What filtration for UV flash modification?

[Doug A]

Living less than 500 foot above sea level, I'm convinced electronic flash is needed. Last year I bought some Pentax AF540 FGZ shoe mount flashes. One was thrown in because it was missing the pull out white bounce card and flip down wide-angle diffusion panel. Now, with my help, it's missing the front Fresnel lens. 

 

I've had different recommendations for filtering. One said put 6mm of Chinese ZWB-1 on the flash. Another is using Hoya U340 and Midopt BP 365 camera filters. As a quick experiment, I borrowed the ZWB-1 filters out of the two Nemo torches. This gives me 4mm on the flash.

 

With the Pentax K1 Full Spectrum, original metal body Nikon EL-Nikkor 135mm (standard ZWB-1/BG39 filter stack) on Pentax bellows, the pictures don't look bad. I'm using the same custom white balance set for Ioriginal 35mm lens. Flash looks fairly similar to daylight. Same setup on Ioriginal 35 lens has a little bit of a yellowish tint. 

 

So what filters are recommended for a UV flash?

Thanks,

Doug A

 

 

 

[nfoto]

You probably need to get the IR output down as not to overwhelm your UV bandpass filters. Anything that curtails IR and lets UV through would be OK.

 

I don't use filters on my Broncolor studio flashes (uncoated xenon tube) as the Baader U is dealing nicely with their IR contribution. In the field I use on occasion the Nikon SB-140 flash(es) and it has a filter attachment similar to Wratten 18(type 18b if I recall correctly).  The NEMO torches should work out of the box if your over-the-lens filter is good enough.

[Cadmium]

U-340 2mm + S8612 2mm

[Doug A]

Thank you @nfoto. I'm getting better results with plants using flash. So I will work on improving the set up.

 

Want to upgrade my lens filtration, just haven't figured out which way to go. Baader isn't recommended for wide angle lenses and is a little finicky to reverse and fit to standard lens filter threads. It rewards the user with great contrast.

 

Thanks for the help,

Doug A

[Doug A]

@Cadmium I looked at your site for a 52mm S8612 to replace the BG39, but it was out of stock. Is this a temporary thing, or tied to world events?

 

Thanks,

Doug A

[dabateman]

Currently I just have a 1mm window of PMMA wrapped in a layer of plumbing tape (PTFE) on my flash head.

I also have slide over covers with 2mm Zwb2, that I made. But I rarely use them. I judt filter on lens and use flash almost naked.  Well with PMMA for protection incase the bulb explodes. 

[JCDowdy]

Since you asked about filtering a flash and not a lens I would say Chinese 2mm ZWB-1 stacked with 2mm QB39 and have them cut to fit the front Fresnel lens frame.

If also using a comparable stack on the lens for reflected UV you may only need a ZWB on the flash.

For UVIVF you need both on the flash plus a UV/IR blocker of some type on the lens.

[Guest]

1 hour ago, JCDowdy said:

Since you asked about filtering a flash and not a lens I would say Chinese 2mm ZWB-1 stacked with 2mm QB39 and have them cut to fit the front Fresnel lens frame.

If also using a comparable stack on the lens for reflected UV you may only need a ZWB on the flash.

For UVIVF you need both on the flash plus a UV/IR blocker of some type on the lens.

 

UVIVF with a flash, really? I mean really!

 

So, what type of exposure are we looking at compared to a standard 365nm torch? I usually go around 4-8 seconds at ISO 100. Can a 200 Watt flash do as good at 1/160 for UVIVF? Are we talking about multiple fires per frame?

 

Also, my Chinese made 365nm UV torch only has one glass piece not two. What is that usually, a combination of ZWB-1 and QB39 together?

[Guest]

This is the glass from a UV Beast V3 365nm Chinese made torch. It is sandwiched in between two pieces of cardboard and the front flashlight holder. All the light from the strobe is blocked only passing through the UV glass. The first first of cardboard is cut smaller than the glass. The glass is inserted snugly into the second piece. It it held on front by the flashlight part.

