[fekish]

Hello,
i saw a video in youtube saying that we should always use a flter for the lens in order to ensure that the glass of the len will always be secured and no scratches will be made on it.

However if we use a filter all the time, it will not change the quality of the photos?

Thanks.

[SpecialK]

Unless you are at the beach with blowing sand or other conditions, there is no real reason for a UV filter. Digital sensors are not affected by UV like film is.

But if you want to use them to make you feel better about your lens, go ahead. Good ones are expensive, though.

Filters make salesmen happy.

[Ira]

Hello,

However if we use a filter all the time, it will not change the quality of the photos?

Yes, it really can. So why put a crappy piece of glass in front of an expensive lens?

A circular polarizing filter is a wonderful thing to use all of the time, but you sure don't HAVE to. It will also reduce your lens speed by at least one stop.

The best protection for your lenses is a good hood. If the camera is slung over your shoulder and it swings as you turn around, you'll only knock it against the hood. Nothing is going to actually hurt the front element of the lens.

[Adam]

If you make the mistake of using a run of the mill filter with any lens, let alone an expensive one, then, as Ira said, your photos might end up looking worse- different colors, haze, as well as loss of sharpness are ale side effects.

I use hoya pro 1d or SMC pentax filters on all my lenses that can't easily be replaced. All other lenses don't have one. My CPL only comes out when there's a really bright sky out. Photoshop allows for most other forms of color-correction, so I usually don't worry about the CPL otherwise.

[Ben_Edict]

"Protective filters" as Ira, SpecialK and Adam wrote are usually not necessary. Any additional glas in front of the lens will degrade the image quality (IQ). A high quality and expensive filter will degrade IQ less but a cheap filter may lead to very visible quality loss.

In my experience a high quality filter's degradation will not be visible in the final image.

BUT all filters will increase the flareing and ghosting, if you shoot into a bright light source (sun or bright lamps in a room), which leads to unwanted more or less pronounced colour specs in the image. There are several threads here with nice examples.

So, try to minimize protective filter use to those situations, where they are really necessary. Sandy and windy environments, near the beach, when the wind may blow salt spray on the lens etc.

Polarizing filters may be useful, when the sun shines as they help to reduce polarized light, thus increasing the saturation of the sky blues or of foliage etc. They are by no means intended for general use, as
– firstly they do not have a good effect under all the different lighting conditions,
– secondly they reduce the amount of available light, which may lead to longer shutter speeds (and thus blurred images) and
– thirdly, as they include two glass plates, and cheaper modells will degrade the image more, than the simple protective filter.
A good polarizer can be a very fine tool, when applicated under the right conditions. (whether it be circular or linear variety is of no practical importance, when used with Pentax DSLRs - there are several threads about the different properties of polarizers, here).

Other filters which are useful under certain shooting conditions are Graduated Neutral Density (ND grad) filters or Neutral Density (ND) filters. But both varieties are not meant for general use.

You will find lots of valuable information in this forum if you do a search for these different kinds of filters.

Ben