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UltravioletPhotography

Comparison between BG3-stacks and BG25 stacks


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First take of the BG3- / BG25- filter stack comparison.

 

White balanced for a pleasing result.

 

The BUG3 filter-stack normally consists of S8612 and BG3, both 2mm, but there is an alternative blue filter that gives a similar, but not identical result, BG25.

This is a comparison to show the differences.

WB against PTFE often gives a weird tinted result. See Second take below.

 

Images to the left or first ( S8612, 2mm + BG3, 2mm ). Images to the right or last ( S8612, 2mm + BG25, 2mm ).

post-150-0-82706800-1625649806.jpg post-150-0-28562800-1625649316.jpg

The same unknown buttercup I used next day for focus stacking. https://www.ultravio...5-filter-stack/ In VIS it is yellow.

 

post-150-0-60163900-1625650662.jpg post-150-0-85860800-1625650671.jpg

Cherry blossoms collected late March 2020, from a tree just outside the house where live. In VIS they are pink.

 

Sometimes I prefer the results I get from the BG25-stack as it gives a wider range of green nuances and often are WB better to a pleasing result.

 

Second take of the BG3- / BG25- filter stack comparison.

 

White balanced against PTFE.

 

It i interesting to note that for the BG3-stack some parts of the yellow flower (red in the pictures), with specular reflection are white just like the WB-target.

The tinted result of the cherry blossoms is typical for most blue, pink and white flowers, while yellow flowers are less affected, compared to those in the first post.

 

Lessons learned here is that there is no correct WB for these types of filter-stack. These are false colours.

How to WB depend on what you are trying to enhance or show.

 

Images to the left or first ( S8612, 2mm + BG3, 2mm ). Images to the right or last ( S8612, 2mm + BG25, 2mm ). WB @ PTFE

post-150-0-06578600-1625811016.jpg post-150-0-26606700-1625811025.jpg

 

post-150-0-80876600-1625811062.jpg post-150-0-17761300-1625811047.jpg

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Thanks Ulf

You might want to check the filters mentioned again ?

These look good......but what do they look like with an in camera white balance or CWB please ?

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Thanks Ulf

You might want to check the filters mentioned again ?

These look good......but what do they look like with an in camera white balance or CWB please ?

 

Thanks Col, I found the error and corrected it =>BG25.

 

Sorry, I cannot help you with that.

I almost never do a in camera WB. It is normally rather meaningless for me as I switch between up to 20 different filters for the same motif/setup.

I keep the WB on the camera at a normal daylight setting.

I can partially identify the different filters, used for different images, by the colour of the thumbnail images, attached to the RAW-files.

 

The only exception to the rule of CWB, is when I shoot with my Sunex.

Then it is easier to compose images on the screen with correct WB.

 

For all other shooting I compose my images in VIS, with the first reference image, taken with a BG38 or BG40-filter on the lens.

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I will try and see if I can find image pairs of a yellow flower with a suitable UV signature too.

When that is done I will notify by a new post.

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I will try and see if I can find image pairs of a yellow flower with a suitable UV signature too.

When that is done I will notify by a new post. That was nonsense. The buttercup is a good example of a yellow flower.

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While this comparison is nice, it is a comparison of Ulf processing skills & getting a pleasing result to his taste.

Wouldn't a 'filter' comparison be better if it was in the correct light first, done in a standard way, then showing different processing ?

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Wouldn't a 'filter' comparison be better if it was in the correct light first, done in a standard way, then showing different processing ?

There is not a very significant difference in the spectral content of sunshine and from my perspex-protected flashes.

Also that light is very repeatable unlike sunshine. This is very much the correct light.

 

The result from these type of filer stacks WB against PTFE do not work well.

That causes a strong tint making comparison difficult or impossible. That is the reason WB with PTFE is normally not the way they are used.

There are images in the series with PTFE for all filters and I can show that too if it is of interest.

I really tried to get a WB that was as neutral as possible for both stacks without any aim for something artistic.

 

At least that is my understanding from communication with Cadmium.

Also I think the result is more sensitive to different sensor/camera types.

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While this comparison is nice, it is a comparison of Ulf processing skills & getting a pleasing result to his taste.

