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How to use photographic filters
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PostPosted: Tue Mar 27, 2007 4:16 pm    Post subject: How to use photographic filters Reply with quote

Please teach me guys how can I use right different photographic filters! What filter for what purpose ? Thank you!


PostPosted: Tue Mar 27, 2007 4:32 pm    Post subject: Reply with quote

oh, that's a wide range question!
Let's first see what filters. Color correction filters?

You can use those in two ways:
- by "naked eye", you determine how cool/warm the natural scene is and use an amber or blue filter to balance it
- by use of a thermocolorimeter - then you can determine the filter needed with precision

Then there are many other kind of filters:

- polarizer
- gradient
- neutral density
- diffusers
- B&W filters
- special effects etc.

So impossible to give a one-for-all answer!

The one thing that I can say is: keep in mind that a filter, ANY filter (yes including the skylight or UV filters) causes a small (or large) degradation of the image quality.

So as a general rule: the less filters you use, the better.


PostPosted: Tue Mar 27, 2007 5:02 pm    Post subject: Reply with quote

Filters are great for film cameras.

For DSLRs only these filters are useful:

- Skylight- or UV-filter to protect the lens in tough surroundings
- Greyfilter to get to longer exposure times or open apertures even if it is bright.
- gradient filtes in high contrast situations (sky / landscape)
- polarization filters to intensify colours and to filter away reflections (e.g. on water)
It is an art to use pol.filters correctly.

Colour filters are IMHO nonsense for a DSLR, since the auto white balance will calculate away the effect. And if you want this kind of effect, you can easily do that with PS (or similar pp).
Those colour filters were and are essential for b/w film photography.

Carsten


PostPosted: Tue Mar 27, 2007 8:02 pm    Post subject: Reply with quote

Thank you guys! I read on skylight filter title this is good for outdoor portraits , is it true ? I also read for DSLR need circular polar filter, not old linear polar filter. Is this a commercial only or need to change really to the latest one?


PostPosted: Tue Mar 27, 2007 9:21 pm    Post subject: Reply with quote

Attila wrote:
Thank you guys! I read on skylight filter title this is good for outdoor portraits , is it true ? I also read for DSLR need circular polar filter, not old linear polar filter. Is this a commercial only or need to change really to the latest one?


The skylight filter is useless with digital cameras, because the camera will balance the white anyway.
The only purpose for a skylight filter would be to protect the front lens, if you are useing an expensive lens.
For this purpose, it's better a UV filter, or even a totally neutral "protection filter".
But keep in mind that a filter will of course increase the risk of flares, especially if the UV filter is not very good.
So the UV filter needs to be a very good one. B+W are the best ones, but are very expensive. On the other hand, there is not much point in spending one or more hundreds of euros for a lens and putting in front of it a Eur 5 UV filter that will ruin the optical quality.
Due to the way sensors are designed (but don't ask me the details) they say that digital cameras need a particular type of UV filters. For this reason (or for simpe marketing?) all the filter companies have released recently special UV filters for digital cameras.
I never use UV filters, unless I am using lenses that I bought new. In this case, I always keep the UV filter on, because to have a "like new" glass will largely increase the used value of the lens if you want to sell it.

As for polarizers, what I have read is different: I read that it's the autofocus cameras (film and digital) that need circular polarizers, because of the way their internal light meters work.
I have both circular and linear, and I can tell you that yes sometimes I have perceived a metering error when using linear polarizer on autofocus cameras, but 90% of the time, I didn't.
Another thing to keep in mind is, the effect of a linear polarizer is stronger than the effect of a circular polarizer.
I rarely use polarizers, due to my own style which does not blend well with them, but the rare times I do, I always use a linear polarizer, because in my opinion, it saturates the colors better than the circular polarizer.


