Circular Polarization (1 Viewer)

Prime Focus DSLR or Micro 4/3 thru ED Refractor Assy. Circular Polarizer Options ???

I have a deck facing East and slightly North, overlooking a river, where I watch birds. I live near Seattle, so we have various light challenges... overcast or clouded skies with deep green landscapes, and water. I'm not even up to the "novice" level of photography.

I'm shopping and thinking about what to get, while I save money, playing with my cheap scope and little digi-cam.

The Sun comes up and fills my living room and deck with direct light, from South, and East until about Eleven AM. Then it goes to my right rear, as I face the subjects along the river, South and West, behind the building. But, even in the afternoon, with the light from behind, and the clouds, river, buildings etc, reflecting light... I still need a Polarizer.

1. Will a more or less permanent, Circular Polarizer, be effective, or even possible, as a part of the adapter, filter, assembly between the Scope and Camera? Straight, angled, or 90 degrees? It would be more convenient there.

2. Would it be better to have a full objective sized Polarizer over the end? If so, could this effect the ED or HD qualities that I'm wanting from the Coatings on my Objective Lens?

3. While I'm at it (although I have a million questions, I'll stop here)... The DSLR or Micro 4/3 have large sensors. But with optical aberration from the scope/lens, I think I read that a "Flattener" would help utilize the full size of the sensor, bringing the outer areas into crisp focus as well. (They use this in Astrophotography). I will usually not want a "doubler;" but more likely will want, a "reducer," for near focus. Will the Circular Polarizer, Flattener, and either with Reducer or Doubler, combined, be just one thing too many?

Can it work?

OK, thanks ya'all.

Dan

Hi Dan

I do not know that polarizers will sort out your problem (I have never used them), but I do think you need a larger lens hood. The "hood" normally supplied with the scope is more like a dew shield than a proper lens hood.

My scope came with a dew shield (flocked) that extended about 6cm from the lens with 10cm aperture, and whenever the sun was anywhere near the line of sight, I lost contrast in my photos.

I used some PVC fittings (from the local hardware store) and made up a "lens hood" extending 20cm from the lens with 13cm aperture - problem solved.

I suggest that you trace the shape of the light cone entering your scope on some paper and work out the dimensions of your lens hood from there. There is a post or thread somewhere on the site that discusses the subject. I shall try and find it.

Best regards

Jaco

I've used a polarizer before, it was a 52mm one screwed into the 2" scope adapter. It did work and it works best when you are at right angles to the sun. The some light loss and so a reduction in shutter speed. You would normally use it on a sunny day so the loss in speed wasn't all that big a deal. I wouldn't keep it on all the time though.

You only need a field flattener on short focal lenght scopes as they suffer from curvature at the edges more than say a 600mm scope.

I made a very nice focal reducer for next to nothing and there's a thread on it somewhere. There's also some photos taken with the polarizer in another thread. Shall see if I can find them.

Paul.

Hi Dan

Further to the discussion above, here is the link to the thread.

http://www.birdforum.net/showthread.php?t=182146&page=5

BR

Jaco

Hi Dan

Some more stuff to enlighten you (pardon the pun).

http://toothwalker.org/optics/lenshood.html

BR

Jaco

Here's the thread on making a focal reducer. This one gives a 40% reduction and a nice flat image. http://www.birdforum.net/showthread.php?t=198161&highlight=focal+reducer This reducer allowed me to get some really nice close up flight shots of nesting Blue Tits last year. See last photo, range was about 6m at 360mm focal length equivalent.

Also a couple of comparisons on using a polarizer and not using one. The one with the very blue sky was with the polarizer and the pale sky was without. For the Robin the text is on the photo.

Paul.

Whoa.... you guys are great. I thought I'd be getting email alerts of responses.... so sorry for not getting right back here to say thank you. I am reading everything.

nobody is sillier than me... my sweety will tell you that... pun away

I don't think email alerts are on by default. Click on the 'Thread Tools' link and choose 'Subscribe to this thread'.

Paul.