lens filters

[jgredline]

Hi Folks
This is one of many areas that I have problems with..
Are lens filters made to enhance or protect the lens?

[Frog]

They are made to enhance but are frequently used to protect. The one used most often to protect is the uv filter. There's debate over the matter as some say anything in front of the glass will alter the photo. Personally I think a 'quality' uv filter in front of my glass doesn't alter the photo as much as a fingerprint does.
I use a polarizer most.

[Photo-John]

There are clear filters for protecting your lens. And there are colored, shaded, and polarized filters used for altering the quality of your images. The most common filters used for protecting lenses are skylight and UV. They are basically clear with some coatings to help eliminate glare and haze. Most people use protective filters are they're much cheaper than buying a new lens. But some photographers feel that putting a filter in front of the lens defeats the purpose of buying expensive lenses in the first place. Some photojournalists use filters instead of lens caps so they can always have their cameras ready, without having to remove lens caps before shooting. There are many filter strategies. Most people would recommend using a skylight or UV filter to protect your lenses. Replacing a filter is always going to cost less than replacing your lens.

[jgredline]

Thanks for the responses guys..I know that I did spend the money for some real good filters, but I only use them when I am at the beach or hiking where there is wind..I have noticed that a hood lens seems to make more difference..The bigger the better..It also offers some protection as it would be smacked first...

[Skyman]

I have a huge range of filters, uv and skylight protectors, 81a - 81c warming filters (make the shot look like it was taken on a warm sunny day and give skin a tanned look) tungsten light correction filters in varying grades, red and green enhancing filters for landscapes, soft focus and soft spot filters (give the photo a blurred dreamy look) polarising filters (cut down glare and reflections in glass, make the sky look more blue) Poo (yellow green) red, green and yellow filters for black and white however since i went digital i rarely use anything more than a polariser as basically every other effect can be achieved in photoshop and after all isn't it easier to take a good clean image and alter it after if you like it? but then the more i think about it the more i think i should pull out some of the filters. there is a lot to be said about planning an image and appropriate use of filters is certainly about planning. the other thing to look out for is that different lenses will have different filter thread sizes so unless you are using a gelatin filter system like cokin you will either have to get several filters to fit all your lenses or a filter to fit your largest lens and adaptor rings to fit your other lenses. either way you can very very quickly end up with a lot of filters and gadgets.

[deckcadet]

I tend to avoid filters whenever I don't need them artistically. Today's camera lenses and the internal low-pass filter that covers the sensor almost completely eliminate UV, and many digital camera sensors have very little UV sensitivity.

While I can see their value for protection, and have used them for that purpose in *extreme* situations (e.g. shooting outside in a hurricane- it helped a lot), for everyday shooting I avoid them like the plague. In harsh light, they can be a major source of flare and ghosting, and for some lenses can and do have a noticeable effect on optical quality. On a low-end lens, if you use a decent filter you might not really see any effect, though.

For high end lenses, you should never skimp and get a cheap filter, because it will cause problems. The better the lens, the better the filter must be to avoid negative effects.

[freygr]

I tend to avoid filters whenever I don't need them artistically. Today's camera lenses and the internal low-pass filter that covers the sensor almost completely eliminate UV, and many digital camera sensors have very little UV sensitivity.
clip....

You very wrong about the digital camera's sensors. The sensor see into deep IR, that is why there is an IR filter in front of the sensor. The sensor also sees into the UV range also, but not as good as film. They use the same technology of the camera sensors in X-Ray machine sensors, and that is past the UV range. Now the glass in most optics will kill all the short wave UV light, but when you get up in the higher elevations the long UV will add haze and blue to the photos.

[SmartWombat]

They use the same technology of the camera sensors in X-Ray machine sensors

But the X-Ray sensors have a different composition, not all CMOS are created equal.

The important thing is that the CMOS X-Ray sensors usually need to be shielded from the X-Rays.
The imager is a photo-emitter coupled to the sensor with a fibre optic matrix. e.g. the Hamatsu C9321SK-05
Also they're large compared to camera imagers; 50 micro pixels on a 1 megapixel sensor 75cm square ?

Research is going on with direct fabrication, with the scintillator directly on the silicon, but you get damage from the X-Rays and the imager ceases to function after prolonged use with high energy X-Rays.

I know medical sensors after 6 years in a medical imaging unit, but never looked at UV sensitivity.

Wow, this is an excellent paper on the Foveon techonology http://www.alt-vision.com/documentation/5301A-25.pdf

Seems that the performance of other sensors is different though.
Depends on the composition of the bayer filter, but Nikon is reported as UV imaging in the red colour, not the expected blue ?