PostPosted: Tue Mar 27, 2007 9:32 pm    Post subject: Reply with quote

Quote:
Another thing to keep in mind is, the effect of a linear polarizer is stronger than the effect of a circular polarizer.
I rarely use polarizers, due to my own style which does not blend well with them, but the rare times I do, I always use a linear polarizer, because in my opinion, it saturates the colors better than the circular polarizer.


Great I have only linear polarizer, I also bought protection filter only for new AF lenses and I removed filters from MF lenses.


PostPosted: Wed Mar 28, 2007 12:38 pm    Post subject: Reply with quote

I agree with Orio.

I only use any kind of protective filters with brand new (and expensive) lenses.

BTW, you should always spend more money and buy the best filters you can get. Here any money saved will cause quality reduction. With very good filters I cannot see any difference.

And, although I've read about a test where they found out that mostly linear polarizers work with a DSLR, you should use circular ones, really.

The metering system might not work properly when uses with polarized light in one linear dimension.


PostPosted: Wed Mar 28, 2007 1:40 pm    Post subject: Reply with quote

LucisPictor wrote:

And, although I've read about a test where they found out that mostly linear polarizers work with a DSLR, you should use circular ones, really.
The metering system might not work properly when uses with polarized light in one linear dimension.


Yes, but with the digital reflex we have a great chance: we can see the histogram right after shooting, and if needed, we can adjust and reshoot.
So on film I would always recommend the circular, but on digital, it really depends only on how much time you plan to dedicate to take a better picture.


PostPosted: Wed Mar 28, 2007 3:59 pm    Post subject: Reply with quote

LucisPictor wrote:
Filters are great for film cameras.

For DSLRs only these filters are useful:

- Skylight- or UV-filter to protect the lens in tough surroundings
- Greyfilter to get to longer exposure times or open apertures even if it is bright.
- gradient filtes in high contrast situations (sky / landscape)
- polarization filters to intensify colours and to filter away reflections (e.g. on water)
It is an art to use pol.filters correctly.

Colour filters are IMHO nonsense for a DSLR, since the auto white balance will calculate away the effect. And if you want this kind of effect, you can easily do that with PS (or similar pp).
Those colour filters were and are essential for b/w film photography.

Carsten


Must agree 100% with Lucis
Using a colour filter with digital is nonsense. Even with BW film that is being scanned to the computer, it is doubtfull they do any better than doing the effect PP.

I wouldn't go for any gradient filter either. It was a blanket uncontrolable effect. Far more and better control to shot RAW and then work with two layers or use PS own gradient

Polarizing filter is a must. I never had any problem using them.

Natural density filters (Grey filters) Also a big must and My most used filters. How else can you control exposre when the the iso won't go any lower? Essential for shooting shallow depth of field and when slower shutter speeds are required

Special effects filters (Many good Cokin ones) great fun and some fantastic results and be obtained from them. gallaxy, diffraction, soft focus various, star, various. Not gradient or colour special effets though

UV for protection but they also do cut through a bit of haze particularly when using telephoto. I have done endless little tests and the only time I have ever seen them have any ill effect on an image is when shooting into the light and catch some flare. Which
shouldn't hapen if you use good lens hoods.

Lens Hoods. Most important if you want the best from your lens. I often stick a rolled up sheet of black cardboard on my 300mm about 5/6 inches of lens hood. lens hoods aren't only or shooting into the light they work with every shot.


PostPosted: Sun Apr 01, 2007 9:14 pm    Post subject: Reply with quote

For the reason Orio mentioned about degrading images, I have never, ever, used a filter in battle. One or two have arrived on lenses I've bought and I've kept them on for protection, but they come off for taking pictures.

So, after reading an article about polarising filters, I was intrigued to find out more and I bought a cheapish Hoya circular pol. filter to try.

I have never seen one like it before. The glass is dark-tinted, like sunglasses - the meter is telling me this makes a difference to the exposure of at least 2 stops. In fact it has two tinted glasses, one static next to the lens and one that is free to rotate. I see no effect when I rotate the outer glass except that some reflected light is (almost) eliminated. I was expecting the rotation to create a gradual reduction in light down to virtually nothing, but that doesn't happen. I also see no difference in colours, like I do with my pol. sunglasses, and that's disappointing because it is what I was hoping for.

