Discussion of Collodion Emulation

[dabateman]

Ok I understand now, you actually know what to look for because you actually make the colloidal mix. Thats the problem I have with Aerochrome, I never shot it so don't know what it looks like. I just go for the look I like at the moment.

 

So you actually can compare Bg25 and Zwb3. Interesting.

 

As I posted here I think the Chinese QB5 might be closest to the spectrum people mention:

https://www.ultravioletphotography.com/content/index.php/topic/3613-uv-landscapes-sierra-nevada-california-october-2019/page__view__findpost__p__43514

[Cadmium]

Cadmium you did a magic ... putting composite curves. your second graph (BG25 + BG39) is much clearer than mine which I created with photoshop.

I hope the BG39 - ø52mm that I ordered from AliExpress from Tangsinuo Store arrives soon ... she write April 16!

Today I tried all the old filters I had at home with the standard Nikon Z5 and the Sony A7 full spectrum ... with flash light and that of the tanning lamp. below I put the result.

Today I have prepared some collodion with Rhen formula with lithium (sometimes I use the New Guy recipe with Cadmium :-)))

Tomorrow I try to do a practical test, but I doubt that the comparison with Sony A7 is useful.

Thank you

Toni

 

Photoni, Thank you. :-) I don't have any experience with Collodion Emulation myself, and I don't know what the transmission is, I just used the standard and most usual thicknesses in my graphs.

I am not sure what thicknesses Ulf has in mind.

I have UG2A here in 0.7mm, 1mm, and 2mm versions, and UG5 and/or U-330 available here in 1mm, 1.5mm, and 2mm thick versions.

2mm is the basic thickness of most filters, a starting point, kind of, so that is why I used 2mm in my graphs.

I can make the plots in whatever thicknesses you can think of.

 

And, very nice photo examples too!

[photoni]

Toni, you can make such graphs yourself with Schott's calculation tool if you have access to Excel.

The tool is found here in the "Miscellaneous" section:

https://www.schott.c...glass/downloads

 

thanks ... but I have never used excel :)

[photoni]

Ok I understand now, you actually know what to look for because you actually make the colloidal mix. Thats the problem I have with Aerochrome, I never shot it so don't know what it looks like. I just go for the look I like at the moment.

 

So you actually can compare Bg25 and Zwb3. Interesting.

 

As I posted here I think the Chinese QB5 might be closest to the spectrum people mention:

https://www.ultravio...dpost__p__43514

 

probably the QB5 is too tight ... but it should be practical for emulation.

the QB3 is wider but sees a lot of IR. it is similar to my BG25, it needs the BG39 I ordered.

Thanks

[photoni]

Photoni, Thank you. :-) I don't have any experience with Collodion Emulation myself, and I don't know what the transmission is, I just used the standard and most usual thicknesses in my graphs.

I am not sure what thicknesses Ulf has in mind.

I have UG2A here in 0.7mm, 1mm, and 2mm versions, and UG5 and/or U-330 available here in 1mm, 1.5mm, and 2mm thick versions.

2mm is the basic thickness of most filters, a starting point, kind of, so that is why I used 2mm in my graphs.

I can make the plots in whatever thicknesses you can think of.

 

And, very nice photo examples too!

 

cadmium, I'm probably looking for a solution to an impossible emulation.

it's very nice to complicate life :)

thanks

[photoni]

per semplicità inserisco le immagini di questo sito

 

 

https: //www.lundphot...odion_film.html

 

 

e di questo sito

 

https://www.dpreview.com/forums/thread/4535813

[JMC]

In the book "The Theory of the Photographic process, 4th Ed" by TH James, 1977, there is a section on measurement of spectral sensitivity of black and white materials.

 

There is one figure which shows wedge spectrograms of unsensitized, orthochromatic and panchromatic materials (using a similar device to what Lund showed). The unsensitized material starts its sensitivity curve at about 380nm and then loses sensitivity by about 495nm, however the author did comment that that lack of sensitivity shown in the blue and UV region was likely due to the use of a Tungsten light source.