 

The filter is taped onto a 200 Watt filament bulb that is partially coated backed with a reflector. I guess a completely uncoated bulb would allow more UV to pass through the system. I could try it on the speedlite head at 200 Watts.

 

 

 

The setup was with the glass 8cm from the subject set at full power of 200 Watts. The lens is a Kuriybayashi 35mm f3.5 with a Hoya UV(0) on front.  The camera is a Sony a6300 unmodified. All photos were taken in a completely dark room. White balance was set to 9900K in post.

 

 

ISO 100 f/8 1/60s - Round Head 200 Watts

 

 

ISO 400 f/8 1/60s - Round Head 200 Watts

 

 

ISO 800 f/8 1/60s - Round Head 200 Watts

 

 

ISO 1600 f/8 1/60s - Round Head 200 Watts

 

 

ISO 100 f/3.5 1/60s - Round Head 200 Watts

 

 

ISO 400 f3.5 1/60s - Round Head 200 Watts

 

 

ISO 800 f/3.5 1/60s - Round Head 200 Watts

 

 

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Additional photos taken using only a smaller yet powerful 3 LED Torch 365nm Lumen Shooter S3 8CM from subject. No strobe was used for the photos below, only a flashlight.

 

ISO 100 f3.5 1/60s - UV Torch 365nm

 

 

ISO 800 f3.5 1/60s  - UV Torch 365nm

 

ISO 1600 f3.5 1/60s  - UV Torch 365nm

 

ISO 100 f3.5 1.5s  - UV Torch 365nm

 

 

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More testing with a different head. This is the speedlite attachment. It had some light leak so I wrapped it up real good all around.

Same setting full power and 8cm distance. This filament bulb does not appear to have any type of coating when photographed under reflected UV. 

 

 

 

 

For the same settings as the other round head there is more light exposing the subject. Maybe even twice as much. I did not need to go to ISO 800 with f/3.5, just ISO 100, 200 and 400. With f/8 ISO 100, 400 and 800. I think I am going to use this setup for UVIVF and see how it works with stacking. I also want to try two fires of the strobe per frame with micro. This should be possible using the wireless remote, but I will have to set the camera exposure long enough for fire, recycle and fire in a completely dark room. My other option is to get a second flash like this or larger glass cut for the window. Overall I am happy with the results. 

 

 

ISO 100 f/3.5 1/60s - Speedlite Head 200 Watts

 

 

ISO 200 f/3.5 1/60s - Speedlite Head 200 Watts

 

 

ISO 400 f/3.5 1/60s - Speedlite Head 200 Watts

 

 

ISO 100 f/8 1/60s - Speedlite Head 200 Watts

 

 

ISO 400 f/8 1/60s - Speedlite Head 200 Watts

 

 

ISO 800 f/8 1/60s - Speedlite Head 200 Watts

 

 

 

 

 

 

[colinbm]

8mm ZWB1 on the flash outputs UVA.

[Doug A]

@Blazer0ne that's a lot of experimenting. Your are ahead of me and your results show it. Most UVIVF seems to be with flash - multiple flash units. Some do build exposure by multi popping. I've just started experimenting so it is a little difficult to give exact settings. Nothing I've shot in UV has ever turned out at ISO 100. ISO 1000 is probably unlikely. I've only tried 1 Nemo torch ( own 2) and 1 modified flash. Nemo only has 1 filter. Took 2 apart and stacked them for my flash experiment. 

 

I will try to post a UVIVF photo when finished processing it. I'm having a tough time deciding how to process something I've never seen. 

 

[colinbm]

Photo Ninja is UVA friendly for processing.

[Guest]

Thanks! It only took a few minutes to slap that torch filter over my strobe and cut out the cardboard. I never really considered filtering the flash until it was mentioned here. I just didn't think the output and exposure would match up, but they are pretty good. I think. That was the point of this test. To see what exposure and power was required.