To get high UV sensitivity you need to get the circuitry off the front of the chip. There's two ways to do that, illuminate it from the backside, or put the sensors in a separate layer and interconnect them to the processing system underneath (tricky micromachining and assembly). Then you need to reduce the amount of silicon in the way, if you're illuminating the sensor from the backside you just make it thinner.

Comparison with nature springs to mind, the human vs octopus eye, where in the human the neural interconnections (the electronics on the CMOS) are in top of the rods and cones and block the light as they exit the eye through the blind spot; in the octopus the layout is reversed, with the neural connections at the rear of the sye so there is no blind spot and nothing obstructing the rods and cones.

[deckcadet]

There is extremely heavy filtration with most digital sensors for UV, freygr. Even with purpose-built quartz UV lenses, sensitivity to UV is many times less than sensitivity to IR and visible light for a great many cameras, especially with CMOS. Certain CCD sensors (nikon's D1 series and D70, to a lesser extent the D200) can have decent to very good UV sensitivity when the low-pass filter in front of the sensor is removed and lenses designed for UV capture (with appropriate filtration to narrow the bandwidth to UV only).

The stock sensors with the standard filtration, however, are designed to eliminate UV, and each successive generation camera manufacturers generally make it even less sensitive. CMOS sensors additionally can have noticeable drop-offs in sensitivity in the middle of the UV band. Even then, the sensors are so much more sensitive to IR than they are to UV that IR contamination is much more of a consideration, imho, than UV contamination for visible light photography. This is why true UV photography requires often extremely expensive filters (such as the Schott UG-11x filter if memory serves, there may be an updated version out already) to provide high levels of UV bandpass while blocking visible light and particularly IR.

The peak of sensitivity was really the original Nikon D1 series, in particular the original D1 if memory serves, for UV. I actually own one and I've stripped out the internal filtration (major disassembly required) to obtain the necessary UV sensitivity. I also use special lenses that transmit UV for those shots.

[jgredline]

Oh i am so confused..LOL

[mwfanelli2]

Oh i am so confused..LOL

As well you should be!

OK, here's the quick and dirty. You do not have to worry about UV or infrared light ruining your photos. The camera has taken all of that into account. On digital cameras (and with film produced in the last 20 years or so), a UV filter only serves as "protection."

Some people swear by protection, others do not. I have not used full-time protective UV filters in over 35 years of photography and have never had a problem. Others dig up stories of "my filter saved my lens!" It really depends upon how paranoid you are. If you do decide to use a full-time UV filter for protection, spend the bucks on a top line multi-coated one from B+W, Heliopan, or Hoya. Do NOT use two filters at the same time. The filter will be the weakest link in your lens.

The only filter you really need for digital is a polarizer (never for full-time use). No software can duplicate it. An ND filter might be useful to slow down shutter speeds. A grad ND filter can be duplicated better in software but some people still like using the filter. Color correction filters are not required for digital.

Hope that helps.

[another view]

OK, here's the quick and dirty.

That's my opinion on this too. I do almost always use the lens hood designed specifically for the lens, and about the only time I don't use a hood is when I'm using a polarizer (so I can turn the ring). If I think glare may be an issue, I'll set the polarizer then either put on the lens hood or shield the sun with my hand (being sure it's not in the frame).

I did damage a lens one time where it would have been saved by a filter. That was my own carelessness, and the cost of the damage was $100 (used value of the lens versus price I sold it for as parts on ebay). $100 wouldn't outfit all of my lenses with good UV filters. I have one, and use it in conditions where the lens is very likely to get waterspots or dirt on it.

DSLR's right out of the box are very, very good. Don't worry about UV and IR in 99.9% of situations. Digital is different than film, but I've never had a problem with UV or IR with either film or digital.

[fx101]

I use a filter so I don't have to remove a lens cap (as has been stated) when shooting an abrupt subject. A UV filter in that case. The only two filters you will probably ever need in the digital world are:

A high quality circular polarizer

An ND filter (for sunsets a graduated one might be more useful)
or
For super-wide angle lenses, Wratten 2 ND gel filters. (wrattens can actually be better in quality).

[jgredline]

As well you should be!

OK, here's the quick and dirty. You do not have to worry about UV or infrared light ruining your photos. The camera has taken all of that into account. On digital cameras (and with film produced in the last 20 years or so), a UV filter only serves as "protection."

Some people swear by protection, others do not. I have not used full-time protective UV filters in over 35 years of photography and have never had a problem. Others dig up stories of "my filter saved my lens!" It really depends upon how paranoid you are. If you do decide to use a full-time UV filter for protection, spend the bucks on a top line multi-coated one from B+W, Heliopan, or Hoya. Do NOT use two filters at the same time. The filter will be the weakest link in your lens.

The only filter you really need for digital is a polarizer (never for full-time use). No software can duplicate it. An ND filter might be useful to slow down shutter speeds. A grad ND filter can be duplicated better in software but some people still like using the filter. Color correction filters are not required for digital.

