Wratten 88 filter factor

[GraflexNut]

Looking to use do some sunrise infrared photography and general landscape, I have some film and a Wratten 88 filter I found lying around in a display case in my university (obtained with permission of course!). However, I have had trouble finding what filter factor the Wratten 88 filter has. I tried looking through one of the old scans of books about the filters but tbh it was all greek to me. If anyone has any advice that would be greatly appreciated! For reference, I'm shooting Rollei IR in a Mamiya C330 using a Series VI Wratten 88 Filter. Thank you all!

 

[AnselMortensen]

Using a film "similar" to Rollei Infrared (Aviphot), I used an R72 filter at EI of 1.
In. Bright. Sunlight.
Sunrise lighting?
You might want to do a bracketing test under the conditions you want to shoot to determine the proper exposure for your intended use.
Wratten 87/88/88A filters were tested with Kodak Infrared films/plates back in the day.
Rollei isn't particularly forthcoming about the specs of their film...and the IR sensitivity is NOT the same as Kodak's.
Test, and please report back with your findings!

 

[reddesert]

Filter factors for IR film usage are very dependent on the filter and the film in use, and the scene lighting. Especially because Kodak HS Infrared had sensitivity further into the near IR than any "IR" film you can get today, any filter factor that you look up has to be taken with a lot of caution.

The R72 filter that a lot of people use now transmits light redward of about 720 nanometers (hence the name).

If you look on page 70 of the Wratten filters handbook scan from Pacific Rim Cameras: https://www.pacificrimcamera.com/rl/03844/03844.pdf
it shows that a Wratten 89B reaches 50% transmission at about 720 nm, and a Wratten 88A reaches 50% transmission at about 760 nm, which is significantly further red. So roughly the 89B is like the R72 filter you can get today, and the 88A will transmit less.

My guess is that Rollei IR has just a little sensitivity redward of 720 nm, and with the 88 filter you'll get almost nothing. I would look for a filter like the R72 - you can get 720 nm IR filters inexpensively on ebay in threaded sizes, one of which should fit the Mamiya lens. I have used some of these inexpensive IR filters and they work.

 

[Patrick Robert James]

I used to know exposures by heart with HIE and Konica Infrared. That was a long time ago. There really are no "filter factors" that you will find for your combination since infrared is a different beast. You'll have to test.

According to the chart on Wikipedia, if accurate, the 88 passes wavelengths greater than 700 which would result in a little more light than an 87 (740) but slightly less than an R72. I doubt it is that significant, though it can be depending on the sensitivity of the film.

In reality, I doubt you can count on any of that information since there really isn't a standard. Filters can be named whatever. Also the filter you have might be old and not as effective at blocking non-infrared light as it once was. Again, you'll have to test.

Back when I shot a lot of infrared I preferred dark red filters as opposed to the opaque infrared filters. I was using SLRs though so I needed to be able to see and with your Mamiya that isn't a factor since you aren't looking through the filter. I still liked the tonality better with the red.

 

[Andrew O'Neill]

@GraflexNut, I believe the 88 has a factor of 64x, or 6 stops. I would only use that filter if there were a tremendous amount of IR energy about. Even then, the 64x might not be enough. You'd have to experiment... and of course, get back to us! But seriously, those extremely long exposure may not make it practical...or fun. I'd just get my hands on a cheap Zomei 720 filter. That is what I have been using for years. Works better than my expensive Urth 720!

 

[Mr Bill]

However, I have had trouble finding what filter factor the Wratten 88 filter has. I tried looking through one of the old scans of books about the filters but tbh it was all greek to me.

Hi, I generally consider the filter factor more a characteristic of the film being used rather than a standalone characteristic of the filter. As well as the specific nature of the light source and exposure meter in use.

My point is that you would ideally be looking at a FILM DATA SHEET for this information, and hoping that your specific filter is covered.

And it turns out that the Rollei infrared data sheet DOES list the 88A filter. You should look up the film data sheet yourself for more complete information, but when using a handheld exposure meter the filter factor is given as 16 to 32 times.