[Docrwm]

We've gotten a little off the OP's main topic. Other than for Astrophotography of the Galactic Core (well wide field anyway) are their legitimate optical reasons for using a UV filter on Digital SLRs? The general consensus is no, there are no legitimate uses specifically for UV protection on modern cameras. Are there other filters that continue to have a legitimate use today? Yes, CPL and ND filters can produce effects that are either impossible in post-processing or very difficult an/or time consuming that are relatively easy and quick with a filter.

On the issue of protection filters - YMMV is the best answer. On a clear day with no blowing debris and no real chance of contact with the front element of my lens I do not use protection filters. On days when wind is pushing sand or other debris, or I'm in a situation where it is more likely that something may come into contact with my front element I do use a protection filter on most lenses - particularly on lenses with huge front elements. Filters are relatively easy to take off and put on, so if I have it with me its available for use but if I don't all I can do is put the lens cap on and then I can't take any photo. Yes, a hood is a huge plus and I use them religiously because they nearly always improve the photo. They also protect the lens to a degree. However, blowing sand is the perfect example of where the hood helps but not enough.

In my home, inside a gym, or frankly inside nearly anywhere - no filter. Outdoors with any risk of damage to the front element - probably have that filter with me. I do recommend looking at Lenstip's reviews. Maker is NOT the main determinant of quality in filters. There were really bad Hoya filters that cost a good bit on the list. When I do use a filter I try to get the best that I can optically to minimize its negatives.

That's my take on it.

[Hamiltom]

So take the filter off for those shots and put it back on to protect the lens later.


---------- Post added 01-12-15 at 07:51 ----------





What lens hood do you recommend in this situation? Is there a nice and compact one that has a force field to deflect FOD before it scratches the front element?





obin

If you are taking shots in the midst of flying debris, you might consider a blind or shelter.

Actually the shot posted would have been drastically improved with a Circular polariser, not a UV filter.

[Obin Robinson]

We've gotten a little off the OP's main topic. Other than for Astrophotography of the Galactic Core (well wide field anyway) are their legitimate optical reasons for using a UV filter on Digital SLRs? The general consensus is no, there are no legitimate uses specifically for UV protection on modern cameras. Are there other filters that continue to have a legitimate use today? Yes, CPL and ND filters can produce effects that are either impossible in post-processing or very difficult an/or time consuming that are relatively easy and quick with a filter.



That's my take on it.

UV filters are used in astrophotography to cut down on the purplish halo or fringe which will ruin an otherwise good astro photo. Digital cameras are sensitive to a wider spectrum of light than the human eyes are. This leads to an unnatural looking astro photo where the stars are bluish but when you look through the eyepiece they are plain white. The UV light is slightly out of focus compared to the rest of the spectrum. A good UV filter can work wonders for the millions of us who can't afford or don't own the Ultra-Achromatic-Takumar which focuses all wavelengths at exactly the same distance from the front element. Astro photographers push gear and filters further than any other photographer. You may leave a DSLR shutter open for 10 minutes or longer for several hundred times just to photograph one object. In the process of photographing that object you may swap out filters several times and then have to refocus the camera because the wavelength you are capturing is now out of focus compared to the last one.


You may wonder "okay that's good for astrophotography but what can a UV filter do in daytime?" Take a look at this thread on CN and scroll down to the post by skyguy where he says

Here's a shot of a barn cupola and power wires taken with (right image)and without (left image) the Baader 495 Longpass using a 70mm f/5.7 achromatic refractor. They are both raw and untouched, except the 495 Longpass filter image was color corrected in Photoshop.

ST80 with Baader 495 Longpass filter - Refractors - Cloudy Nights


If you can't see the difference and still refuse to believe that UV filters are helpful then I give up. It just means that you're being stubborn because the difference is readily obvious. I have several refractors I use for astrophotography: an ST-80, an ED-80, and a Burgess 127mm. When I use the UV filters there is a humungous difference in the quality of the image. I have several different filters I use and if they were for daylight photography they would be considered "UV" or "UV-IR cut" filters. Not only do the images show a difference but the histograms agree with what my eyes are seeing as well.

obin

---------- Post added 01-12-15 at 08:23 ----------

If you are taking shots in the midst of flying debris, you might consider a blind or shelter.