I confess I don't understand this filter or know how to use it properly. No instructions came with it. Can anyone kindly give me some pointers?


PostPosted: Sun Apr 01, 2007 10:04 pm    Post subject: Reply with quote

Hi, Peter!

Make sure that you stand in the right angle to the sun if you use a pol.filter to make most of the effect:
"Polarization is most effective at 90 degrees to the sun. This means that the subject that you are shooting will display maximum polarization at right angles to the sun's position. At 180 degrees, in other words with the sun right behind you, polarization is almost non-existent."
(Source: http://www.luminous-landscape.com/tutorials/polarizers.shtml)

See also:
http://en.wikipedia.org/wiki/Polarizing_filter#Polarizer
http://www.shooter.net/index.php/weblog/Item/using-a-polarizer/
http://www.weatherscapes.com/techniques.php?cat=general&page=filters
http://www.stevesforums.com/forums/view_topic.php?id=62980&forum_id=50

Enjoy!

Carsten


PostPosted: Sun Apr 01, 2007 10:25 pm    Post subject: Reply with quote

Thanks very much Carsten! That's just what I need Smile


PostPosted: Sun Apr 01, 2007 10:30 pm    Post subject: Reply with quote

You're welcome, mate!


PostPosted: Sun Apr 01, 2007 11:13 pm    Post subject: Reply with quote

peterqd wrote:
For the reason Orio mentioned about degrading images, I have never, ever, used a filter in battle. One or two have arrived on lenses I've bought and I've kept them on for protection, but they come off for taking pictures.

So, after reading an article about polarising filters, I was intrigued to find out more and I bought a cheapish Hoya circular pol. filter to try.

I have never seen one like it before. The glass is dark-tinted, like sunglasses - the meter is telling me this makes a difference to the exposure of at least 2 stops. In fact it has two tinted glasses, one static next to the lens and one that is free to rotate. I see no effect when I rotate the outer glass except that some reflected light is (almost) eliminated. I was expecting the rotation to create a gradual reduction in light down to virtually nothing, but that doesn't happen. I also see no difference in colours, like I do with my pol. sunglasses, and that's disappointing because it is what I was hoping for.

I confess I don't understand this filter or know how to use it properly. No instructions came with it. Can anyone kindly give me some pointers?


It sounds as if it is doing what and all it should do. You wont see the effect on sky colour or other surfaces through the viewfinder as the filter will only be cutting the reflective light. A two stop loss through the filter is normal. The way to use it is simply as you have already done. Rotate the filter till you see reflected light eliminated or as best as the filter can manage. if using a lens with rotating front element / filter do the adjustment after you have focused, redo if you change focus. no need for this if you have an internal focusing lens.


PostPosted: Sun Apr 01, 2007 11:41 pm    Post subject: Reply with quote

Thanks Rob, that's helpful. The only lens I have that rotates is the EF-S 18-55 kit lens, and this hasn't been back on the camera since the day I got my first M42 adapter! Smile

The filter is only 49mm dia - I am intending to use it on my CZJ and Tak lenses to see if it will boost the saturation a little bit.


PostPosted: Sun Apr 01, 2007 11:44 pm    Post subject: Reply with quote

peterqd wrote:
Thanks Rob, that's helpful. The only lens I have that rotates is the EF-S 18-55 kit lens, and this hasn't been back on the camera since the day I got my first M42 adapter! Smile


Same here, Laughing

peterqd wrote:

The filter is only 49mm dia - I am intending to use it on my CZJ and Tak lenses to see if it will boost the saturation a little bit.


it will, just keep in mind (as a practical tip - as I'm not versed in the theory) that the more direct sunlight, the more useful. If the daylight is much diffused as in cloudy days, it is almost useless.