Getting up and running with some daylight images...

[CharlesS]

Good afternoon all:

 

After establishing that my existing inventory of Nikon AF lenses really don't function effectively with anything remotely like suitable exposure times, I found a 1970s or 1980s -era 50mm f/1.8 manual focus ai lens in decent condition from B&H, and thus far, I think I'm getting the hang of composing images and getting decent false color content as well.  My image processing software is Adobe Elements, as opposed to photoshop or lightroom, so I'm not doing anything with channel swapping, but in the middle of the day, I got a couple of images outdoors, as well as a few flower images illuminated by window light.  These aren't specifically artistic to any degree, and the african violet is blurrier than I'd like due to a fan running nearby, but the motorcycle shot suggests that I'm getting reasonably good light transmission.  For the outdoor shot, it was probably f/11 or so aperture for roughly 2.5 seconds at ISO 1600.  The filter is the X-Nite BP1.  Everything in the image seems to show up nicely, and as expected, including the shaded areas under the bridge across the street.

[OlDoinyo]

Are you trying to shoot uv or ir? The second image is clearly mostly ir.

[dabateman]

The X-Nite BP1 is a 320nm to 670nm filter.

just like BG39.

that will give you a full spectrum look. If you are getting 2.5 seconds exposure with ISO1600, than something is seriously wrong with your camera.  

what other filter are you using? 

[CharlesS]

Camera was recently modified by MaxMax for UV only.  (I’ll have to look at the work order to see specifically what glass was used internally, but in theory, there ought to be no light contamination from IR.) I did try using the Xnite filter on my existing IR converted camera (a Nikon D7100) and got completely black test images, even on multisecond exposures.  I did do some tweaks in Elements, but nothing drastic.  
 

My experience with IR is that the paved area (the driveway) would be very dark, and not glowing pink/purple.  Hmmm…

[Andy Perrin]

Yeah, this is mostly IR in the bottom pic. Grass is never that bright in UV. UV images usually are between 1/30” and longer (typically 2 sec unless you are wide open and very high ISO). 

[nfoto]

I concur with Andy's analysis. This is IR and if any UV is present, the IR completely overwhelms it.

[CharlesS]

Thanks everyone - I just did a comparison test with the D7100 (IR) with and without the BP1 XNite filter using my tv remote control.  The remote was a very bright flash without the BP1, and a modest, but sill visible flashing with the BP1, in live view.    A quick google search suggests that typical remote control gizmos emit at about 910nm.

 

Using the Fuji S5, and the BP1 filter in place, the tv remote did register as a small flashing dot in live view, so IR is getting through the front filter over the lens, as well as through the internal filter over the sensor, (which I think is the XNite 330 glass.)

 

Will need to resolve...

[Andrea B.]

So, we have a Fujifilm S5 mod with an internal U330 filter and a Nikon 50/1.8 AI lens and a blue-green IR-blocker for the lens.

 

The only way  IR can get in there to the sensor is if there is one (or more) of the following happening:

 

1. light leak from open viewfinder, open port doors, etc. (I don't think so.)
2. the S5 has an internal IR shutter monitor. (I don't think so.)
3. internal filter is not U330 glass. (I don't think that is the case. MaxMax is reputable.)
4. the blue-green IR blocker BP1 is too thin.

 

1.) The photos do not look as though there is a light leak because light leaks typically produce an area of washed-out flare which is not uniform across the photo.

 

2.) Similarly, it does not seem like there is an internal IR shutter monitor causing problems because that typically also produces a non-uniform washed-out flare area.

 

3.) I'm sure it is U330 glass if MaxMax says so.

 

4.) You probably just need thicker IR blocking.

Remember that U330 glass is dual bandpass. It passes both UV and IR. So you need an IR-blocker of sufficient thickness to use with that U330.

• Not knowing exactly the thickness of the U330, I would probably first suggest the usual recommended 2mm thick blue-green S8612 IR-blocker.
• Given that you already have some kind of IR-blocker from MaxMax, it probably makes more sense monetarily to just add another inexpensive Chinese IR blocker to try to reach a 2mm IR-blocking thickness totally.
• As a 3rd suggestion, I would contact MaxMax and tell them they sold you a too-thin IR-blocker and could you please replace your BP1 with a thicker BP1. I don't know what MM is currently offering, so that might not be feasible and you'll have to go with one of the other 2 suggestions.

 

Hope this helps!

 

 

[Andy Perrin]

Yeah, I agree, it's the IR blocker falling down on the job. Look at the spectrum here, see how it passes all that IR? Your camera is still very sensitive in the 900nm range! And it's not even blocking the 700nm range very well. Even that tiny bump around 780nm is enough to wash out a UV image with sunshine as the light source. The X-NiteBP1 is not a suitable IR blocker for UV imaging. You need something stronger. I would just try to get a refund on the X-Nite and buy some S8612 2mm. 

 

Side note: Andrea, you can't just buy thicker BP1 - MaxMax doesn't sell different thicknesses. It might even be dichroic, not sure.

 

 

[CharlesS]

Thanks all!  Looking to order some thicker glass…