 

All my reflected UV photos have been ISO 100 with two strobes set at either 1/1 or 1/2 using a 200W light coat and 360W uncoated. I have no filter on the flash heads. I only use a Baader U-Venus filter over the lens.

 

I don't know why anyone would want a filter over the flash for reflected UV. Do you put a big hundred million mile wide filter over the sun when you are outdoors taking reflected UV? UVIVF is different because you are exciting the subject with UV light and a full spectrum would wash it out when shitting in visual IR/UV cut over the lens. That is the only reason I see to have a filter over the flash for UVIVF or UVIIF. I am no expert here. I just have all this stuff laying around and when it lines up I get results. 

[colinbm]

The Sun puts out at sea level only weak UVA, the flash puts out stronger into UVC.
UVIVF requires a reasonably pure UVA & the camera wants to only see a reasonably pure visible light.

[Guest]

Would the bayer cfa or coverglass help in that case?

[colinbm]

An unmodified normal digital camera is OK for UVIVF, but an extra UVA cut filter like the Zeiss T* UV Filter is recommended.

[Doug A]

For reflected UV I tried unfiltered flash with the Ioriginal 35mm lens and his filter pack of ZWB-1(2mm)/BG39(2.3mm). The flash overpowered the filters. So I cannibalized the Nemo flashlights to add their filters to the flash. The colors are much closer to what is expected in reflected UV photography.

 

Need a filter upgrade. Then the flash filter can be removed. Just not sure what to get yet.  Baader looks great, but there are warnings about using it on wide angle lenses. My only UV lens, at the moment, is a 35mm wide angle on a full frame camera.

 

I'm using a stock Pentax 645Z with Pentax 120 macro lens and Tiffen haze 2 UV filter for UVIVF. Getting decent results with single Nemo torch or modified for UV Pentax flash.

 

Thanks,

Doug A

[nfoto]

The Baader U is indeed bound to create some colour unevenness across the frame when added in front to a 35mm lens on an FX/full frame camera. However, if you can achieve rear filtration, it behaves much better using the same lens + camera. This is my usual setup for the Baader U for lenses 35mm or wider.

[Guest]

 

Ordered these for the 200 watt speedlite head to do UVIVF with my unmodified a6300. 

 

[JCDowdy]

18 hours ago, Blazer0ne said:

UVIVF with a flash, really? I mean really!

As you so quickly demonstrated, like a duck to water!

[Andrea B.]

Flash-induced fluorescence works better with some subjects than with others, as everyone will no doubt discover. As an example, flash picks up fluorescent pollen nicely, but isn't always so useful for other those subjects which have a more "gentle" fluorescence.

 

I think you will pretty much find out that you want the "proper" double filtration when using flash to induce fluorescence. As Doug mentioned above, it's very easy for flash to overwhelm the both scene and the lens.

 

Don't forget the easy-to-perform Shiny Metal Test !! You can scroll down in this topic:

 

 

 

 

[Guest]

2 hours ago, JCDowdy said:

As you so quickly demonstrated, like a duck to water!

I admit it was probably short sighted to order those cut glass filters. For example it isn’t clear to me how a filter can get overpowered. It’s not always easy finding the right information here. Everyone seems to have their own opinion. The site admin gets to watch us squirm. I’ll run the spoon test and see what it shows for my torch filter fitted to the flash. Honestly the only real money I have put into UV was the Baader U-Filter and I didn’t even get that advice from this site. It’s just nice to share what I have. 

[Pufferchung]

19 hours ago, Blazer0ne said:

This is the glass from a UV Beast V3 365nm Chinese made torch. It is sandwiched in between two pieces of cardboard and the front flashlight holder. All the light from the strobe is blocked only passing through the UV glass. The first first of cardboard is cut smaller than the glass. The glass is inserted snugly into the second piece. It it held on front by the flashlight part.

