Spectroscope

[photoni]

to get to know my lenses is better an cheap spectroscope like this useful or is a gratings 1000lm ?

 

<p>LINK<br>https://www.amazon.com/dp/B00MNEAMF4?ref=ppx_pop_mob_ap_share</p>

 

[colinbm]

You won't be able to see the UV spectrum with your eye.
 

[dabateman]

You will need to attach either option to a camera,  and calibrate it with a known light source like a Mercury bulb.

Then you can measure your lenses.

You might want to read up on some diy spectrometry first and see if there are software tools you can use.

[photoni]

2 hours ago, colinbm said:

You won't be able to see the UV spectrum with your eye.
 

yess ... I saw an article by Dmitry, with many interventions, I wonder what is the easiest and most understandable thing for a dinosaur like me.

 

[colinbm]

If you look in my Flickr photostream you will see an Amisi Prism Spectroscope mounted on a lens.
The advantage of the Amisi Prism Spectroscope for UV is that the size of the UV spectrum is wider then the IR end.

 

[dabateman]

Photoni you can stop here and just enjoy the images your lenses provide. With the filters you care about. 

 

Or you can jump down the never ending rabit hole of filter and lens testing to determine what they are.

This may start out as simple tests that you are unhappy with until thousands of dollars slowly spent over time accumulates to still being unsure about you equipment. 

It all starts with some cheap diffraction grating and a pinhole lens.

Unless you like the rainbow images and then you can work with them.

[colinbm]

Good advice Dave, spectrums can be addictive....

[photoni]

hey boy hey friend, I already fell into the black hole ... of ancient things
and I can't put that straw in front of my 4 300mm lenses
I just want to understand how far they see it in the simplest way.

[Andrea B.]

Che bella, questa machina!

(How beautiful, this camera!)

---

 

 

You could remove the lens and try the Pinhole Test for UV transmission.

It is, of course, not precise, but does give some indication of UV capability.

 

References:

 

Hornblende: Pinhole and Relative Brightness

01 Apr 2017

http://www.ultraviol...dpost__p__15820

 

See also

A.S.: Pinhole and Relative Brightness

08 April 2017

http://www.ultraviol...dpost__p__15941

 

See also

Andrea B.: Pinhole Test Protocol Summary

10 Apr 2017

http://www.ultraviol...dpost__p__15964

[photoni]

For my big lenses ... is this okay?

https://www.ebay.it/itm/254183540070

[JCDowdy]

Well, it says, "Encapsulated In Its Own Laser Cut Acrylic Display Case", so is that going to be UV transmitting acrylic?

[photoni]

31 minutes ago, JCDowdy said:

Well, it says, "Encapsulated In Its Own Laser Cut Acrylic Display Case", so is that going to be UV transmitting acrylic?

I think it's a simple "Hasselblad type" projection frame
the film can be removed
there are also very large measures without protection

[dabateman]

I think this is the stuff I bought: 

https://www.ebay.com/itm/280859388704?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=uZ1NYTrrT8m&sssrc=2349624&ssuid=RxqKLNPYQr-&var=&widget_ver=artemis&media=COPY

[photoni]

33 minutes ago, dabateman said:

I think this is the stuff I bought: 

https://www.ebay.com/itm/280859388704?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=uZ1NYTrrT8m&sssrc=2349624&ssuid=RxqKLNPYQr-&var=&widget_ver=artemis&media=COPY

Dave
maybe it is the right one to do a test by applying the A7 (plus TSN575+Zwb1) on the back of the Toyo 4x5 with my  light , flash

it's just a curiosity to test the lenses for the large format

I have three 300mm (f: 4 and 4.5 and 5.6) two 360mm (f: 4.5 and 6.8) - two 400mm (f: 4.5 and 8)

 

P.S.

yes ... I just bought it

[colinbm]

Toni, notice that the light has to enter at an angle, so you will need to have the grating at an angle to the lens so that the light path is straight down the lens.

[photoni]

is arrived  the "diffraction Grating Sheet Linear 1000 lines / mm" ... in a roll without protection without support, with many dents :(
I immediately did a test to understand how it works with A7 + Takumar 35 f3.5 and flash light ~ 125W

 

three exposures
the first three out of focus
F.S. - with TSN575 + ZWB3 - with Hoya R72     QB29
the other three with focus on the reticle.

not having Fraunhofer lines I have no references, but it is clear that the Hoya R72 filter sees IR but also UV ... really strange.
the UV stack has a slight IR loss

[ulf]

1 hour ago, photoni said:

but it is clear that the Hoya R72 filter sees IR but also UV

That might not be true.

What you see here might more likely be a second order diffraction of the input light.

 

Diffraction gratings can give many confusing results like this with two overlapping spectra.

Advanced professional spectrometers with gratings often have special gradual cutoff filters to eliminate this phenomenon.

A proper Hoya R72 do not transmit UV.

[photoni]

17 hours ago, ulf said:

What you see here might more likely be a second order diffraction of the input light.

 

I too have the doubt that it is a secondary ghost,
with the UV stack in the 5th photo the second has the same colors.

 

the flash is not a point light
it has a circle tube, and an internal wave reflector.

 

it is however strange that the "second" with Hoya R72 has different colors.

 

I have to try it with the sun, but these days there are beautiful clouds interrupting it.

[colinbm]

If you don't have a slit, you can reflect the light of a pin or needle to give a thin line. The light will need to behind you, which has its advantages, particularly with the Sun or any other bright source.
https://www.animations.physics.unsw.edu.au/labs/diffraction/diffraction-labs.html

 

[Nate]

@photoniI have a cardboard covering my south facing old school window, with a square cut out and made a black piece and put a slit, about an inch and half in there. If you aim your camera through the slit, about 4-5 ft away(80mm lens) from it making sure all you see is the sky and focused well on the slit. hold the diffraction grading on the end of your filter with the 1000 line wording on top, and the wavelength numbers on the bottom of the grading, pan your camera to the right till you see the spectrum. The UV will be first on the left. you might need to tilt the gradings right side a bit toward the window to get it sharp, but it works for testing. here's a quick one I did with the Baader/zwb1.

[photoni]

there is an error .... I have to re-test

 

 

 

[photoni]

the previous test is wrong

this is the chart of my set

I redid the test only with flash at night, without ambient or artificial lights ... it seems to me that there are no duplicated images

now it all seems logical

I hope to do tests with sunlight soon

Thanks

Antonio

[photoni]

I'm probably old and dumb
I can't find "Fraunhofer lines" ....... (the sun has not come)

in the studio I have two lights, one NEON and one LED
the difference is interesting!

[Stefano]

Actually your "neon" lamp is a mercury lamp, and most of those lines (I think except for the red ones) are mercury lines. The red lines come from the phosphors inside.

 

Some electrical switches have an orange lamp inside, and that usually is a neon lamp.

[Nate]

I can only get lines if I use a home made spectrometer for inside. It's got to be the distance from your camera to the slit, or the distance to the light source. I'm trying to figure this out too, as I'd like to use my camera instead of a FS Webcam for indoor sources. Here's what I made yesterday, kind of works for indoor and outdoor.