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[Filter Test SEU Gen2 #7] Measured Filter Transmission


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[Filter Test SEU Gen2 #1] Introduction to the SEU Gen2

[Filter Test SEU Gen2 #2] White Balance, Raw Histogram & Andrea's "White Signature"

[Filter Test SEU Gen2 #3] Filter Speed & A Windy Bull's-eye

[Filter Test SEU Gen2 #4] Dealing with the Usual Dichroic Effects

[Filter Test SEU Gen2 #5] Landscape Interlude

[Filter Test SEU Gen2 #6] Monochrome Museum Comparison

[Filter Test SEU Gen2 #7] Measured Filter Transmission

[Filter Test SEU Gen2 #8] Dichroic Reflection Detour

[Filter Test SEU Gen2 #9A] Longpass Stack Wandering Discussion. See #9B for results.

[Filter Test SEU Gen2 #9B] Longpass Stack Results

[Filter Test SEU Gen2 #10] What good is a filter test without a Rudbeckia?

[Filter Test SEU Gen2 #11] A Fascinating New Rudbeckian View

[Filter Test SEU Gen2 #12] Summary


 

Measuring the SEU Gen2

 

I have just completed a big measuring session of the SEU Gen2

The resulting spectrogram is a composite of several different measurement parts, optimal for each different wavelength section.

Some of the spectral sections are the result of averages from very many measurements, to reach the dynamic needed.

 

The filter looks very promising with a favourable Sraight Edge response.

As most members already know the dominant peak is in a region where both the UV-sensitivity of the sensor is highest and where the sunlight contain most UV.

The filter seams to have the edge transition slightly further towards the blue compared to the SEU Gen1.

Transmission Linear:

post-150-0-25623900-1532113828.png

 

Transmission Logarithmic:

post-150-0-71997800-1532113850.png

 

The lower limit of this diagram equals an attenuation of OD5.

I do not expect that the narrow peak (6nm) at 524nm OD3.6 will cause any problem at all.

It will be interesting if any faint trace of this tiny level could be seen under practical use of the filter.

 

----

If there is an interest in the methods I used, I can write abut how the full measurement was done, in detail, in another topic.

Please let me know.

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Thank you for the spectra. In an other thread I see Jonathan also has this filter. If he tested it with his gg455 and gg495, then we may get an idea of how much leakage these bands really let in.
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As always, it is IR leakage which is the destroyer of UV. So as long as everything is OD 3.6 or better, which is the case here, I would not expect to see any "contamination".

 

We will however follow the data and the photo experiments where they lead us. :D

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As always, it is IR leakage which is the destroyer of UV.

That is what we are used to see.

 

This is because all ionic UV-filter glass-materials used has their secondary peak in the IR-range.

However the sun spectrum is ca 20% stronger at 524nm than at 700nm!

 

So as long as everything is OD 3.6 or better, which is the case here, I would not expect to see any "contamination".

I normally prefer >OD4 as I see slight traces of IR in my BaaderU images.

I measured my BaaderU to have an IR peak of OD4.0 at 731nm.

 

Those traces are not present with my U-360-stack, that my measurements confirm has a >OD5, just as the Schott calculator predict.

 

I still think and hope that the SEU2 would see less or no problems because:

1. I think the reflectivity in UV-signature areas often can be lower at 524nm than in IR.

2. The sensor sensitivity is higher at the SEU2 peak transmission.

3. The solar spectrum is more intense at the SEU2 peak than our traditional UV-pass filters

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Excellent points, Ulf.

 

3. The solar spectrum is more intense at the SEU2 peak than our traditional UV-pass filters

I would add to #3 that the top of the SEU2 curve is not singly "pointed". There is a nice range of peak transmission. Excuse me, I do not know how to word what I'm trying to say.

 

 

*****

 

 

I wonder sometimes if we can record different spectra when shooting landscapes as opposed to shooting close-up with the same filter? I ask this because -- as an informal observation -- I often get greenish or green-yellow tones in a landscape which I do not seem to find in the flower close-ups. Repeat, that is a very informal observation. I have not run any controlled experiments. I will note that my floral close-ups often involve the added UV-flash which certainly could alter the recorded UV spectrum. But I also have quite a lot of floral close-ups made under sunlight only.

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Andy Perrin
3. The solar spectrum is more intense at the SEU2 peak than our traditional UV-pass filters

I would add to #3 that the top of the SEU2 curve is not singly "pointed". There is a nice range of peak transmission. Excuse me, I do not know how to word what I'm trying to say. <laughing>

I think I know what you mean, although Jonathan shows in his corrected graph that the actual absorption by the sensor is rather pointed:

http://www.ultravioletphotography.com/content/index.php/topic/2880-filter-test-seu-gen2-6-monochrome-museum-comparison/page__view__findpost__p__22664

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