Hope that helps.

Thank you..This is what I wanted to know..I do not know about x ray machines or sensors or anything like that, but I really appreciate ''all'' the people who took the time to write...That means allot to me!!!!

Now if I may ask? What is the function of a polarizer?

[another view]

Here are some basics on a polarizer from Hoya. I happen to have one of their multi-coated polarizers and it's very good.

Polarizers have maximum effect at 90 degrees from the light source (usually the sun, since it's so dominant outside). When the angle gets closer, the maximum effect is less. They will cost about 1 - 2 stops of light depending on how much effect that you can get so only use them when needed - some people love the effect and want to keep them on the lens all the time but it doesn't work that way. They won't do much of anything on an overcast day because the light is coming from everywhere.

Maximum effect isn't always a good thing. Over-polarized shots can look fake; like processing too much in Photoshop. It's usually more of a problem at high elevations, but can happen anywhere. Just like all of photography, getting the finished shot that you want is the goal.

[jgredline]

Here are some basics on a polarizer from Hoya. I happen to have one of their multi-coated polarizers and it's very good.

Polarizers have maximum effect at 90 degrees from the light source (usually the sun, since it's so dominant outside). When the angle gets closer, the maximum effect is less. They will cost about 1 - 2 stops of light depending on how much effect that you can get so only use them when needed - some people love the effect and want to keep them on the lens all the time but it doesn't work that way. They won't do much of anything on an overcast day because the light is coming from everywhere.

Maximum effect isn't always a good thing. Over-polarized shots can look fake; like processing too much in Photoshop. It's usually more of a problem at high elevations, but can happen anywhere. Just like all of photography, getting the finished shot that you want is the goal.

Great, Thanks..Since I like to shoot the majority of the time during daylight hours when the sun is its brightest, would it be fair to say that I would benefit from a polarizer?

[another view]

Yes, you probably would find it handy. Mid-day sun isn't always the best light for photography, and another good technique you might want to work on is fill flash. Basically, that's using a flash to "fill in" the shadows and make things look more natural. When a flash is used for fill, it's usually toned down a little bit (maybe 1 or 2 stops less) than full flash that you might use indoors.

You can use both together - for example, if you're shooting a portrait the polarizer would still have an effect on the sky but the fill flash would make the subject look better. Some cameras will make this easier than others though - it could take a lot of manual compensation to get everything where you want it.

[mwfanelli2]

Thank you..This is what I wanted to know..I do not know about x ray machines or sensors or anything like that, but I really appreciate ''all'' the people who took the time to write...That means allot to me!!!!

Now if I may ask? What is the function of a polarizer?

A lot of people assume that all a polarizer does is make the sky bluer. That is not the case. Most reflections, including "glare" off the sky, is polarized light. The polarizer blocks this polarized glare. This allows you, for example, to get rid of reflections on glass or the glare reflecting off of water. It only works when there is polarized light, usually when the sun is at a 90-degree angle to the direction you are shooting. It can occur at other times as well, such as the light reflecting off of water at a 30-degree (40 degree?) angle.

No software can do the work of a polarizer.

[jgredline]

A lot of people assume that all a polarizer does is make the sky bluer. That is not the case. Most reflections, including "glare" off the sky, is polarized light. The polarizer blocks this polarized glare. This allows you, for example, to get rid of reflections on glass or the glare reflecting off of water. It only works when there is polarized light, usually when the sun is at a 90-degree angle to the direction you are shooting. It can occur at other times as well, such as the light reflecting off of water at a 30-degree (40 degree?) angle.

No software can do the work of a polarizer.

Oh my gosh..You hit my problem right on the head, thank you!!
Often times ''now'' I would run into a good shot but It would be directly into the sun so I would get up as much as I could, but still there would be flaring and so now I avoid all those type of shots all together..I will be heading to samys camera today to buy a couple of polarizers.
Thanks a bunch..

[another view]

Actually a polarizer won't help with that. It won't get rid of lens flare, and if the sun is in the frame it will still be totally blown out. Also, using any filter shooting into the sun (sunrise/set included) could cause problems with light bouncing around between the front element of the lens and the back side of the filter.

I have shot into the sun and did a fair amount of it with slide film, but it doesn't work as well with digital. Sensors don't like it much, either.

[jgredline]

Actually a polarizer won't help with that. It won't get rid of lens flare, and if the sun is in the frame it will still be totally blown out. Also, using any filter shooting into the sun (sunrise/set included) could cause problems with light bouncing around between the front element of the lens and the back side of the filter.

I have shot into the sun and did a fair amount of it with slide film, but it doesn't work as well with digital. Sensors don't like it much, either.

Oh, ok....Let me find a pick and post it here to put it in context..
Thanks all..