UV on film - How to focus?

[Fandyus]

The idea of shooting UV on film seems to be perhaps a bit controversial here, but I still like it. It may not be super practical or advantageous (at least in UVA), but I like the nature of b&w film and I have Foma made filmstocks available to me for quite cheap. I think flower pictures could be very interesting if recorded on an analog medium. Or even landscapes, anything.

The one question is, how to focus?

 

Obviously, film cameras have no live view and I for sure can't see UV. Is there any rule I could use to focus on objects with at least some accuracy?

 

Thanks.

[Andy Perrin]

Set lens to infinity, stop down, and don't take pictures too close to the camera? Honestly most of the UV film stuff on here seems to be landscapes and I think that's why!

 

I know nfoto did film UV of flowers once, maybe she'll have better advice.

[Fandyus]

Just now, Andy Perrin said:

Set lens to infinity, stop down, and don't take pictures too close to the camera? Honestly most of the UV film stuff on here seems to be landscapes and I think that's why!

 

I know nfoto did film UV of flowers once, maybe she'll have better advice.

Thanks. We'll see.

[Fandyus]

I actually have one, slightly insane idea. Perhaps I could equip my full spectrum camera with a wide angle lens, akin to the human eye to some extent and put it up to the viewfinder. I might be able to see what's going on.

[Andy Perrin]

You could also put the same lens on your digital camera, and make yourself a table of "infocus distances" for that lens, then use it with the film camera with the same lens.

[Fandyus]

1 minute ago, Andy Perrin said:

You could also put the same lens on your digital camera, and make yourself a table of "infocus distances" for that lens, then use it with the film camera with the same lens.

That's what I originally thought I should do, problem is that cameras have slightly different flanges, and especially now, that I will be using the a6000 that becomes troublesome. The adapter for the a6000 is way too short, I have already tested it before I sent the camera off Germany for conversion. It's good because it guarantees infinity focus in UV, but for this specific purpose it makes it useless. I will also be selling the old Canon once I have the a6000.

[DaveO]

try this reference

https://www.medicalphotography.com.au/Article_01/07.html

[dabateman]

Yes its a pain to not have live view.  Thus why I switched to instax film for some of my crazy film shots.

Each of my lenses seem to be a little different for UV than visible and depending on focus distance.  My UAT lens,  known for low drift needs a small adjustment at close focusing distance. 

My 60mm macro seem to be designed for similar focus at UVC and visible.  For UVA and UVB the focus point is way different.  But its design for those two imaging wavelengths for fingerprint detection. 

[ulf]

This problem for film based cameras is the same as for the more common IR film photography in NIR.

That was at least partly solved on the lenses with the IR mark, often a red coloured dot or line among the focus index reference line(s)on the lens body near the distance scale.

That dot/line showed the offset adjustment needed to compensate for NIR compared to the VIS focus setting.

 

You can just mark a point on the lens with an offset that show the needed UV adjustment that you find in the live view.

With the too short adapter you juts have to markup the correct VIS point too, beside the UV point.

The offset(s) will get you a reasonably good hint of the  adjustment needed

[nfoto]

You could use a view camera .... (in fact, done that myself so idea is not that far-fetched).

 

For my film-based UV work with a 35mm format SLR, I used the UV-Nikkor which is parfocal UV-visible. Failing access to such lens, using the IR mark on the lens should improve UV focus accuracy and stopping well down nail the focus in addition. One just have to make a test set up and keep copious notes.

[Wayne Harridge]

2 hours ago, nfoto said:

You could use a view camera .... (in fact, done that myself so idea is not that far-fetched).

 

For my film-based UV work with a 35mm format SLR, I used the UV-Nikkor which is parfocal UV-visible. Failing access to such lens, using the IR mark on the lens should improve UV focus accuracy and stopping well down nail the focus in addition. One just have to make a test set up and keep copious notes.

 

I wonder if anyone has tried coating a view camera focussing screen with a fluorescent substance?

 

By the way, the IR focussing mark on a lens must relate to a specific IR wavelength, I've noticed significant differences in focus going from a 720nm --> 950nm filter.  Most lenses with IR focussing marks were probably designed in the film era so maybe related to the spectral response of films of that era (Kodak HIE?).

 

[nfoto]

Kodak IR film had  a spectral response < 900 nm. Digital IR has allowed us to explore more of the NIR. Plus getting rid of the hideous highlight glare from the Kodak film due to its lack of anti-halation backing.

 

The further you venture away from the visible light with any non-specialist lens, the more focus correction is likely to be required. You might end up with a lens that cannot focus to infinity, for example.

