Red Filter for PT-033

[bfisher]

In topside photography, UV filters are often used just to protect the main lens from dust and scratches. It's really just using a relatively cheap piece of clear glass to protect the expensive stuff.

In the case with the magic filter mentioned above, they are just being used to hold the filter in place.

That sounds simple enough. Now the second part. Who would make any that fit the PT030 housing?

 

[Charlie99]

Simple questions are the only ones I can answer.

There's a pretty good chance that just about any photo shop, even chain stores like Wolf Camera or Ritz Camera will have a UV filter of the right size. Obviously, a larger camera store gives you an even better shot at finding one.

You can carefully measure the diameter of the port on the your housing. Or more simply, just bring it with you and verify the right sizing right there on the spot.

 

[bfisher]

Simple questions are the only ones I can answer.

There's a pretty good chance that just about any photo shop, even chain stores like Wolf Camera or Ritz Camera will have a UV filter of the right size. Obviously, a larger camera store gives you an even better shot at finding one.

You can carefully measure the diameter of the port on the your housing. Or more simply, just bring it with you and verify the right sizing right there on the spot.

I think you gave me a pretty simple answer to a pretty simple question. I'll have to give it a try. And for what it's worth, I can only understand pretty simple answers.

Thanks.

 

[Charlie99]

I just came back from picking up mail. This thread reminded me that I wanted to try out a magic filter. Ordered Saturday 8/25. Arrived from the UK-based supplier the following Thursday or Friday.

I hope to do some tests on the relative insertion loss in the R, G, and B channels and post the results in a couple of days.

 

[Dee]

Sorry for the delay....Charlie is exactly right. The UV filters is just the convenience of already having clear glass in a screw mount to serve the purpose. I want to make one for my PT-34 but don't know the exact size. I *think* I've measured it correctly but I'll take the housing to a big camera shop to size it correctly.

Charlie...I'm looking forward to your results.

 

[bfisher]

You know what? This is starting to make some sense to me. I heard some time ago (years?) that sunglasses with glass lenses didn't need UV coating because glass has UV filtering by nature.

So what you guys are saying is that UV filters for cameras are basically clear glass intended mainly to protect the camera lens from harm. True?

See, now I'm starting to get edumacated. Thankyou all.

Oh, my Magic Filters just came in the mail today. I think it was 8 days from the UK to Pa. S/H was $18 cheaper than a place in North Carolina.

 

[DesertEagle]

The PT-030 has a rubber shroud inside the lens barrel. Remove the shroud and cut the filter using the stencil. Put the filter into the barrel/lens port. Then re-insert the shroud. The shroud will keep the filter in place. The tricky thing is lining up the shroud. You'll know if you've done it incorrectly, because the lens won't extend fully. It's pretty easy.

 

[bfisher]

DE, thankyou. I see what you are saying about the shroud. I still think I'm going to try to fit up with UV filters. I want the option of removing the filter and using my strobe.

Thanks.

And I apologize to everybody for one thing. This thread started out asking about the PT033. I missed that and guess did some hijacking. I am greatful for all the help, however.

Barry

 

[Charlie99]

Here's some tests on the tranmission characteristics of the AM1 Auto Magic filter, as well as an 81A warming filter and a Red 25A filter.

After trying a few different methods, I finally came back to the simple technique of

1. Put Olympus Stylus 410 point and shoot in Bright Sunlight white balance
2. Do an exposure hold on a sunlit Kodak white card
3. While maintaining exposure hold, slip the filter to be tested in front of the lens
4. then take photo.

Then I looked at the photos in PhotoShop Element Info pallette to get the RGB values.

With the combination of lighting and WB, the white card typically had RGB of 170/170/170.
The white card through the AM1 was about 154/50/40
Through the 81A was 155/140/119 (no filter reference for this later test was 165/162/153)

Through the red 25A the white card was 133/0/1 !!! No wonder it didn't work when I tried it. Virtually NO green or blue gets through.

The RGB outputs through the AM1 were 0.9/0.3/0.25 relative to no filter. In other words, the filter had about 10% loss in red, 70% in green, and 75% in blue. Assuming that the camera exposure would go up slightly to compensate --- the relative transmission of R/G/B the the AM1, normalized to the red channel is 100%/32%/26%.

In other words, relative to the red, the AM1 reduces the green by about a factor of 3 and the blue by about a factor of 4.----------------------

Since I had one handy, I also tested the 81A "warming" filter. It had about 6% loss on the red channel. Normalizing to the red channel, the green was reduced only about 10% and the blue about 23%. Even stacking up 3 81A filters on top of each other still wouldn't cut the blue and green as much as the AM1, while the loss on the red channel would be much more.

-----------

Unfortunately, my travel plans won't let me get to tropical waters for a couple of months, but others have already shown that you can get pretty good results. I just wanted to know why the 25A I tested did so horribly --- the reason is pretty simple: it lets nothing but red through, and almost completely kills the green and blue channels.