MidOpt DB850 filter

[Cadmium]

Here are some pics of the MidOpt DB850 filter.

It is basically a dichroic filter that sharply removes the 700nm to 800nm range.

Ask Andy about his use of this filter, stacked with #12, then processed for EIR simulation.

I am posting this for Colin, and others.

Point being here that you can order different thicknesses, sizes, mountings, and non mountings (just the glass, as I did here, and custom mount yourself).

Here I ordered 49mm dia (to fit my usual 52mm ring), and 2mm thick glass. They sell multiple thicknesses, ask Colin about that.

I made an identical copy for Andy also.

Since this filter is just clear glass with dichroic coatings, the thickness will not mater for the transmission.

The filter does have some color shift at an angle (typical of dichroic coated filters), so assume some color shift from center to sides with wider angle lenses.

 

 

 

[dabateman]

Interesting that you ordered a 2mm one. I would have expected you to get a 1mm one, then glue in a #12 gel and add 1mm glass on top to hold it all together.

I guess you could just stack it with a #12 Schott equivalent filter.

 

[Cadmium]

That would cut down on the versatility of the filter...

[colinbm]

Thanks Steve

I ordered one from the Australian agent & they told me it is only available in a 52mm ring at 0.75mm thick......I think they are hoping I'll break it ?

i will know in a month if it survives the trans Pacific flight & the trauma of going through Australia Post....kangaroos would be gentler......:-(

[Cadmium]

Thanks Steve

I ordered one from the Australian agent & they told me it is only available in a 52mm ring at 0.75mm thick......I think they are hoping I'll break it ?

i will know in a month if it survives the trans Pacific flight & the trauma of going through Australia Post....kangaroos would be gentler......:-(

 

Colin, You're Welcome. Maybe they only make one thickness available for the rings they use, but they have multiple thickness available for the unmounted glass.

This filter glass comes in 0.8mm, 1mm, and 2mm thicknesses.

Oh, I didn't know you had already purchased it yet. I am sure it will work fine with the 0.75/0.8 thickness.

 

Interesting that you ordered a 2mm one. I would have expected you to get a 1mm one, then glue in a #12 gel and add 1mm glass on top to hold it all together.

I guess you could just stack it with a #12 Schott equivalent filter.

 

Use a Tiffen #12 or some other glass filter equivalent in the low 500nm range. RG515, RG530, RG550 for example.

Ask Andi.

[Andy Perrin]

Huh, that is an peculiar size!

 

Definitely I found that cutting out the 700-800nm range in combination with the Tiffen#12, with proper processing, would allow me to do IRG images with a single photo. Even without processing, however, the colors seemed more intense to me.

[OlDoinyo]

I will be curious to see a demonstration of how much real-world difference it turns out to make, vs. merely using the #12 by itself. The dichroic nature does make it potentially problematic for FOV>30^o.

[Andy Perrin]

OlDoinyo when I get a chance. I don’t know why you would doubt it though since you know what a difference there is between 720nm long pass and 850nm longpass.

[OlDoinyo]

I am not saying I do not understand the principle--the IR captured by the camera's blue channel results in an image whose profile will be somewhat different than that captured as a part of the red-channel image, so the subtraction is technically inequivalent. But the light in this band is only a part of what goes into an IRG image, and artistically speaking, we do not know how how significant a part it plays--until we run an actual test. I am not assuming I know the answer.

[Andy Perrin]

Ok, it’s just going to take a while since the test is going to have to involve an actual IRG, a version with just Tiffen, and one with Tiffen+DB850.

[eye4invisible]

Too bad their Canadian distributor doesn't carry anything larger that 27mm.

[Cadmium]

Huh, that is an peculiar size!

 

Definitely I found that cutting out the 700-800nm range in combination with the Tiffen#12, with proper processing, would allow me to do IRG images with a single photo. Even without processing, however, the colors seemed more intense to me.

 

What is a peculiar size?

 

I am not saying I do not understand the principle--the IR captured by the camera's blue channel results in an image whose profile will be somewhat different than that captured as a part of the red-channel image, so the subtraction is technically inequivalent. But the light in this band is only a part of what goes into an IRG image, and artistically speaking, we do not know how how significant a part it plays--until we run an actual test. I am not assuming I know the answer.

 

Clark, I have not used or tested the DB850 stack much yet, but if I understand Andy's idea at all correctly, the idea is that the 700-800nm range being more heavily weighted with red via the Bayer transmission,

unevenly pollutes the processed results. Removing the 700-800nm delivers a cleaner IR to the process equation.

Does that sound right, Andy? I could be way off...

 

Too bad their Canadian distributor doesn't carry anything larger that 27mm.

 

Andy, You can order whatever you want, like I noted above. If your local place will not do that, it is not because they can't. You can always order it from the distributor that Andy and I got ours, in Massachusetts,

but ANY MidOpt distributor location has access to ordering anything you want. I did find this distributor VERY helpful and fast:

RMA Electronics, Inc.

35 Pond Park Road

Suite 12

Hingham, MA 02043

781-749-9700

[Andy Perrin]

Andy Perrin, on 18 February 2020 - 10:51, said:

 

Huh, that is an peculiar size!

 

Definitely I found that cutting out the 700-800nm range in combination with the Tiffen#12, with proper processing, would allow me to do IRG images with a single photo. Even without processing, however, the colors seemed more intense to me.

 

What is a peculiar size?

0.75mm!

 

I did find this distributor VERY helpful and fast:

RMA Electronics, Inc.

35 Pond Park Road

Suite 12

Hingham, MA 02043

 

781-749-9700

Seconding that -- they were incredibly nice to me also.

[Cadmium]

Well, not exactly 0.75mm as Colin said above, the thicknesses that were quoted to me for this particular filter for the unmounted glass only version were: 0.8mm, 1mm, and 2mm.

Not a lot of difference between 0.75mm and 0.8mm both are very thin. Even 1mm is rather thin.

They make pre-lapped crown glass in many various thinner than 1mm thicknesses, such as even 0.5mm thick, etc., and they may even be using crown glass for the substrate.