 

 

[photoni]

do you have graphs of the spectral sensitivity of some orthochromatic and panchromatic photographic films?

a thousand thanks

Toni

there was In a post with an image last year, but it was deleted

[nfoto]

Try this overview,

 

[Fandyus]

Thank you everyone for your tips thus far.

[photoni]

Many Thanks @nfoto

the wet plate is 325 to 510nm.
When I tried the fomapan 100 + BG25 + BG18 it was similar but not the same.

 

P.S. missing from your list: Rollei Ortho 25 plus (380 to 560 nm)

for extreme UV there is also the BERGGER PrintFilm in sheet format sensitive from UV to 500nm

 

 

my italian dealer is

http://www.puntofoto.it/shop.asp?id_cat=42&id_subcat=227

 

 

[photoni]

17 hours ago, Fandyus said:

Obviously, film cameras have no live view and I for sure can't see UV. Is there any rule I could use to focus on objects with at least some accuracy?

maybe you can use a Nemo 365nm flashlight with ZWB2 to focus with the lens fully open and then close at f/11 ?!?!

[nfoto]

Using a Nemo or similar torch will work equally well with a film system to allow focusing in UV.

[ulf]

18 minutes ago, nfoto said:

Using a Nemo or similar torch will work equally well with a film system to allow focusing in UV.

Am I missing something here?

You cannot look into or see the 365nm through the lens and finder.

 

Then there must be test exposures logging the lens distance settings, followed by processing the film.

For close ups a long ruler might be a good test target to compare with the actual settings on the lens

[nfoto]

My memory fails and you are correct. I used obviously lens without filter to focus, then add the filter (flip-up holder). As I mainly used the UV-Nikkor back then, there was no focus shift to worry about.

[Akira]

Specialized lenses like UV-Nikkor or Coastal 60mm are very expensive, but older EL-Nikkors 80/5.6 and 105/5.6 (chrome bases) can be much cheaper.  They show surprisingly little focus shift when used with Hoya U-360 filter: you can focus at the flower visually and are good to go.

 

With the lenses that shift focus in UV, I had to measure the amount of the shift.  Then, I mounted the camera either on an universal rail with the scale or a focusing rail to focus visually and then shift the camera/lens according to the measured value.

[Andrea B.]

Fandyus, using film for reflected UV is not "controversial" here. It is rather that nobody wants to go to the trouble any more now that we have digital.

 

We do have a Film tag, so what little we have about film can be searched for. (I just added the Film tag to this topic.)

 

Anybody who experiments with UV film and wants to write a tutorial is quite welcome to do so. We'd love to have one.

[photoni]

@Fandyus initial question was how to focus with a normal SRL with film

Assuming you want to use Baader U2 or (UG11 + S8612) or (ZWB1 + QB39 ... even if it's not the same)

the most logical thing since we don't see with Baader U2 or UG11

is to focus with a stack BG25 or BG3 + S8612

then change the filter and use the f11 aperture.

.

I love making still life with flat film, I think I buy the BERGGER PrintFilm, I saw some good results from a friend, then I have to buy a large diameter ZWB1 for my old Petzval and Planar

.

.

To get a precise measure of the focus shift you can use this pyramid

Then mark the shift of focus on that particular target with a blue point !!!

i think a Nemo UV flashlight is likely to help exclude the red part

[enricosavazzi]

I started in NIR and NUV imaging with a Nikon D70, which is a DSLR without live view. The only way to make it work was shooting preferably with the camera on a tripod, focus in VIS through the optical viewfinder, then mount a UV-pass or IR-pass filter on the lens and shoot away. Nikon used to have two sizes of a swinging filter holder that made it faster to insert a filter in the optical path in front of the lens than screwing/unscrewing it, this did help. Some sort of filter cassette in front of the lens, or between lens and camera in the case of a mirrorless camera, could also work.

 

If I knew my lens had a significant "focus shift" beyond either end of the VIS spectrum, I would stop down a couple of stops to let DOF "absorb" the focus shift.

 

Sometimes I tried to compensate for focus shift in close-up photography by guesstimating the focus shift and somewhat compensate it away by manually shifting the focus in the opposite direction, but it never worked too well.

[nfoto]

Nikon delivered the AF-1 filter holder with the UV-Nikkor. It was very practical and this setup in combination with the UV-Nikkor might have spoilt me to treat UV shooting on film a breeze. As long as I stayed clear of Kodak IE Infrared Ektachrome, there was no IR "contamination" to worry about.

 

The holder could take gelatine sheets, ordinary filters with 60mm (sic!) threads, or the Nikon "FF" UV bandpass filter (approx. Wratten 18B I'm told), the latter being inserted into a separate holder that screwed into the AF-1.

 

By the way, the Nikon "FF" filter on digital is even more atrocious than the B+W 403, in that it leaks IR in massive amounts.