 

Now, I'm guessing that 'unsensitized' material is similar to how a collodion plate would behave. So as mentioned above, while at first glance something like BG25 is a close match to the sensitivity curve that Lund shared, the fact that digital sensors drop in sensitivity in the UV region, it may be closer to reality to try something like UG5 in 2mm. However as I said above, whether there would be a huge difference int he final picture between using UG5 2mm and BG25 2mm would need to be tested, and if you are trying to focus with the filters on you'll see a lot more with the BG25 filter than the UG5 one.

[photoni]

Ho assemblato le due grafiche, sembra impossibile fare un'emulazione.

forse il più semplice ma "estremo" è il filtro "UV Kolari Vision" o il cinese QB5

[photoni]

In the book "The Theory of the Photographic process, 4th Ed" by TH James, 1977, there is a section on measurement of spectral sensitivity of black and white materials.

 

There is one figure which shows wedge spectrograms of unsensitized, orthochromatic and panchromatic materials (using a similar device to what Lund showed). The unsensitized material starts its sensitivity curve at about 380nm and then loses sensitivity by about 495nm, however the author did comment that that lack of sensitivity shown in the blue and UV region was likely due to the use of a Tungsten light source.

 

Now, I'm guessing that 'unsensitized' material is similar to how a collodion plate would behave. So as mentioned above, while at first glance something like BG25 is a close match to the sensitivity curve that Lund shared, the fact that digital sensors drop in sensitivity in the UV region, it may be closer to reality to try something like UG5 in 2mm. However as I said above, whether there would be a huge difference int he final picture between using UG5 2mm and BG25 2mm would need to be tested, and if you are trying to focus with the filters on you'll see a lot more with the BG25 filter than the UG5 one.

 

This afternoon I hope the wet collodion solution, the silver nitrate, the develop ....... and my son are good

[dabateman]

Ho assemblato le due grafiche, sembra impossibile fare un'emulazione.

forse il più semplice ma "estremo" è il filtro "UV Kolari Vision" o il cinese QB5

 

Yes the advantage of the QB5 is it wouldn't have the IR leakage. But only you will know if any of these filters look like the real plate.

For the rest of us there is just too much blue.

 

A work around Warren did was extract and only use the blue channel from a full spectrum converted camera. But that will not eliminate IR leakage, you would need to subtract out either the green or red channels to be IR free.

[JMC]

Some more interesting background "The wet collodion process - A scientific approach" - https://www.imaging.org/site/PDFS/Papers/1997/IST-0-4/159.pdf

[Stefano]

If I have time later I could try manually sampling Ulf's curves (sensor sensitivity) and adding them in the Schott filter calculator. Then you can more easily take the sensor sensitivity into account.

[ulf]

If I have time later I could try manually sampling Ulf's curves (sensor sensitivity) and adding them in the Schott filter calculator. Then you can more easily take the sensor sensitivity into account.

That is a good idea, Stefano.

I think the Schott filter calculator interpolates between omitted points so the sensitivity data do not have to have many points to be meaningful as the sensitivity varies rather smoothly.

What we are looking for is just the general sensitivity trend in the interesting wavelength range.

[photoni]

 

Today the collodion had a tantrum, after 3 test shots with fruit

Collodion with lithium formula, Petzval 200mm f3.5 3000 + 3000W flash elinchrome lens without UV treatment

probably the silver bath in damage

... it's all wrong, I stopped.

 

I repeated the tests with the standard Z5, and A7 full spectrum, with schott BG25 filter to verify this set, ISO 50, f: 16, 350 + 350w

it's a SURPRISE ... a CONTRADICTION, the BG25 works on the Z5, the dandelion is dark,

crazy !!!

[dabateman]

I am surprised by the Z5 result. The spectrum here for a stock z5 would indicate its not very UV sensitive:

https://www.primalucelab.com/world/nikon-z5-full-spectrum-for-astronomy-uv-and-ir-photography.html

 

Maybe dandelions dark core extends into 435nm or so. I will have to test that with my 405bp10 and 450bp20 filters.