Actually the shot posted would have been drastically improved with a Circular polariser, not a UV filter.

You propose that an aircraft mechanic brings a blind or shelter onto the ramp or flight deck? Umm. That's not going to happen. That shot was just a quick example. I've used a circular polarizer as well on the aircraft carrier however it got ruined by jet fuel and hydraulic fluid.

[Docrwm]

UV filters are used in astrophotography to cut down on the purplish halo or fringe which will ruin an otherwise good astro photo. Digital cameras are sensitive to a wider spectrum of light than the human eyes are. This leads to an unnatural looking astro photo where the stars are bluish but when you look through the eyepiece they are plain white. The UV light is slightly out of focus compared to the rest of the spectrum. A good UV filter can work wonders for the millions of us who can't afford or don't own the Ultra-Achromatic-Takumar which focuses all wavelengths at exactly the same distance from the front element. Astro photographers push gear and filters further than any other photographer. You may leave a DSLR shutter open for 10 minutes or longer for several hundred times just to photograph one object. In the process of photographing that object you may swap out filters several times and then have to refocus the camera because the wavelength you are capturing is now out of focus compared to the last one.


You may wonder "okay that's good for astrophotography but what can a UV filter do in daytime?" Take a look at this thread on CN and scroll down to the post by skyguy where he says

ST80 with Baader 495 Longpass filter - Refractors - Cloudy Nights


If you can't see the difference and still refuse to believe that UV filters are helpful then I give up. It just means that you're being stubborn because the difference is readily obvious. I have several refractors I use for astrophotography: an ST-80, an ED-80, and a Burgess 127mm. When I use the UV filters there is a humungous difference in the quality of the image. I have several different filters I use and if they were for daylight photography they would be considered "UV" or "UV-IR cut" filters. Not only do the images show a difference but the histograms agree with what my eyes are seeing as well.

obin


You propose that an aircraft mechanic brings a blind or shelter onto the ramp or flight deck? Umm. That's not going to happen. That shot was just a quick example. I've used a circular polarizer as well on the aircraft carrier however it got ruined by jet fuel and hydraulic fluid.

[Hamiltom]

UV filters are used in astrophotography to cut down on the purplish halo or fringe which will ruin an otherwise good astro photo. Digital cameras are sensitive to a wider spectrum of light than the human eyes are. This leads to an unnatural looking astro photo where the stars are bluish but when you look through the eyepiece they are plain white. The UV light is slightly out of focus compared to the rest of the spectrum. A good UV filter can work wonders for the millions of us who can't afford or don't own the Ultra-Achromatic-Takumar which focuses all wavelengths at exactly the same distance from the front element. Astro photographers push gear and filters further than any other photographer. You may leave a DSLR shutter open for 10 minutes or longer for several hundred times just to photograph one object. In the process of photographing that object you may swap out filters several times and then have to refocus the camera because the wavelength you are capturing is now out of focus compared to the last one.


You may wonder "okay that's good for astrophotography but what can a UV filter do in daytime?" Take a look at this thread on CN and scroll down to the post by skyguy where he says

ST80 with Baader 495 Longpass filter - Refractors - Cloudy Nights


If you can't see the difference and still refuse to believe that UV filters are helpful then I give up. It just means that you're being stubborn because the difference is readily obvious. I have several refractors I use for astrophotography: an ST-80, an ED-80, and a Burgess 127mm. When I use the UV filters there is a humungous difference in the quality of the image. I have several different filters I use and if they were for daylight photography they would be considered "UV" or "UV-IR cut" filters. Not only do the images show a difference but the histograms agree with what my eyes are seeing as well.

obin

---------- Post added 01-12-15 at 08:23 ----------





You propose that an aircraft mechanic brings a blind or shelter onto the ramp or flight deck? Umm. That's not going to happen. That shot was just a quick example. I've used a circular polarizer as well on the aircraft carrier however it got ruined by jet fuel and hydraulic fluid.

I think the point that can be made here is that circumstances, available choice of optics, can alter the decision on whether or not to use a filter.

The best choice is the one that improves the end result. UV filters and yellow filters, like the Baader 495, can increase the apparent contrast and reduce CA in less expensive optics, but most modern photographic lenses are quite good in this respect.

