# Why purchase filters when you can white balance?



## lespaul (Jul 15, 2011)

Hey everyone, Im a noob here, so be nice please. 

Well, I just purchased a new set of filters (UV, Polarizing, Flourescent) for my new 28mm lense (77mm dia). I know it may sound silly but,  I was thinking - why would do I need to purchase filter (other than for physical protection of my lens) to enhance my pictures. I mean isnt that the purpose of white balancing? 

And furthermore, IF Im shooting in RAW I can always adjust this in post, right?

I hardly ever shoot in RAW, mainly JPG but just had to mention it. I guess if I dont want to spend the time manually adjusting color (even in JPG) I guess that is where the filters may come into play (ie. simply convenience). 

Any feedback is appreciated.


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## Robin Usagani (Jul 15, 2011)

Didnt you have these questions before you bought those filters?


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## 480sparky (Jul 15, 2011)

Since you shoot Jpegs, it will be much more difficult to correct white balance in post if you're way off.  Slightly off will work, but if you shoot at 6000°K in a room full of candles, your correction in post is gonna look like crap.  Shooting in raw, I still doubt you'd get there.

If you're shooting in Auto WB, you'll probably be close enough to make any minor corrections in post.


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## ann (Jul 15, 2011)

the only filter needed, imho would be the cpl. With film, filters corrected for temperature(color flm), with digital your correct you use WB or in Raw corrected as desired after the fact.

Sparky makes a very important point. COrrecting jpeg's is not easy, especially for white balance, better to get it right in camera.


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## Orrin (Jul 15, 2011)

The only one that can be usefull would be the polarizing filter. Generally you cannot duplicate it's effect in post processing.


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## Kerbouchard (Jul 15, 2011)

There are several filters that are important and can't be replicated in post processing...Circular Polarizing, Neutral Density, and Graduated Neutral Density come to mind.

UV filters are worthless, but there are a couple of fun things I could think of doing with a florescent filter...Well, actually only one fun thing, and that would be using the filter and a non-geled flash in different lighting conditions.  You could get some cool effects that would be difficult to reproduce well in post processing.


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## Derrel (Jul 15, 2011)

Some of the diffusion filter effects cannot be replicated in post either...."simulated" or "approximated", usually. But not equalled. Diffusion of the light entering the lens affects how the light is recorded by the sensor or film. Diffusion of highlights into the shadowed areas changes the dynamic range that is presented to the sensor, and the effect cannot be re-created in post processing by simply re-arranging the pixels later, after the fact. The same goes with using gelatin color-correction material at capture time, in order to modify the spectral response of the sensor by modifying the ACTUAL light used to CREATE and to RECORD the image; Iliah Borg often notes that the Nikon D2x sensor requires a 15 c.c. magenta filter added to maximize the color reproduction accuracy of the Nikon D2x when it is used for extremely critical color representation work. Ghe 15 c.c. magenta filter is used to modify that camera's sensor's spectral sensitivity imbalance by modifying the actual light that is used to create and to record the initial image.

How critical and discerning one wishes to approach photography determines one's attitudes about technical matters. Just for chits and giggles, one might want to try using a yellow filter, a red filter, and a green filter over the lens, and then go out and shoot some images using a d-slr, and then come back in and spend a day or two comparing what actually happens when the actual light used to CREATE and to RECORD the images as the light is being focused by the lens, and not well after the fact.

The idea that "everything" can be done later, at the computer, is a fallacy. The light that goes through the LENS is perhaps the most critical aspect of photography. Modifying the light used to create and record the image is what filters do; most Photoshop jockeys fail to be able to grasp this fundamental aspect of photography because they are not actually photographers...


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## Garbz (Jul 16, 2011)

The only filters which really can be replicated perfectly in post processing are the ones which lets certain bands of light through providing the light is within is within the standard red to blue frequencies. 

That means in post processing we can effortlessly emulate a #25A red filter, or a #38A blue filter. But we can not emulate say a #98C infrared filter since we rely on it changing characteristics of the light that hit the lens beyond simply adjusting proportions of red green and blue.


The fluorescent filter falls within the realm of adjusting colours, so it can be matched in post processing. The UV filters don't but then they are a throwback to the film days as camera CCDs aren't very sensitive to UV at all. I use UV only for protection (can't emulate that in post either  ).
The Polariser fundamentally changes the characteristics of the waves of light that hit the sensor. This goes way beyond filters which simply select which bands of light to let through and the effect is very hard to fake too.


