timballic
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 Infrared and alt lenses (on A7) | |
Spurred on by the thread about how quiet the Alt forum has become, I thought I\'d share some of my experiences in Infrared and Alt lenses.
For several years, I\'ve been using a Canon 40D with a 780nm conversion, (which I did myself, with a lot of advice from an IR forum member) plus EF 17-40/4 L, which makes a very good IR combination (780nm, for purely black and white, \"traditional\" IR.) I wouldn\'t do another conversion myself, because of the difficulty in getting the IR filter critically micro clean....the rest of the conversion was a cinch by comparison.
However, having changed from Canon to Sony A7 for colour, just over a year ago and loving it, I now find this combination like carrying a brick! (I do have health issues, which makes this worse.) Also, I love the tilt screen of the Sony, (though fully articulated would be even better) and I find the 17-40mm on APSC not quite wide enough for my style.
I\'ve been assessing the merits of getting another A7 body and getting it converted to IR. The biggest question has been finding suitable lenses to use on it for IR.
Many/most here will know that in IR, lens performance changes from visible light performance. Many lenses produce a central \"hot spot\", and sharpness is generally worse. (Both MaxMax and LifePixel have articles on these.)
For some reason, I\'m less critical of corner to corner sharpness in my IR photography, than I am for colour....don\'t know why. So, in anticipation, I\'ve got myself a \"used, as new\" FE 24-70/4 (which I can always sell if it doesn\'t work out), but I also want to find which of my alt lenses work well in IR.
Using my converted 40D and adapters, I\'m starting to do some testing.
There are several other lists of these on the web, though not all in agreement. (Generally hot spots are worse using IR filters and long exposures on unconverted cameras)
First my OM lenses: NB. I\'ve edited the list for performance on the A7 (tends to show more problems than the 40D did.)
OM 21/3.5 MC A complex Hot Spot see later post pg2 #12(need to compare with an early SC version)
OM 24/2.8 SC No hot spot throughout aperture range
OM 28/3.5 SC Ditto
OM 28/2 MC Unknown
OM 35-70/3.5-3.5 MC (The tiny one) Hot spots at F22 and 16, none at F11 or wider (most obvious wide 35mm end)
OM 100/2 MC Ditto to 35-70
OM 75-150/4 MC No hot spots throughout range
OM 200/5 SC Ditto
However, quite apart from hot spots. I\'ve been surprised by the large difference in sharpness between the single and multi coated OM lenses in IR. The 21 and 24mm look quite soft (so different from their performance in visible light,) whereas the single coated 28/3.5 and 200/5 stand out for their clarity and sharpness in IR. However, I haven\'t got both single and multi coated versions of each FL to compare.
Probably, if you\'re thinking of getting OM Zuiko lenses for IR, the single coated versions will do better!
I also tried my CV lenses:
Voigtlander 20/3.5 Color-Skopar II Bad \"Rainbow\" hot spot throughout range, see later post pg2 #7
Voiglander 58/1.4 Nokton II Very poor IR performance re hotspot from F8-22, f5.6 and wider, may be just useable.
I\'m also going to test my MC/MD lenses, (with an adapter with glass element. Hopefully the element won\'t affect the results. )
(To come):
MD 24/2.8 (last version ø49) Bad diffuse central hot spot throughout range
MD 35-70/3.5 (3rd version) Hot Spot from F8 worst around 50mm
MC 58/1.2 (Ver 2. I think, with scalloped metal focus ring)....
MD 100/2.5 (last version)....
MD 100/4 macro.....
MD 200/4 (next to last version)...
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