Note the example images are from a 80mm f/4 achromatic refractor, not a typical camera lens and the filter is on the eyepiece not the objective lens.

[Obin Robinson]

The best choice is the one that improves the end result. UV filters and yellow filters, like the Baader 495, can increase the apparent contrast and reduce CA in less expensive optics, but most modern photographic lenses are quite good in this respect.

Note the example images are from a 80mm f/4 achromatic refractor, not a typical camera lens and the filter is on the eyepiece not the objective lens.

I've pushed my camera lenses pretty hard when doing astrophotography. Take a look at this post:


Canon EOS EF 300mm f/2.8 L USM IS Astrophotography Tests

I realize that these camera lenses were designed for daytime terrestrial photography and not astrophotography of point sources across the entire field. Even using ED and Fluorite glasses I would not expect the color correction to be perfect on a point source, especially given the speed of the optical system in these super telephotos.



However, I have considerable experience with these types of lenses for astronomical imaging on film, and haven't seen these kinds of gross aberrations before. Initially I thought the halos might have something to do with the low pass filter in front of the CMOS sensor in the camera, but I don't see them on shots taken with the telescope. And that also would not explain why the halos are off center. That is what I really don't understand.
Quite honestly, I don't know what is going on. I'm just shocked. I don't know if it's the IS elements possibly being tilted slightly or what.

The fact that these aberrations were not present in the images taken through the apochromatic refractor indicate that the problem is not in the camera or sensor.


Update 3/3/2005


Examples of the stellar aberrations seen here in the Canon 300mm f/2.8 L USM IS and Canon 400mm f/2.8 L USM IS lenses were sent to the Canon lens development group in Japan. According to a reply received by Rudy Winston, one of the top technical support people at Canon USA, the Canon lens development group feels that the lenses are performing within specifications, and that the images show results they'd expect in shooting this type of subject with those lenses. They don't feel there's anything wrong with these lenses that the service department would be able to fix.


...


It appears that the high resolution and linear data-recording capabilities of these digital cameras are now able to detect lens aberrations that were previously hidden when the lenses were used with film.
In my opinion, these lenses are not usable for high-quality long-exposure deep-sky astrophotography when used wide open unless the photographer is willing to clip a significant amount of highlight detail in the stars.

Lens aberrations that you won't notice in daylight suddenly become obvious with 4,000 seconds of integration time. "Pixel peeping" is a necessity in order to properly collimate optics as well as achieve proper focus. Even good camera glass will show fringes and chromatic aberration. Even good camera glass will have the edges of the image showing oblong stars with colors being shifted at the fringes. The example above with the ST-80 shows that what is being observed visually is also what is being captured through the camera. It helps with a short tube achromat but it also helps with a semi-apo and apo refractor as well. There is plenty of documentation on the difference that the "minus violet" filters make with any sort of imaging system which uses lenses. Unless you are using fluorite or some other sort of ultra low dispersion lens or coating there is going to be some chromatic aberration. The only way to fix this is to do stacks of narrow band images but that is completely impractical for daylight photography. For those of us who don't have thousands of dollars in loose change to toss at fluorite lenses the next best bet is to at least remove the common offending wavelengths and then correct the colors later.


obin

[Suleeto]

When my new prime arrives in the mail, I'll be taking shots with and without the cheap filter, indoors and out, sun and overcast. We shall se... but what little may be lost (or may not be!) seems worth the protection.

What I can say is yesterday I took some shots with both my M 50mm F2 and the 18-55 WR, with and without filters, outside on an overcast day, and then proofed them on my big monitor and nothing seemed notably different. Now these aren't "expensive" lenses by any means, but these UV/glare filters are simply "on there" with no apparent detriment. And of course, the benefits of "protection". And honestly, I'm not a professional. If I can help it, I'd prefer not to replace anything, or regard some lenses as "throw away" and treat them carelessly. My camera body is worth less than some of the lenses some of you shoot with. Yet I can take an old M and my K-50 and a cheap UV/glare filter and take just as amazing a shot with the right opportunity.

