR in demanding lighting situations. The scores below (out of 10) show IR HotSpot intensity at 830nm & f/8. Click the lens links to see how that score varies through the apertures (& focal lengths for zooms).

Auto Focus

Manual Focus

CANON EF

NIKON F (AF-D)

SONY E (FE)

SIGMA (Various)

CANON FD

NIKON F (Non-AI F)

NIKON F (Non-AI K)

NIKON F (AI)

PENTAX PK

OLYMPUS OM

​​

M36

M39

M42

  • 6.2 - 50/1.4 (Yashica)

  • 8.9 - 55 /1.8  (Takumar)

  • 8.9 - 55/1.8 (Mamiya)​​​​​

  • 8.6 - 80/1.8 (Zeiss Pancolar)​​​​​

  • 10. - 200/2.8 (Zeiss)​​​​​

KONICA AR

MINOLTA MD

APS-C CROP (NOT FULL FRAME)

CANON EF-S

  • 9.7 - 24/2.8 [STM]

  • 7.9 - 18-55/3.5-

  • 8.2 - 18-55/3.5- [2]

  • 8.0 - 55-250/4.0-

  • SONY E ....

  • (AI-S) ...........

  • 24 ..............

  • 24-70 .........

  • 5.7 ..............

  • _._ .............

  • /2.8 ...........

  • /3.5- ..........

  • (Sigma.......

  • [P] ..............

  • [B] .............. 

  • [C] ..............

  • [M] .............. 

  • [S] ..............

  • [2] ..............

  • [STM...........

  • [SF] .............

Key

Scores

What these scores might mean for your photography. The chance you'll notice a hotspot (HS) and how reliable / consistent the contrast is likely to be:

Perfect

- Extremely Good

- OK - Good

- Meh

Disappointing 

- Poor

- Bad

- Very Bad

- Extremely Bad

- Ridiculously Bad

- Unusable

- (HS: 0%)

- (HS: 1%)

- (HS: 5%)

- (HS: 10%)

(HS: 20%)

- (HS: 40%)

- (HS: 60%)

- (HS: 80%)

(HS: 90%)

(HS: 95%)

- (HS: 99%)

Manufacturer / Mount

Lens Type

Prime (Focal length)

Zoom (Focal Range)

HS Rating

HS Rating - Coming Soon

Max. Aperture (fixed)

Max. Aperture (Varies)

Manufacturer

Premium Lens

Budget Lens

Compact Lens

Macro Lens

Stabilization 

Version Number

Stepping Motor

Soft Focus

SCORE NOTES

 

The Good & Bad

The lens scores you see above are taken at f/8 due to it being a commonly used aperture (especially for landscape photography). Lenses almost always perform better at wider apertures so if you're going to be using those settings more often the lens will do better than stated. Equally, if you're going to be using smaller apertures (higher numbers), then the scores will likely be worse than stated. All the lenses listed above are tested at every aperture, so if you want to see exactly how they score throughout the aperture range click on the link for that lens.

Lower Wavelengths & Colour IR

Lower wavelengths of infrared show less intensity from the hotspot issue. This is due to some of the light coming from visible light, which is unaffected. This works logically when processing like a b&w image. However, the hotspot can appear worse when processed as a colour image. For example if your foliage is yellow and your sky is blue, the hotspot can show up as yellow in the clouds (where it would otherwise be blue or grey). Once you notice this issue it's hard to ignore it and even harder to fix than a b&w image.

Specific Lens Versions

While making this page I have noticed that lenses with the same markings can have different optical designs and especially coatings. I will start to retroactively add more details about the lenses that I test so that results can be more reliably reproduced. The Konica section has been fully fleshed out with details about versions, so check that out if you're curious.

Hotspots Are:

  • Reflected infrared light, "mostly" concentrated in the middle of the frame (see above examples)

  • An effect that's always present to some degree in "normal" (non-specialist IR) lenses

  • Caused by the lens (although initially caused by the reflectivity of the multiple sensor filter layers)

  • Almost always amplified when stopping down the aperture (higher numbers / smaller sizes)

  • A reflection of light intensity from inside the frame

Hotspots Are Not Caused By:

  • Highlights outside of the frame (Not reduced by using a lens hood)

  • The Camera body (although it is related to the sensor, all digital sensors are reflective)

  • Conversion (not made better/worse by removing the hot mirror)

  • Exposure time

  • External filters

  • Internal filters (although AR coatings do exhibit improvements on internal filters **)

  • Adapter (if you use one, no matter how non-reflective it is, it won't cause this specific issue)

  • Viewfinder (Mirrorless cameras don't suffer from 'light leaking', but DSLRs can / not related to IR hotspots however)

**Anti-Reflective Filter Coatings

Anti-reflective (AR) coatings on infrared filters can help to reduce the hotspot intensity. In my experience this is only noticeable when the coatings are applied to the internal filters. External filter coatings had no obvious effect on the lenses that I tried. However, it's worth noting that this was tested before I started this more accurate rating system. Click here to see how much effect internal AR coated filters had for me (using this same scoring system).

Perfection Achieved

Until recently I didn't think that it would be possible to see a 10/10 score with a normal lens, but some of the Konica telephoto lenses have reached this level. This means that the brightness of the background in the center of the image is as it would be if the light was not there. Lenses will almost always produce a hotspot to some degree in IR. This is something that commonly affects newer, wider and faster lenses more, but there are no set rules for this so specific testing must be done to be sure. 

 

Correction Partially Possible

Although hotspots are concentrated in the center of the frame they effect the entire image to some degree based on where the brightest parts of the image are located. This damages the contrast in unpredictable ways throughout the frame. Although you can reduce the most obvious effects from a hotspot in post this will damage image quality and cannot be fully corrected for.

My Infrared Photography Galleries

Edward Noble

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