 

The filter is taped onto a 200 Watt filament bulb that is partially coated backed with a reflector. I guess a completely uncoated bulb would allow more UV to pass through the system. I could try it on the speedlite head at 200 Watts.

 

 

 

The setup was with the glass 8cm from the subject set at full power of 200 Watts. The lens is a Kuriybayashi 35mm f3.5 with a Hoya UV(0) on front.  The camera is a Sony a6300 unmodified. All photos were taken in a completely dark room. White balance was set to 9900K in post.

 

 

ISO 100 f/8 1/60s - Round Head 200 Watts

 

 

ISO 400 f/8 1/60s - Round Head 200 Watts

 

 

ISO 800 f/8 1/60s - Round Head 200 Watts

 

 

ISO 1600 f/8 1/60s - Round Head 200 Watts

 

 

ISO 100 f/3.5 1/60s - Round Head 200 Watts

 

 

ISO 400 f3.5 1/60s - Round Head 200 Watts

 

 

ISO 800 f/3.5 1/60s - Round Head 200 Watts

 

 

--------------------

--------------------

 

Additional photos taken using only a smaller yet powerful 3 LED Torch 365nm Lumen Shooter S3 8CM from subject. No strobe was used for the photos below, only a flashlight.

 

ISO 100 f3.5 1/60s - UV Torch 365nm

 

 

ISO 800 f3.5 1/60s  - UV Torch 365nm

 

ISO 1600 f3.5 1/60s  - UV Torch 365nm

 

ISO 100 f3.5 1.5s  - UV Torch 365nm

 

 

---------------------

---------------------

 

More testing with a different head. This is the speedlite attachment. It had some light leak so I wrapped it up real good all around.

Same setting full power and 8cm distance. This filament bulb does not appear to have any type of coating when photographed under reflected UV. 

 

 

 

 

For the same settings as the other round head there is more light exposing the subject. Maybe even twice as much. I did not need to go to ISO 800 with f/3.5, just ISO 100, 200 and 400. With f/8 ISO 100, 400 and 800. I think I am going to use this setup for UVIVF and see how it works with stacking. I also want to try two fires of the strobe per frame with micro. This should be possible using the wireless remote, but I will have to set the camera exposure long enough for fire, recycle and fire in a completely dark room. My other option is to get a second flash like this or larger glass cut for the window. Overall I am happy with the results. 

 

 

ISO 100 f/3.5 1/60s - Speedlite Head 200 Watts

 

 

ISO 200 f/3.5 1/60s - Speedlite Head 200 Watts

 

 

ISO 400 f/3.5 1/60s - Speedlite Head 200 Watts

 

 

ISO 100 f/8 1/60s - Speedlite Head 200 Watts

 

 

ISO 400 f/8 1/60s - Speedlite Head 200 Watts

 

 

ISO 800 f/8 1/60s - Speedlite Head 200 Watts

 

 

 

 

 

 

I am not an expert but I think you probably need to use an aluminum black foil tape (duct tape made for sealing hot/cold air duct tape) to block IR leak from cardboard :-) 

[dabateman]

BlazerOne, 

I think you should have ordered the BG39 equivalent not the bg38 equivalent.  Bg38/qb21 might let in too much IR.

[Doug A]

4 hours ago, Blazer0ne said:

For example it isn’t clear to me how a filter can get overpowered. It’s not always easy finding the right information here. Everyone seems to have their own opinion. 

A filter can only attenuate so much. It is probably simplistic and wrong, but I like to think of a filter as a sponge for light. Once the sponge is full, it leaks. Everything has a limit. 

 

There are different opinions here. Probably because people have different equipment and goals.  Some lean artistic, others scientific. I've never belonged to a forum with such a high ratio of scientists. Everyone has been so supportive and helpful. UV/IR is a vast field and it is going to take time too learn the basics. I'm enjoying the ride.

 

Looking forward to seeing your new filters in action. 

 

Thanks,

Doug A