October 30, 2014, 09:10:34 AM

Author Topic: Image quality with or without filters  (Read 2513 times)


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Re: Image quality with or without filters
« Reply #15 on: August 20, 2014, 03:52:19 PM »
The only time I have noticed the difference is when photographing through glass using my 50/2.5 macro to take photos obliquely through a London bus window. There's always an extra chance to pick up extra reflections and artifacts with extra glass ahead of the front element. A hood may have helped, but the lens doesn't otherwise need one because the front element is so deeply recessed. Apart from ND and orange filters for b&w film, I haven't used a filter on that lens since.

On my only weather sealed lens, I soon bought a Hoya HD protect (not UV) filter permanently in place. I can't fault the IQ with or without filter.
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Re: Image quality with or without filters
« Reply #15 on: August 20, 2014, 03:52:19 PM »


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Re: Image quality with or without filters
« Reply #16 on: August 20, 2014, 07:35:51 PM »


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Re: Image quality with or without filters
« Reply #17 on: August 20, 2014, 07:45:35 PM »
Here is a great test; http://www.lenstip.com/113.1-article-UV_filters_test.html
They did some thorough testing, but I'll repost some caveats about interpreting their results in the context of use on a dSLR:

Just be aware of how LensTip's scoring is derived.  One factor (25% of the scoring) is how effective the filter is at blocking UV light, and that is irrelevant for dSLR users.  In fact, in one sense better UV blocking is worse, because some of the deep blue light is also lost.

Hoya, Zeiss, and B+W all publish their transmission curves. No filter has a perfectly vertical cutoff on a transmission curve - most good commercial multicoated filters that 'block' wavelengths ramp from ~0% transmission to their max of >99% over a 25-125 nm range (although some of the longpass and bandpass filters I use in microscopy are close to vertical, with a slope covering <5 nm - and they come with a price tag commensurate with that performance). 

The Zeiss has the steepest slope of the three, ramping up over the 410-435 nm range (it's cutting out some blue light, which is considered to start at 400 nm). The Hoya has the least steep slope, running from 350-460 nm or so, meaning its passing some UV in the 350-399 nm range, and blocking a bit of blue light as well.  The B+W is intermediate, ramping up from 360-430 nm, but at 400nm (the start of the visible range) the B+W UV transmission is >90%, and the sensitivity of the CFA blue channel on the sensor is very low below 420nm anyway.

Of course, while that might be good to know if you're shooting film, none of that matters if you've got a dSLR.  The dSLR's sensor is insensitive to UV light, so there's no difference between a UV filter (be it the 410 nm Zeiss or the 360 nm B+W) and a clear filter that fully passes the long end of the UV spectrum.  I have empirically tested my 7D and 5DII for UV sensitivity with calibrated UV/Vis light sources and some of those precise bandpass filters mentioned above (running a lab that has such equipment comes in handy sometimes) - there's no need for a UV filter.  I do use UV filters for protection (B+W MRC or Nano), instead of clear - but that's only because every time I've needed to buy one, the UV version was cheaper than the clear one (although that's not the case with all brands or in all geographies).

For the Lenstip tests, I recommend looking at the test results, not the summary table.  For example, compare the top scoring Hoya with the 3rd place B+W - the Hoya scored 90% (36/40), the B+W scored 83% (33/40).  But, when you look at the subscores which they provide that sum to a possible 40 pts, you see that B+W loses 1 pt for visible transmission, 1 pt for flare, and 5 pts for UV transmission.  The Hoya loses 2 pts for visible transmission, 2 pts for flare, and gets 10/10 for UV transmission.  But for a dSLR user, UV transmission is irrelevant...meaning that for a dSLR user, the B+W is the better filter according to Lenstip's testing, since it's better on both visible light transmission and flare.
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Re: Image quality with or without filters
« Reply #18 on: August 21, 2014, 12:33:57 AM »
If your a pixel peeper you can tell a difference when using UV filters and I did a quick simple test a little while back to show that under close inspection you can tell the difference between shots when you use one vs. not using one.


But I also proved that under NORMAL viewing of images on the PC, you cannot really tell them apart. Of course a few tried to say that I needed to provide the RAW files so you can pixel peep... etc... but that wasn't the point of it. When you look at an image normally, you cannot really tell them apart.

Even a cheap filer will help protect your glass against minor accidents and scratches. It's cheap insurance and you won't reduce the image quality by any noticeable amount. :)

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Re: Image quality with or without filters
« Reply #19 on: August 21, 2014, 12:41:23 AM »
Agree with those that say a good quality one has no adverse effect apart from flare, but as I shoot into the light a lot I don't use them, unless I'm in a really aggressive environment. The multi coatings of these lenses are really tough.

+1,  good quality filters have minimum effect on picture quality. I agree that shooting indoors can save you from using/requiring the extra protection of filters, although I prefer keeping them on, not only for extra protection but also are easier to clean.
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Re: Image quality with or without filters
« Reply #19 on: August 21, 2014, 12:41:23 AM »