Linear polarizer, auto focus and metering with SLR.

[royent]

Surely the obvious thing to do is stick it on and try it, or am I missing something?
Roy

[William W]

To bring new life to this thread...Linear polarizers weren't called linear until the proliferation of circular polarizers made it necessary.

On this statement, I agree.

I read the statement as meaning - It was only after the flood of CPL in the marketplace that the original “Polarizing Filter” got re-named “Linear Polarizing Filter”. Prior to ‘the proliferation of’ Circular Polarizer Filters (CPL), the term “Polarizing Filters” was used to refer to (what are commonly know termed) Linear Polarizing Filters.

Certainly, there was (always) a differentiation made for a Circular Polarizing Filter, as Manfred has outlined; but in 1960~1970 there were, by comparison, not very many CPL compared to the number of PL Filters on the market.

This is evidenced by Manfred’s reference to (specifically) “Circular” Polarizing Filter in the Leica User Manuals: I cite a similar dated reference source, The (Ilford) Manual of Photography 6th Ed. 1971, pp. 306~315, where the Manual discusses “Polarizing Filters”; there is no mention of “Linear” though it is obvious that linear polarizing filters are the exclusive topic.

There are many other sources from that era only using the term “Polarizing Filter” and not using the qualifier “Linear".

My library is extensive, though by no means complete, the earliest Text Reference to “Circular Polarizing Filters”: is found in, Handbook of Optics, 2nd Edition, Vol. 2 Bass M (McGraw-Hill), (1995), Ch.3, p. 49. My bold and underline now for emphasis:

“There are also some novel circular polarizers and polarization rotators for use in the far ultraviolet (see the papers by McIlrath ,162 Saito et al . ,268 and Westerveld et al .269 ) , far infrared (Richards and Smith ,270 Johnston ,271 and Gonates et al .272 ) , and visible region (Lostis ,273 and Greninger274)” (op. cit).

Note the use of the word “novel”, a word often used in classic technical texts meaning “new and different”.

It seems to me that whilst Leica was making specific reference to Circular Polarizing Filters in the 1970s, this was for the purpose of differentiation to what was then termed a “Polarizing Filter” (i.e. NOT a Linear Polarizing Filter) and even in the 1990’s a CPL was not necessarily a mainstream product.

WW

[Manfred M]

Just to keep things even more interesting, circular polarizing filters were also referred to as quarter-wave plate polarizing filters. This was the terminology in some university physics textbooks back in the early 1970s.

[William W]

^ Yes, in the same vein, the book "Handbook of Optics" is not specifically about Photography per se, more like a physics text.

[rpcrowe]

In 1968, I had a Pentax ME SLR and was experiencing a horrific time getting decent exposure when I was using a polarizing filter. A Tiffen representative came to my Navy unit (Pacific Fleet Audio Visual Command) and I asked him what the problem was, That was the first time I heard about a circular polarizer. The representative sent me a CPL in the mail and my exposure problems ceased...

I haven't been using CPL filters as much now as I used to. In fact, although I have CPL filters for my mirrorless camera lenses, I haven't used one yet.

[azkitch1]

Ted, I'm just going to dig out a 49 mm polarizer and put it on my old Vivitar macro lens attach it to my Sony and see what happens. See if it seems to meter correctly since I have to focus it anyway

[azkitch1]

Yep, Roy, that's it.

[Manfred M]

Ted, I'm just going to dig out a 49 mm polarizer and put it on my old Vivitar macro lens attach it to my Sony and see what happens. See if it seems to meter correctly since I have to focus it anyway

You can also shoot in manual mode and use your histogram to determine the correct exposure. If all you are concerned about are the automated functions, you can definitely get around the issue that way.

[azkitch1]

You can also shoot in manual mode and use your histogram to determine the correct exposure. If all you are concerned about are the automated functions, you can definitely get around the issue that way.

There's a subject for another day...I've watched a bunch of Capture One tutorial videos and one or two Webinars, and I cannot figure out what the histogram is trying to tell me. It may as well be Calculus...

[Manfred M]

There's a subject for another day...I've watched a bunch of Capture One tutorial videos and one or two Webinars, and I cannot figure out what the histogram is trying to tell me. It may as well be Calculus...

So what's wrong with calculus?

A histogram is a representation of what your camera has captured (with some caveats). The important thing is to try to ensure that you have limited values at either extreme to ensure that no data loss has occurred. If you are concerned about the shape and position of the data, that's relatively unimportant. If there is a choice, expose as far to the right as possible without clipping the highlights as this will give you less digital noise to worry about.

[DanK]

There's a subject for another day...I've watched a bunch of Capture One tutorial videos and one or two Webinars, and I cannot figure out what the histogram is trying to tell me. It may as well be Calculus...

I haven't looked at their explanations of histograms, but if you understand what a bar graph or histogram is in general, you are pretty close to understanding the histogram in postprocessing. It doesn't require complex math, at least if you ignore scaling.

The range of dark to light--pure black to pure white--is represented by the values at the bottom of the histogram. For simplicity, I'll treat this as discrete, even though it isn't. Scan the entire image and collect every pixel with values between 0 and 1. Stack them up at the left. Now collect all the pixels with values between 1 and 2, and stack them up next to the first stack. If there are more of these than 0-1, the pile will be higher. Keep going until you do this for 254-255, the brightest pixels. The height of each stack tells you how many pixels are in that range of brightness, anywhere in the image. It says nothing whatever about where those pixels are.

This would be easier to explain if I could add some graphics, but I don't have any handy at the moment.

So, suppose that you have a histogram that has a big peak on the far left and not much elsewhere. That simply would tell you that most of your image--most of your pixels--are very dark. If you have a stack up against either end, then you are "clipping"--exposing lighter or darker than the camera can capture. If you have everything in a small range of values in the middle, then you have no really dark or light areas, and the image will be lacking in contrast. In that case, you could add contrast by making some of the relatively bright areas even brighter--moving the right end of the histogram farther to the right--and by making some of the relatively dark areas even darker--moving the left end of the histogram farther to the left. And so on.