[Racer X 69]

As I continue the transition to digital (this has been an ongoing process, as I started with the *iStDl and now have a K10D) I am trying to keep expenses down by integrating and reusing equipment form my film SLR cache.

I have a lens or two that work quite well, even though they don't have autofocus, etc. Like my Sigma 600mm mirror lens. With the film/digital conversion factor it is like having a 900mm focal length lens. Nice.

So the other day I was digging though some more of my film camera gear, and I stumbled across a bunch of lens filters, and thought, hey, why go out and drop more cash on new filters if the old ones will work just as well. After all, light is light, right?

Is there any reason why a polarizer for film won't work just as well for digital?

How about a sky or haze filter?

And then we get into the more specialized gear like the ones that are cut to create the "star" effects from points of light. And the various colored filters, blue, red, yellow.

So, fellow photographers, help me out, and tell me why a particular filter will or will not work just as well in the digital world.

Thanks in advance, Racer.

[dtmateojr]

All filters should be fine except the UV filter which is useless in digital cameras (it is already built in). If your polarizer is non circular type, AF will have problems.

[Racer X 69]

If your polarizer is non circular type, AF will have problems.

What does "non circular" mean?

[jatrax]

Is there any reason why a polarizer for film won't work just as well for digital? How about a sky or haze filter? And then we get into the more specialized gear like the ones that are cut to create the "star" effects from points of light. And the various colored filters, blue, red, yellow.

CPL or circular polarizers will work just fine. Linear polarizers are known to cause issues on some AF systems. Pentax has been mentioned in the past as working fine with them though but I've not tested one.

The colored filters were used to adjust the actual light to what the film was rated for. So inside with tungsten light using daylight film you needed a filter to correct. This is unnecessary with digital as the camera itself has a white balance setting that is adjusted to correct the issue. It also has an auto WB feature which is usually fairly accurate and most folks just leave it on auto

UV / Sky / Haze filters have much less utility on digital as they were used to cut out UV light which would affect film but does not affect a digital sensor. However, some have reported some utility with haze / fog by using these filters. I think they can be of minor help but I'm not sure it is enough to warrant carrying them.

If you use a filter to protect the front lens element there are now 'clear protective' filters that replace the old UV ones. I don't use a filter for this purpose but prefer to use a lens hood.

One difference worth mentioning is the coatings on the filters, modern multi-coated glass filters will not degrade your image as much as old un-coated filters will. So if you have a bunch of old filters that are from good brands then they are worth trying. But if they are inexpensive generic brand ones it might be worth it to buy new, just the ones you need.

IMHO, the only filters worth carrying in your bag with digital are a good CPL and a set of ND filters used to slow water or clouds. The ND's are available from 1 stop up to 10 stops.

[boriscleto]

What does "non circular" mean?

Most old polarizers are linear polarizers.

Polarizer - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Polarizing_filter_(photography)

[jatrax]

What does "non circular" mean?

Polarizers come in circular and linear. The circular ones have two pieces of glass attached and you turn the rings to get the polarizing effect you want. Linear ones are a single element and you do not have to turn them. Linear is usually much cheaper then circular and there are lots of them floating around used.

[rbefly]

Hi Racer,
Like you, I had (and still have) lots of film gear accessories that seemed to be going to waste with digital cameras.
After trying most of my filter selection with digital, I've come to the following conclusion; All you need are circular polarizers and occasionally a ND filter.
Color filters were more necessary with color film, if you wanted to "tint" or change a photo. Most people didn't develop or print their own color film work.
Now, suppose you want to make a sunset more "Golden". So you put the gold filter or graduated filter on and take the shot. Next you look at the finished photo on your PC, and it doesn't work right. Too gold, or the dividing line isn't in the right place. You have to hope you can correct it back to "normal" white balance in PP.
Wouldn't it be better (easier, faster, more efficient etc.) to take the shot with normal color balance and add the tint in PP?
With a filter on the lens, you have one color and one density. With PP, you have variable tint color and density, choices right in front of you.
The argument about Skylight/UV or NO filter (lens protection vs possible flare or sharpness reduction) rages on. I always used UV's on my film photography, but have used them less and less with digital. But I do use a hood on every lens, faithfully. A metal hood, I might add, except for a few DA's that came with a plastic "tulip" hood.
Bear in mind, I still shoot some film and use my YG or yellow filter with B + W film, as well as CPLs when needed.
But for digital?, Nope, no more color filters.
JMO,
YMMV
Ron

[Anvh]

CPL or circular polarizers will work just fine. Linear polarizers are known to cause issues on some AF systems. Pentax has been mentioned in the past as working fine with them though but I've not tested one.

Tested once with the K20D i believe.
AF doesnt seem noticable effected but the exposure metering was off with 1 stop both ways depending on the position of the filter.

