Three UVA Dichroic Filters in Sunlight with a Sunflower

[Andy Perrin]

Colin, how are you doing the white balance on the PTFE? It looks very green and if you did a white balance on it, it should look white/gray. I am wondering if the PTFE reflects so well that it’s saturating the sensor when you do the WB and gets a bad reading.

 

I think your spectrum mostly matches what I remember of the SEU although I don’t recall how the different versions changes.

[colinbm]

Thanks Andy

I opened it up in PN again & did another click WB & it looks better.

I will have to see what changes in the CWB happen in camera with different exposures & see what I can learn ?

Other then that I will from now on do a second click WB in PN, if I can. Sometimes PN shows a red circle with a red diagonal line & won't change the WB, I guess this is because it is happy with what it is seeing.

The SEU Gen3 is showing a vignette where the other two, the BaaderU & SEU Gen1 don't.

 

Anyway here is the same photo with a second click WB in PN......

 

[Andrea B.]

Photo Ninja cannot make a proper highlight recovery when white balance is attempted on an area which has a two-channel or three-channel blowout. So PN displays that red circle with the diagonal through it to indicate a refusal to perform white balance.

[colinbm]

Photo Ninja cannot make a proper highlight recovery when white balance is attempted on an area which has a two-channel or three-channel blowout. So PN displays that red circle with the diagonal through it to indicate a refusal to perform white balance.

 

Thanks Andrea

I will have to learn this protocol for taking a CWB with a manual lens & getting the exposure correct first, then a CWB.

Auto lenses don't have this problem...perhaps ?

[rfcurry]

Col,

Why are you putting an S8612 over the SEU Gen3? If you want to see if there is an IR leak, just put an R72 over the SEU Gen3 (and also try it with the Gen1 and the BaaderU).

 

Thanks.

[colinbm]

Dave thought it might help...

Now I am getting a better CWB, I'll try again with out it.

I was hoping it might knock down the vignetting a bit.

I have some gear coming so I can fit a filter behind the lens, I am hoping it will work better then.

[rfcurry]

Mounting the filter behind the lens is an excellent idea, if you can do it. I've wanted to try that but haven't found a mechanism, yet, that allows easy exchange of filters behind the lens. I like being able to pop a filter off and another on, one-handed. Otoh, the nearly collimated light behind the lens will eliminate all the dichroic issues.

[colinbm]

Thanks Reed

With the converted Sigma fp camera, full frame, mirrorless with a Leica L-mount there are a ton of accessories & there is a Russian guy that makes good gear, but getting it takes a long time, over 6 weeks & still waiting for Air Mail.

I'll post the arrangement when I get it set-up......soon....

[dabateman]

Mounting the filter behind the lens is an excellent idea, if you can do it. I've wanted to try that but haven't found a mechanism, yet, that allows easy exchange of filters behind the lens. I like being able to pop a filter off and another on, one-handed. Otoh, the nearly collimated light behind the lens will eliminate all the dichroic issues.

 

Reed in your last couple of posts I noticed the m43rds Panasonic camera. This might be an option for you:

https://www.bhphotovideo.com/c/product/1190854-REG/deo_tech_deoowlef2m431_owl_canon_ef_lens.html

 

Here is a review of the drawer by Pedro. Olympus cameras need an adjustment due to the fake pentaprism box:

https://www.photo-spectrum.info/2020/06/a-lens-adapter-with-a-filter-drawer/

 

Mount adapters to EF mount are cheap. You could add a M42 to it easily and a helicoid to your lens.

 

I thought I was seeing IR brown in Colin's SEU3 shot so suggested to try the S8612. But maybe was just the white balance issues he has been having recently.