Hoya RM-90

[Cadmium]

I wanted to compare more closely some of the Schott and Hoya higher IR filters.

Specifically starting at 800nm,

Hoya IR-80 (IR-80N) - 800nm

Schott RG830 - 830nm

Schott RG850 - 850nm

Hoya RM-90 - 920nm

RG1000 - 1000nm

(Hoya filters names have "-" dashes, Schott filters names don't)

 

Here are comparisons, for 2mm thick, catalogue/reference thickness (Hoya = 2.5mm thick, Schott = 3mm thick), and 1mm thick.

 

All 2mm thick:

 

Reference thickness:

 

All 1mm thick:

[Cadmium]

Note the similar transmission profile between RM-90 2.5mm thick (stock/catalog/reference thickness) and Schott RG1000 1mm thick.

However, we don't know how they compare at OD5 exactly for sure, because the RG1000 3mm thick reference thickness bottoms out at OD5, and the program can only calculate from that data limit.

Other than that unknown, these two look the same to me.

 

[Andy Perrin]

Why is the data so jagged? It looks like it was sampled too coarsely.

[ulf]

Why is the data so jagged? It looks like it was sampled too coarsely.

It is because Hoya publish their transmittance data with low wavelength-resolution.

Often (always?), the resolution is 10nm steps below 750nm and 50nm steps above 750nm.

 

Schott have a resolution of 1nm in their data.

[Cadmium]

Yep, Hoya data sheets have some pretty big jumps, thus the reason the jagged graphs for the Hoya filters.

They make their data sheet graphs look a little bit more smooth, but take a look at the data:

http://www.hoyaoptics.com/pdf/RM90.pdf

[OlDoinyo]

Since all of these curves are a similar sort of sigmoid, could one spline such a curve to the data points and come up with something smoother?

[Cadmium]

The jagged Hoya curves don't bother me, and work fine for what I am doing here, which is simply to compare the slope and transmission range of RM-90 to similar Schott filters.

I don't need anything smoother to compare.

 

Off topic, but...

What would be more useful would be actual visual range data for the Hoya U filters which show no data in the visual range.

For example, the Hoya U-340 data sheet is completely absent of transmission data from 400nm to 660nm, and similar is true of the other Hoya U filter visual range data.

Maybe they don't think that data is important, but it actually is, especially when you are comparing Hoya and Schott U glass that is thinner than 1.5mm or 2mm.

There is a functional difference between the visual range of Hoya U-340 1-1.5mm and Schott UG11 1-1.5mm, but you can not show that from the Hoya data, because it doesn't exist or is unpublished.

 

http://www.hoyaoptics.com/pdf/U340.pdf

 

An example of this is compare these two stacks visually, with visual light only. NOT a UV light source.

UG11 1mm + S8612 2mm

U-340 1mm + S8612 2mm

You will see visible light with your eyes (starting around about 550nm and up) through the U-340 stack.

This is not true with U-340 that is thicker than about 1.5mm however, but this shows a difference between the U-340 and the UG11 in the visual range which is not demonstrated in any data or graphs.

This may also happen with UG11 if it is thinner, but at the same thickness UG11 blocks the visual range stronger than U-340.

 

(and you can use as much S8612 thickness in these stacks as you want, it will not suppress the visual light in the 500-600nm range)