[Racer X 69]

Well then. Thanks to everyone for the input, and the quick lesson on filters.

I have always used some kind of glass to protect the front lens element, and keep from having to risk damage to it from periodic cleaning, and will continue that practice with the digital lenses. As for the polarizers, I'm thinking that even if the old film ones work, giving a newer type a go may be worth the added expense.

Great point about the post processing/pre processing decision. Once a decent image has been shot, it can be manipulated endlessly with the editing software of your choice.

As far as the lens hoods goes, I find I have to remove the hood on the 18~55 DA kit lens when using the camera's built in flash, or the hood creates a shadow in the image, even when using the flash for fill in daylight shots. But if I am not using a flash I always have the hood in place.

Polarizers come in circular and linear. The circular ones have two pieces of glass attached and you turn the rings to get the polarizing effect you want.

I have a Tiffen polarizer from the film days that has a handle to rotate it, to adjust the degree of polarization. So would that be the circular type?

Linear ones are a single element and you do not have to turn them.

Based on my understanding of light and how it is affected by a polarized filter (or even polarized sunglasses) rotating the glass in relation to the direction of the sunlight is how the light is polarized or un-polarized. So how would a single element polarizer be useful if it could not be rotated?

[Anvh]

Based on my understanding of light and how it is affected by a polarized filter (or even polarized sunglasses) rotating the glass in relation to the direction of the sunlight is how the light is polarized or un-polarized. So how would a single element polarizer be useful if it could not be rotated?

They rotate but they filter the light differently.
Since the AF and the light meter, meters off from the mirror that means that the polarizer change the reflection off the mirror, changing exposure and the AF.
Polarizers - Optical Filters

[boriscleto]

All about Polarizers - Linear and Circular

You can also easily tell if a polarizer is linear or circular even if it is not marked. Hold the polarizer about 2 or 3 inches in front of your eye, and look at your reflection in a mirror. Looking from the camera's viewpoint (i.e. with the filter threads pointing towards you) you should see the image of your eye in the mirror (as if looking through a neutral density filter). Now turn the filter around so that the filter threads point at the mirror. If the polarizer is linear you should see the same thing that you saw before, but if it is circular it will appear black and you will not see the reflected image of your eye. This is because light reflected from your eye passing through the circular polarizer exits in the direction of the mirror as circularly polarized light (let's say it's left handed circular polarization). When it reflects from the mirror it reverses its polarization to the opposite sense - in this case it is reflected as right handed circular polarization. The filter only passes left handed circular polarization when the light enters from the "camera side" of the filter, so the reflected light is blocked. The situation is analogous to the effect of a vertically polarized linear filter on horizontally polarized light - little or no transmission of the light can occur.

It is most likely a linear polarizer unless it is labeled as a circular polarizer.

[dms]

If your purpose is to use what you can, try your linear polarizing filter and see if it works OK. A good circular one will cost as much as a reasonably good lens--and likely the linear one will work fine. My experience with pentax k20d is it works perfectly. And if it means a minor exposure adjustment, that's easy to do when you use it.

[JimJohnson]

There are a few other filter types that might be useful on a dSLR - although the effects can often be simulated in post processing. These include starburst filters, softening filters, basically anything that alters the image in ways other than color. And truth be known, even colored filters could be useful if the photographer doesn't use automated white balancing.

Like most of the posters, I keep CPL filters in my go-bag, and I carry UV filters as well - but only use them in really tough environmental situations to protect my lenses front elements where a lens hood cannot.

[sunglint]

Polarizers come in circular and linear. The circular ones have two pieces of glass attached and you turn the rings to get the polarizing effect you want. Linear ones are a single element and you do not have to turn them. Linear is usually much cheaper then circular and there are lots of them floating around used.

This is not correct. A linear Polarizer (usually a type PL) is a glass element that rotates on a glassless base, rotated to block the reflections from a certain direction. The OPs old polarizer would be this kind. You put it on the camera and rotate it to get the desired effect. I tried my old PL filter with my K-01 and it had a very real difference, I made this post in the K-01 forum to demonstrate both polarizer and IR filters. Of the two at the top, you can see that the exposure barely changed, but the effect of rotating the filter was significant. I did not attempt to autofocus, I was using an MF lens anyways.

I haven't used a Circular Polarizer (type CPL) yet but just ordered one so will find out.

As mentioned most of the old filters will be compensating, i.e. fluorescent lights, yellow for contrast with B/W film, etc. If you shoot in RAW then you can adjust all this afterwards, or do a manual white balance at the time. Protecting the front element is still a good idea.

[Anvh]

With the K-01 you can use linear without any need to worry since it doesnt use any mirrors internally.