Flare with CV 21/4 and Efke IR

[kossi008]

Hi Folks,

I have tried the search function and found variuos statements that the CV 21/4 is not very prone to flare. Well, this might be true w/o filters, but I found some nasty flare spots when shooting b/w w/ yellow or orange filters already.

But last weekend I discovered the mother of all flares (excuse the stupid wordplay) when using Efke IR 820 film with a Heliopan RG715 filter. It looks like this, and the sun was not even inside the frame (see attached picture).

I am using the original short hood, which is bascially ineffective when screwing on any 39 mm filter. Should I get the bigger optional hood? Something else altogether? Any hints are appreciated...

Thanks,
Georg

 

[Sparrow]

Maybe there’s something wrong with it? My copy hardly flares at all, this is about as bad as I get, misty day, sun in the frame, orange filter and the small hood, the haze was there that’s not veiling flare

link

 

[rxmd]

In IR photography it's not uncommon to get flare problems that you don't have in visible light, with many lenses. The reason is usually that coatings are designed for visible light and may be ineffective at longer wavelengths. In general, you can't draw conclusions from a lens' flare behaviour in visible light to how it will behave in infrared; you can get all sorts of flares, hotspots, ghosting, what have you, especially when shooting in the general direction (not even "into") the Sun. I haven't shot IR with mine, but from your shot it appears that with the CV 21/f4 you have to be especially careful in this respect, (just like with ultrawideangles in general).

I don't think there's anything wrong with your example, it's just that IR is a completely separate set of applications for a lens.

I wouldn't automatically assume a Biogon or Elmarit 21 or Super Angulon to be show the same flare behaviour in IR as in visible light, either, other qualities of the lens notwithstanding. Concerning flare in general, I find the 21/f4 to be quite flare resistant; you may get and/or provoke flare in some situations, but I would wager that you can find such situations for any lens, especially in ultrawideangles. The larger original hood may be a good idea. Lens hoods are recommended for IR photography in general, and with an ultrawideangle they appear to be particularly important.

Philipp

 

[Sparrow]

That would make sense, once the wavelength was over 4x the thickness of the coating there would be no effect

PS thinking about it, it could even amplify some wavelengths

 

[mr_phillip]

rxmd's post makes a lot of sense, as does the suggestion to buy the optional larger hood.

It could be your filter that's the culprit though. Flare is always more likely when using filters anyway; partly because you're introducing another set of glass-to-air surfaces, partly 'cos filter glass/coating quality is often lower than the lenses they're attached to, and partly because you're reducing the efficiency of any built-in hood by shifting the first effective glass-to-air surface forward by the depth of the filter. Obviously any marks on the filter glass will only make things worse.

For what it's worth I've found the 21mm Skopar to be remarkably flare resistant, even when using filters (I mostly use B+W filters). I've not shot true IR with this lens, but have shot a fair amount of Ilford SFX using a B+W 093 filter and haven't seen any signs of flare, even though I'm relying on the built-in hood only.

 

[kossi008]

That would make sense, once the wavelength was over 4x the thickness of the coating there would be no effect

PS thinking about it, it could even amplify some wavelengths

Now I think you're taking things a little too far. The Film is called Efke IR 820 because the sensitivity is going out to 820 nm. While the lens coatings are surely suboptimal in this range, it's not as far away as you suggest...

 

[tritiated]

I really like how the picture looks! The flares add something

 

[kossi008]

rxmd's post makes a lot of sense, as does the suggestion to buy the optional larger hood.

That's actually what I'm asking: should I buy it, i.e., has anyone any experience with the kind of shooting conditions I was referring to, and whether that hood is effective? Otherwise, if I have to shade the lens with a piece of carton or some such anyway, I might just pass by the hood altogether...

For what it's worth I've found the 21mm Skopar to be remarkably flare resistant, even when using filters (I mostly use B+W filters). I've not shot true IR with this lens, but have shot a fair amount of Ilford SFX using a B+W 093 filter and haven't seen any signs of flare, even though I'm relying on the built-in hood only.

Hmmm... this is doubly interesting. I usually shoot w/ B+W filters, too, but I can find some of the central flare spots with those and the standard hood as well... I did some preliminray experiments with the Skopar and SFX200 and a B+W 092 filter taped to the hood. Vignetted like hell, of course, but no flare problems...

Now what's really intriguing: you shoot with SFX200 and B+W 093? As that one is the RG830, the film should have hardly *any* sensitivity there. I have always been using the 092 (RG695) because I wouldn't even have thought the other combo works at all... what kind of EI do you get?