The images are just screen shots from FastRawViwer with exposure and contrast adjusted and a suitable one click WB to get a reasonable image.

The original images was a bit underexposed.

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Nice illustration of the differences between the BG3 and BG25 filters. Thank you.


 

I almost never do a in camera WB. It is normally rather meaningless for me as I switch between up to 20 different filters for the same motif/setup. I keep the WB on the camera at a normal daylight setting. I can partially identify the different filters, used for different images, by the colour of the thumbnail images, attached to the RAW-files.

 

I also use a large number of filters per subject. To avoid oversaturation and the subsequent obscuring of details which make it difficult to judge whether or not I've gotten a good exposure, I usually set the camera to monochrome and look at the resulting luminance/brightness histogram (not sure what it is named) to judge exposure.

 

Another good solution is to set your camera to a unitary white balance (if it is possible to do so). Then you are shooting in the "raw colors" with no white balance at all.


 

Another small comment: For some filters an interesting and easily obtained white balance may be made against Spectralon/PTFE. But for some filters, as Ulf has mentioned above, a white balance against Spectralon/PTFE produces a "strained" result. I recently referred to the "blue mess" I got by attempting a WB against Spectralon for a narrowband 340nm filter. See here -> https://www.ultravioletphotography.com/content/index.php/topic/4712-filter-test-34010-6-progress-was-made-finally-update-progress-was-then-lost/page__view__findpost__p__47311

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I have been considering copying or moving the Second take section up into the first post to make the viewing more convenient.

Maybe that is overdoing it. what do you think?

 

Once I thought it would be nice to also have an a bit more formal filter section similar to the Lens Data section to gather more technical filter topics in.

Is that a stupid Idea?

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You can either move the second set into the first set, or

you could add a link to the first set: See Post #10 for the second set.

Your call. :smile:

 

(FWIW, not every pair will display side-by-side in many browsers especially if on mobile. The best way to ensure side-by-side display is to put both photos on one canvas.)


Given that we have a filter section already, I would need to know what you mean by a "more technical filter topic".

 

 

.

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The current filter section is fine.

It must be my urge for having things well organised (except for my desk and workbenches. :-) )

 

The current Filter section is a discussion section and I was looking for something more organised, a bit like the formal botanical sections structure.

With a well defined topic name structure it will be easier to browse for information about specific filters and filter groups.

There might be different topic types divided by different naming or in subsections.

 

If you think this is stupid or just too ambitious we can just skip it.

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I was looking for something more organised.

 

How about this Sticky: Sticky :: UV/Vis/IR Filters

It lists manufacturers, links to transmission charts, has descriptions and discussions of the pros & cons of dichroic, stacked, coated filters.

It is pretty well organized.

 

There are *literally* hundreds of possible filters and there's no way anybody can organize them all.

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I have not tried with BG25, but my favorite stack using BG3 is bg3 1.5mm thick + S8612 1.5mm thick.

2mm + 2mm works, but you get a little more diverse colors out of the 1.5mm + 1.5mm thick stack.

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I have not tried with BG25, but my favorite stack using BG3 is bg3 1.5mm thick + S8612 1.5mm thick.

2mm + 2mm works, but you get a little more diverse colors out of the 1.5mm + 1.5mm thick stack.

That makes sense and I would expect almost identically more colours by a bg3 1.5mm thick + S8612 2mm stack.
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I was looking for something more organised.

 

How about this Sticky: <> Sticky :: UV/Vis/IR Filters <>

It lists manufacturers, links to transmission charts, has descriptions and discussions of the pros & cons of dichroic, stacked, coated filters.

It is pretty well organized.

 

There are *literally* hundreds of possible filters and there's no way anybody can organize them all.

That is perfect and precisely what I wanted.

 

I had forgotten this sticky as it is so static and never appears among "New content"

Maybe it can gradually be allowed to grow with suitable content?

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  • 1 month later...

Hmmm I got a BG3 by mistake ( ordered a ZB2 instead of a ZWB2, children dont buy stuff at midnight) and I didnt know what to do with it.

 

Ulf thankyou for giving me ideas!

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