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## Overread (Jul 16, 2011)

As an example here are two shots which show what you can get without and with a Polarizer filter; baring in mind the fact that the filter must be turned to apply its effect properly.

Without: 






With:





Polarizers will work on eliminating reflections from non-metalic surfaces.


As for UV filters for protection I always think its important to clarify the kind of protection these offer since some can get the idea that they are some kind of godly shield. A UV filter is think glass infront of your lens, it will protect against mud, sand, water, dust - ie small particles in the air; it also gives you a surface you can quickly wipe clean without worries for scratches on your lens glass.

It won't protect from stones, grit or gravel - these will still shatter the thin UV glass - and it won't really protect against drops either. What it will do in these cases is shatter, risking sending sharp, abrasive glass shards at your front element which can scratch it up. With regard to drops many say that the filter shatters and takes the fall, but they forget that lenses have thick glass anyway and so would have likely survived the drop - however the filter will now be stuck on your filter ring as the mounting often buckles when hit - for droppage the lens hood gives much better protection.

An example is even right here http://www.thephotoforum.com/forum/digital-discussion-q/250211-crushed-glass-lens-any-ideas.html


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## Garbz (Jul 17, 2011)

Overread said:


> It won't protect from stones, grit or gravel - these will still shatter the thin UV glass - and it won't really protect against drops either. What it will do in these cases is shatter, risking sending sharp, abrasive glass shards at your front element which can scratch it up. With regard to drops many say that the filter shatters and takes the fall, but they forget that lenses have thick glass anyway and so would have likely survived the drop - however the filter will now be stuck on your filter ring as the mounting often buckles when hit - for droppage the lens hood gives much better protection.



Protection is not an absolute despite how people here treat it. My bicycle helmet will protect my head for a slight bump but will do nothing against getting hit by a semi doing 100km/h. It's about energy absorption. You still need some amount of force to damage the glass and this force is absorbed by the glass itself and not the front element of the lens. As for the glass shards, well I personally don't feel much either way about this fact. Whether it be a glass shard hitting the lens, or a rock the damage will be done. Certainly I wouldn't worry about a small scratch, they won't show up on photos. 

I've had my share of breakages, and my share of filters jump threads on lenses in the process. They can always be removed with care and so far I have yet to see enough damage caused to the threads that another filter won't screw on again. The same can not be said if the lens were to land on the edge. 


So remember it's a bicycle helmet solution not an airbag in an armored vehicle.


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## KmH (Jul 17, 2011)

lespaul said:


> Why purchase filters when you can white balance?


Because you can't accurately white balance if there is mixed lighting. (mixed lighting = multiple light sources of differing color temperature in the same scene.)


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## Josh66 (Jul 17, 2011)

Overread said:


> Polarizers will work on eliminating reflections from non-metalic surfaces.http://www.thephotoforum.com/forum/digital-discussion-q/250211-crushed-glass-lens-any-ideas.html


Actually, they will work on metallic surfaces too...
(Well, _painted_ metallic surfaces (a car, for example) anyway.  I don't think I've tried it on bare metal, but I don't see why it wouldn't work...)


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## Overread (Jul 17, 2011)

Hmm well paint isn't metal so yeah that makes sense - however as for metallic surfaces when bare metal I've already read that circular polarizers don't work, but then again I've never actually been out to test that on something like sheet metal


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## Josh66 (Jul 17, 2011)

I think a test is in order!  


I have lots of scrap metal laying around here - I think I'll test it out soon and see if it does anything...


Personally, I don't see why bare metal would be any different than a nice and glossy paint job - but I have never actually tested it...  I will some time this week though...


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## 480sparky (Jul 17, 2011)

KmH said:


> Because you can't accurately white balance if there is mixed lighting. (mixed lighting = multiple light sources of differing color temperature in the same scene.)



So let's say you have daylight and incandescent mixed in one shot........... what filter would you use?


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## Josh66 (Jul 17, 2011)

480sparky said:


> KmH said:
> 
> 
> > Because you can't accurately white balance if there is mixed lighting. (mixed lighting = multiple light sources of differing color temperature in the same scene.)
> ...


Yes, very interesting question...  I would like to know as well, since daylight/incandescent is a very common mixed lighting scenario...


(I always thought that a gelled flash was the only solution, but apparently there is some filter that can do it too ... as this is being used as an example of a time when you should buy the filters...)


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