 

[kossi008]

I really like how the picture looks! The flares add something

Thanks for the flowers. I DO know how to get that effect if I want it now... but I was wondering how to NOT get it...

 

[Sparrow]

Now I think you're taking things a little too far. The Film is called Efke IR 820 because the sensitivity is going out to 820 nm. While the lens coatings are surely suboptimal in this range, it's not as far away as you suggest...

I probably am, but looking at the light reflected off the coating I see bluish/violet which would suggest the coating is optimised around 560nm a lot higher than the film. At some point the frequencies will become constructive and when they do you’ll see big time flare if the film is sensitive at that frequency, how would you describe the shot you posted?

 

[joachim]

I probably am, but looking at the light reflected off the coating I see bluish/violet which would suggest the coating is optimised around 560nm a lot higher than the film. At some point the frequencies will become constructive and when they do you’ll see big time flare if the film is sensitive at that frequency, how would you describe the shot you posted?

Hi Sparrow,

You were right on the money. The multi layer anti-reflective coatings typically employed on photographic lenses amplify reflections in the IR range. Look for instance at http://www.photofilter.com/images/2005afig1.jpg , which compares the reflections of a single coating and the
Hoya Super HMC coating. It shows clearly that for 750nm the HMC flares more than twice as much as the single coated filter.

I have read similar complaints to the original poster's question about the Pentax SMC 24/2. It becomes pretty prone to flare in IR photography.

In IR photography it is often better to use single or un-coated filters than the MC varieties and typically these IR filters are not offered in multi-coated.

Hope this helps.

 

[kossi008]

@ Sparrow:
Ooops, sorry for not believing you in the first place.

@ joachim:
Thanks for clarifying this... so I'll have to shade better, I guess... In any case, the filter is not HMC-coated, but the lens is, right?

 

[joachim]

@ Sparrow:
Ooops, sorry for not believing you in the first place.

@ joachim:
Thanks for clarifying this... so I'll have to shade better, I guess... In any case, the filter is not HMC-coated, but the lens is, right?

At least some of the surfaces of the lens will be multi-coated of some sort. With most lenses you see different coloured reflections on different surfaces. So each of these surfaces is differently coated.

By the way, it is possible to get multi coatings which would not have the problem of high reflections in the IR range. These are typically not employed on photographic lenses.

 

[rxmd]

In any case, the filter is not HMC-coated, but the lens is, right?

Well, the lens is not *H*MC coated (that's Hoya's in-house flavour of multicoating) but it is certainly multicoated, just like practically all modern lenses. Various coatings tend to behave differently, too.

Geometrically the 21 hood is big, but it appears to be pretty much the optimum for a square hood. It also provides a good base for attaching further pices of cardboard with sticky tape for further shading. In the meantime you might find someone who has an account for http://www.lenshoods.co.uk/custom.php to print yourself a paper hood. If you've got the sun in the frame no shade will change anything, of course.

Philipp

 

[Sparrow]

@ Sparrow:
Ooops, sorry for not believing you in the first place.

@ joachim:
Thanks for clarifying this... so I'll have to shade better, I guess... In any case, the filter is not HMC-coated, but the lens is, right?

It’s OK I don’t have any experience, just reasoning with what little knowledge I have, of colour that is not optics.

 

[kossi008]

@rxmd: Do you happen to know where to get the square hood in Germany? I can't seem to find it, as Mundus has it listed as "not currently available"...

 

[rxmd]

@rxmd: Do you happen to know where to get the square hood in Germany? I can't seem to find it, as Mundus has it listed as "not currently available"...

To be honest I don't know. Ringfoto has it on their Voigtländer page for 75 EUR, but their dealer list is singularly unhelpful and seems to include every corner minilab on the planet.

EDigitech has it for 79 EUR and DNET24 has it for 65 EUR but I've never had any dealings with them.

Robert White in the UK has it for about 35 GBP (45 EUR) and there you could get it without paying import duties. Also he's a sponsor here at RFF.

Philipp

 

[joachim]

To be honest I don't know. Ringfoto has it on their Voigtländer page for 75 EUR, but their dealer list is singularly unhelpful and seems to include every corner minilab on the planet.

Individual small dealer ships can become a Ringfoto member. Each of them should be able to order it in for you. At least that was how it worked in the 80ies and 90ies. I do not expect this dealer list to be unhelpful.

 

[mr_phillip]

you shoot with SFX200 and B+W 093?

Oops, slip of the brain. You're quite right, it's a 092 I use.

 

[kossi008]

Oops, slip of the brain. You're quite right, it's a 092 I use.

Just being curious...