Protecting the white balance target?

[Doug A]

My white balance target is a thin board wrapped in plumber's tape. Performs well enough, but it is fragile. Would it work to place the target inside a CD case and take the reading thru the plastic? CD cases are supposed to be transparent to UV.

 

Thanks,

Doug A

[Andrea B.]

Who knows?? Try it and see what happens.

 

You could store the target in the CD case and open the case when you use the target.

 

 

[OlDoinyo]

If it works you could just line the inside of the case with the tape and use it that way.

[ulf]

9 hours ago, Doug A said:

My white balance target is a thin board wrapped in plumber's tape. Performs well enough, but it is fragile. Would it work to place the target inside a CD case and take the reading thru the plastic? CD cases are supposed to be transparent to UV.

 

Thanks,

Doug A

It would not be optimal as the PMMA of the case has surface reflections. An ideal target should have a matted surface, not generating any specular reflection. Also Not all PMMA is that good at transmitting UV and the case can also have built in material stress from the injection moulding that can give polarisation effects. How much all this matters is difficult to tell. It might be good enough for your needs.

 

WB targets range from the cheapest to very expensive ones like the Spectralon reflectance reference targets. 

[Nate]

I think just having it in the case and open when needed.  I have mine in a small plastic bag that I take out each time.

[Andy Perrin]

Yeah, I have a circle of teflon in a little filter case. I open the case, take a white balance, and then close it up again so it doesn't get too dusty. I don't think doing it through the plastic is necessary or a good idea (for reasons already mentioned above).

[Guest]

Doug, It's actually the plumber's tape that is protecting your wallet from the Spectralon. 

[dabateman]

Just treat yourself to a real piece of virgin white PTFE off Ebay.  Buy large and cut it to the size you want. Get it at least 1/4 inch or 6 mm thickness. 

 

[ulf]

2 hours ago, dabateman said:

Just treat yourself to a real piece of virgin white PTFE off Ebay.  Buy large and cut it to the size you want. Get it at least 1/4 inch or 6 mm thickness. 

 

Then make the surface matted with a coarse grit water sanding paper, like 220 or 300, working at the PTFE in random directions.

When ready, you should see very little specular reflection when bouncing light from a light bulb at the slanted PTFE sheet.

Try that surface bounce before grinding too, to get an idea of what you are looking for.

---

PTFE is partially translucent and 6mm is a safe thickness to be both stable and not affected through the sheet

 

Spectrolon is a fancy extra porous super pure PTFE-material that is quite expensive.

It is used in traceable laboratory reflectance references.

 

That level of excellence is normally not needed for WB, but it is a good idea to look for "virgin" PTFE when buying the sheet.

[Andrea B.]

Ulf, I am making a note to add your suggestion about matting the PTFE surface with sand paper to the White Balance sticky.

 

 

 

[Doug A]

17 hours ago, Andy Perrin said:

Yeah, I have a circle of teflon in a little filter case. I open the case, take a white balance, and then close it up again so it doesn't get too dusty. I don't think doing it through the plastic is necessary or a good idea (for reasons already mentioned above). Filter case is a good idea!

14 hours ago, Blazer0ne said:

Doug, It's actually the plumber's tape that is protecting your wallet from the Spectralon. 

Good point.

Great idea. Never thought of opening the case prior to setting the custom WB. 

Thanks,

Doug A

[Doug A]

11 hours ago, dabateman said:

Just treat yourself to a real piece of virgin white PTFE off Ebay.  Buy large and cut it to the size you want. Get it at least 1/4 inch or 6 mm thickness. 

 

I'll have to track that down on the bay. Thanks..

 

8 hours ago, ulf said:

Then make the surface matted with a coarse grit water sanding paper, like 220 or 300, working at the PTFE in random directions.

When ready, you should see very little specular reflection when bouncing light from a light bulb at the slanted PTFE sheet.

Try that surface bounce before grinding too, to get an idea of what you are looking for.

 

---

PTFE is partially translucent and 6mm is a safe thickness to be both stable and not affected through the sheet

 

Spectrolon is a fancy extra porous super pure PTFE-material that is quite expensive.

It is used in traceable laboratory reflectance references.

 

That level of excellence is normally not needed for WB, but it is a good idea to look for "virgin" PTFE when buying the sheet.

Hadn't considered making the target a matte surface. Thanks for the sanding tips..

Thanks everyone,

Doug A