I will look into CPL and ND filters. Now, would there be any detriment to running a filter on a filter? Say, an ND on a UV? I'm trying to determine if there is any need to remove the "usual" filters I have on, not that they are hard to remove... of course they aren't.

[Docrwm]

When my new prime arrives in the mail, I'll be taking shots with and without the cheap filter, indoors and out, sun and overcast. We shall se... but what little may be lost (or may not be!) seems worth the protection.

What I can say is yesterday I took some shots with both my M 50mm F2 and the 18-55 WR, with and without filters, outside on an overcast day, and then proofed them on my big monitor and nothing seemed notably different. Now these aren't "expensive" lenses by any means, but these UV/glare filters are simply "on there" with no apparent detriment. And of course, the benefits of "protection". And honestly, I'm not a professional. If I can help it, I'd prefer not to replace anything, or regard some lenses as "throw away" and treat them carelessly. My camera body is worth less than some of the lenses some of you shoot with. Yet I can take an old M and my K-50 and a cheap UV/glare filter and take just as amazing a shot with the right opportunity.

I will look into CPL and ND filters. Now, would there be any detriment to running a filter on a filter? Say, an ND on a UV? I'm trying to determine if there is any need to remove the "usual" filters I have on, not that they are hard to remove... of course they aren't.

Yes, you get at least additive and sometimes multiplication of the aberrations by adding filter on filter. There was a great article at one of the lens rental outfits on stacking filters and how bad the effects are but I can't seem to find the reference right this minute.

[abmj]

Stacking dissimilar filters is a bad idea. Too much chance of creating a reflection chamber between them. The only time I will stack filters is with multiple NDs to create a factor I don't have in a single. For example, a +2 added to a +3 creates a +5, which I may not have. Otherwise, when I put on, say, a CPL, I take off the clear protection filter, etc. Adding one layer of glass in front of my lens I don't worry too much about. Adding two or more, I do worry about.

[Docrwm]

Stacking dissimilar filters is a bad idea. Too much chance of creating a reflection chamber between them. The only time I will stack filters is with multiple NDs to create a factor I don't have in a single. For example, a +2 added to a +3 creates a +5, which I may not have. Otherwise, when I put on, say, a CPL, I take off the clear protection filter, etc. Adding one layer of glass in front of my lens I don't worry too much about. Adding two or more, I do worry about.

Even there you add the distortions of each to the ultimate image. I understand that it may be necessary and have to be dealt with but even similar types of filters add their distortions cumulatively when stacked.

I found one of the articles about stacking filters that I was looking for, I know that they went to extremes but their conclusions and point are none-the-less sound IMHO.

http://www.lensrentals.com/blog/2011/06/good-times-with-bad-filters

[promacjoe]

Certain camera lens do not like one filter, much less two. You get corner cropping. as stated above, multiple filters Is a bad idea for any lens. although in film cameras, there were certain combinations that you could use to get a desired effect, But these were rare. generally it was a bad idea. For digital cameras, Other than ND and polarizers, any special effect that you can get by stacking filters, can be done in postprocessing.

[ROBEFFY]

Certain camera lens do not like one filter, much less two. You get corner cropping. as stated above, multiple filters Is a bad idea for any lens. although in film cameras, there were certain combinations that you could use to get a desired effect, But these were rare. generally it was a bad idea. For digital cameras, Other than ND and polarizers, any special effect that you can get by stacking filters, can be done in postprocessing.

I agree, seems like CPL and ND can be useful, and postprocessing can likely handle the rest.
I put a clear filter on everything, as I walk through bush, kayak, hike often with the camera. Usually I just leave the filters on, however, I will try sample shots without when I think of it.

[bm777]

So am I overdoing it by having a UV and a polarizer on all my lenses as standard? Was looking for this topic for a long time!
thanks
bosco

[abmj]

So am I overdoing it by having a UV and a polarizer on all my lenses as standard? Was looking for this topic for a long time!
thanks
bosco

As a general rule, polarizing filters should only be put on when they are called for. They only show the effect when shooting "across" the light and not "with or against" the light. If not careful, you can get some funny effects, particularly with wide angles. And you will lose 1 to 1.5 stops of light just by putting on a polarizer. Best to reserve it for when you need it.

[bm777]

Thanks Jim...However leave the UV on at all times...