Does stacking more lens filters decrease overall image quality?

Question

As commented by t3mujin in another question:

Stacking filters will decrease image quality, as it's another piece of glass light has to go through before reaching the sensor.

I was wondering whether this is true, or better yet, how radical the quality decrease really is?

I was thinking about using UV filter on my lens and on that, stacked a polarizer. This combination of filters sounded to me like a great idea on how to shoot the nature, but after I read the aforementioned, I'm really wondering whether I might be wrong.

What would be the best option for this situation?

Answer 1

Anytime you add something in the optical path you will lose quality. The quality you will lose depends on the filter quality, filter type and lighting conditions.

Most filters are extremely susceptible to flare because they add a flat reflective surface and can take a great image and make it completely unusable. That does not mean you should never use a filter or even more than one, but you should do so for a valid reason knowing the sacrifice you are making at the same time.

Polarizers have specific usage and an effect which cannot be simulated by software, so use them to cut-down reflection, increase saturation in the sky, etc. No need to add it over another filter that essentially does nothing.

UV filters have a use too but are rarely actually needed. They are usually recommended at high-altitude but AWB or custom white-balance takes care of that. Since they are cheap and do not cut-down light by much you can use them to protect your lens when it is in eminent danger such as near salt-water and flying sand.

Against knocks, a lens hood is much more effective protection and may even increase image quality by reducing flare from stray light.

Answer 2

A new blog post about stacking filters has just came out at LensRentals.com, and the findings are:

• Filter quality really matters: good filters have minimal impact on image quality, while cheap/bad ones degrade the image a lot more
• Stacking 50 UV filters on a lens is really too much, especially if you include some lower-quality ones

Answer 3

"What would be the best option for this situation?"

For myself, I am happiest using only the minimum number of filters that I find necessary for any given photo. I use a UV/Haze filter to keep dirt off of the front element, but remove it when shooting at night or when I want maximum contrast and the least amount of flare. I remove the Haze filter and use a Circular Polarizing filter when I want to darken the sky or see through a reflective surface. I do not use both a Haze and Circular Polarizing filters at the same time.

I do not think that I would be happy trying to use two polarizing filters as a ND filter would produce photos that I would be happy with, it is most likely not something I will try anytime in the near future.

But the amount that filters will enhance or degrade an image is subjective, you may really like the affects you get by adding more than one filter at a time, maybe to produce a grunge look, or a toy camera look, or just something new you have not seen before. There are no rules here, go crazy.

Answer 4

Yes stacking filters will decrease image quality:

If you use enough of them!

photos (c) TastyPrawn

Answer 5

To summarise I'd say in my opinion the loss of image quality is normally tiny unless your filter is particularly poor quality. Normally it's the loss of light that is a problem.

In detail:

I've always worked on the basis that a UV filter cuts down 5% of the light although now I try and find a source to that, I can't.

Personally I avoid UV filters at all times unless I am high in the mountains or there is a lot of dust, sand or seawater around.

I would avoid stacking filters if you can help it - there are combined UV polarisers around (you can get a warm up polariser too.) I stacked two polarisers a while back - to try and make a variable ND filter - and the quality loss was horrific. Still not sure exactly why, though one of the filters was very cheap. It worked OK on its own though.

(Interestingly the Canon 500mm f/4 lens which I use quite a bit comes with a drop in filter that is clear glass - when you're not using a UV or polariser in there, you're supposed to use the clear filter.)

Answer 6

Yes. Light will bounce back and forth between your filters, and leave haze and flare on your photos.

If you must stack filters, try not to shoot towards any strong light sources.

Personally I always use UV filters to protect my lens. And when shooting towards the sun, the degrading on image quality is visible.

Answer 7

A 17-element lens has 34-air-glass interfaces. That is 34 surfaces for light to bounce around and reduce image quality. Since "anytime you add something in the optical path you will lose quality", removing elements from a lens should improve image quality. Each element I remove from the lens should improve quality by removing two air-glass interfaces. Remove one element, and it becomes a 16-element lens with only 32-air-glass interfaces and the improved image quality to show for it. Remove another, and it's a 15-element lens with even better image quality.

Imagine the image quality when it is down to a 1-element lens. Then finally, the holy grail of image quality, which one cannot even imagine, a 0-element lens! It is so amazing, your mind simply cannot comprehend it. You will be in denial that this is the pinnacle of image quality. Here is a photo taken with a 0-element "lens":

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The best way to determine the effect filters will have on your lenses is to take your own test shots.

After reading Good Times with Bad Filters, I decided to try the stacked filter experiment myself. I took test shots without UV filter and with five stacked multi-coated UV filters plus an uncoated filter for good measure. The filters looked clean enough, so I did not clean them.

Camera sharpness and noise reduction were set to default (0). Camera was set to Full Auto, so images were underexposed with poor white balance. I compensated with some mild post-processing to increase exposure and correct white balance. I did not increase contrast or apply additional sharpening.

Again, take your own test shots with your own lenses and filters to see the effects and to satisfy yourself that your shots will meet your own personal quality standards.