[photoni]

I redid the test with full spectrum A7 with and without BG25

I also tried the Nikon Z5 and Z7 and D810

they behave the same way.

To the dandelion I added a narcissus, a small yellow flower and behind a white daisy from my lawn

.

 

Sorry I have no other filters that cut the visible.

thank you

Toni

[colinbm]

These are looking great Toni

[Stefano]

I sampled the blue curve in Ulf's image every 50 nm, it is very rough and spiky but since I don't know the real sensitivity of Toni's sensor it doesn't make sense to be precise. It's indicative only.

 

I tried sensor + S8612 (2 mm) + UG5 (2 mm) and got this (black curve, normalized):

 

Lacks some sensitivity to the right, but not bad.

[Stefano]

How about this:

Sensor + BG3 (1.5 mm) + S8612 (2 mm), black curce, normalized.

 

But the sensor curve looks odd, let me check...

 

Yes, sorry, I added an extra zero in a few places, fixed. This is as before, but the correct version:

 

Still not bad.

[colinbm]

Toni, what are the 60w, 3000w etc figures please ?

[photoni]

Toni, what are the 60w, 3000w etc figures please ?

 

the reference is to flash power. I have 4000W, 3000W and 1000W maximum power generators, which I can lower up to 60W

There are many types of tubes that produce flash light, the older ones are clear quartz, they produce very cold light from 5500 ° K to 6000 ° K and also produce UV (the ones I use).

today almost everyone has a light layer of yellow to remove UV and bring the temperature to 5000 ° K or less, only Prophoto I think produces two types, transparent and anti UV.

Birna Rørslett ... nfoto ... I read that she uses Broncolor flash, I don't know the specifics.

[colinbm]

Thanks Toni, yes that is a lot of light.

Your photos are sharp & very clear, are they photo stacked ?

I have a Godox 200A that has, I hope, clear tubes.

I am needing to know how to connect via its cable to my Sigma fp full frame mirrorless camera, now full spectrum, & use it.

[JMC]

Just did a quick experiment in the garden. Three filter setups, i) Schott S8612 1.5mm with Baader UV/IR cut (similar to internal filtration on normal unmodified camera), ii) Schott S8612 1.5mm plus BG25 3mm, iii) Schott S8612 1.5mm plus 1.5mm ZWB3.

 

Photos taken on a multispectrally modified Canon EOS 5DSR, with a 40mm f.28 pancake lens. Settings f8, and ISO800 for all. Images saved as JPEG in camera, and then desaturated and auto contrasted in Photoshop before shrinking for sharing.

 

1. 'Visible' light, S8612 (1.5mm) plus Baader UV/IR filter

 

2. BG25 (3mm) plus S8612 (1.5mm)

 

3. ZWB3 (1.5mm) plus S8612 (1.5mm)

 

The BG25 does look different to the 'visible' one, with softer shadows and a lightening of the sky. The magnolia buds in the tree on the left also look darker. There is a bit of a difference between the BG25 and ZWB3 one, but more subtle. I do admit it was a quick and dirty experiment though, so take from it what you will.

[colinbm]

Looking good Jonathan.

The last one looks like the old glass plates I am used to seeing in historical 1870s photos in Australia. Because they have no grain, you can blow them up forever & zoom right into them.

[photoni]

Thanks Toni, yes that is a lot of light.

Your photos are sharp & very clear, are they photo stacked ?

I have a Godox 200A that has, I hope, clear tubes.

I am needing to know how to connect via its cable to my Sigma fp full frame mirrorless camera, now full spectrum, & use it.

 

For the photos I used an old Nikkor-H 50mm f2 ... all closed at f16 ,it is from around 1965, it has only a slight anti-glare, it is not multicoated

I don't see your flash 200A on the site

http://www.godoxtech.com/products/

if it is like SK 400 from the photos I can see that it has an iridescent tube, not transparent ... if it is so it stops almost all the UVs

I use a trigger to remotely control my generators or the cable.

If you have the sync cable, you can attach it to the Sigma directly. on Dpreview.com I read about the DS [External flash ... Yes (via flash sync port)]