Teach me about: filters

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Migroo

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Chris
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Hi guys

Today was the first time I realised I might need more than the basic UV filter.

I was taking a shot of some moving water and had the following settings - ISO 100, 2 seconds, F22. I couldn't lower the ISO or increase the F-stop any more, and I wanted a longer shutter speed.

Is there a filter available to reduce the light reaching the sensor?

What others should I look into getting?
 
Have a look at neutral density filters. I don't own one but I believe they are used to slow down the shutter speed to get that creamy water effect on waterfalls etc.
 
Thats great thanks ziggy.

With filters do you get what you pay for, and is there a sensible starting point?

None of my lenses are particularly good - the best I have is a EF 50mm F1.4 prime. Is it OK to spend £20 on a filter for this sort of lens, or do I need to spend more to make sure I'm not adversely affecting the image quality?
 
Have a look into the Cokin P filter holder, an adapter ring for your lenses (couple of quid on Ebay from Hong Kong) and a set of HiTech 85mm ND filters to fit the holder (generally considered to be more neutral than the Cokin ND filters, and less expensive than Lee etc). The set has 3 ND filters of varying strengths, ND 0.3 (1 stop), 0.6 (2 stops) and 0.9 (3 stops) and can be stacked in the holder. With the right adapter rings, you could use this set with all your lenses with filter size up to 80mm (I think).

For very long exposures you'll need a very strong ND filter, often referred to as a "big stopper". These can be expensive but you can improvise using an adapted welding glass. Have a look around, there's a thread on it somewhere.

Edit: Also, a circular polarizer will add nearly 2 stops, which would be enough to turn your 2 second shutter speed into nearly 8.
 
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Hi ZoneV

Thanks, that filter holder sounds ideal.

Re: welding glass -yes I've seen the thread. Definately need to try it!
 
Just to say that if you are stopping down to f22, you will be degrading your image quality due to diffraction so use ND filters to avoid having to stop down so far!

Also check out Fader ND's - they can be very useful tools since you can have up to 8 or 9 stop in one variable filter.
 
Hi travellingcello - thats interesting, I had no idea! What F stop should I aim to stay above to avoid diffraction?
 
travellingcello said:
Just to say that if you are stopping down to f22, you will be degrading your image quality due to diffraction so use ND filters to avoid having to stop down so far!
Click to expand...

But surely putting more glass (the ND filter) in front of the lens will degrade image quality also? Which is likely to have more effect though, stopping down to f22 or adding an ND filter? :shrug:

I would say be wary of the variable density filters also, I think there are issues when they are used with wide angle lenses whereby you get a "cross" effect visible in the photo. You would need to google or ask on this, I have no experience directly, only vague memory from a review somewhere.
 
Filters are a must-have, believe me. Once you've used them and learned how to use them properly, you will never look back.

The simple UV will protect your lenses, and yes, it is true, sticking a piece of ultra-thin glass in front of your lenses will degrade the image ever so slightly, but over time, using unprotected lenses will lead to dust causing scratches, and repeated cleaning of the surface will remove the glare reduction coating, causing even greater degradation of the image.

But filters go far beyond just the simple UV.

Just like the writer above, I will suggest, if you have more than one lens, to invest in something like the Cokin series of filters, which will allow you to use one filter across several lenses.

There is one exception to the Cokin series, one filter that is worth acquiring for every lens you own. Grab hold of a polarizer for every lens you own, these are magnificent little must-haves, especially if you shoot landscapes. (They can even, in a pinch, double up as a neutral density).

There are some great sites to look at if you are interested in learning more about filters. Have a look at the following:

http://www.cokin.co.uk/pages/main.htm
http://www.illustratedphotography.com/basic-photography/optical-photographic-filters
http://en.wikipedia.org/wiki/Filter_(optics)

That should give you most of what you need.

Hope it helps.
 
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Many filters can have their effects simulated in software. Those that can't are more useful. Here's a list...

In order of usefulness -

* CP - Can be used to enhance an image in a way that's totally impossible with software.
* GND - Has an effect that can be replicated in software, but never with equally good results.
* ND - Specialised uses where a very slow shutter speed is required in bright scenes.
* Special Effect Filters - things like Star filters - Can often be replicated in software (if you should ever be sad enough to want to).
* Coloured filters - Can normally be replicated easily in software.
* UV/so-called 'Protective' Filters - Can easily be replicated by using the 'Blur' and 'Lens Flare' tools in Photoshop.
 
Tiffen DFX is a very good app for simulations of hardware filters. Some work better than others, but at the very least it's a good way to audition filter types before buying.

The softening filters are particularly good and infinitely tweakable. It's my goto app for beauty portraits.
 
hollis_f said:
Many filters can have their effects simulated in software. Those that can't are more useful. Here's a list...

In order of usefulness -

* CP - Can be used to enhance an image in a way that's totally impossible with software.
* GND - Has an effect that can be replicated in software, but never with equally good results.
* ND - Specialised uses where a very slow shutter speed is required in bright scenes.
* Special Effect Filters - things like Star filters - Can often be replicated in software (if you should ever be sad enough to want to).
* Coloured filters - Can normally be replicated easily in software.
* UV/so-called 'Protective' Filters - Can easily be replicated by using the 'Blur' and 'Lens Flare' tools in Photoshop.
Click to expand...

I've often wondered about these filters and how the fashion of images/affects changes over time.

I wonder if in 20 years time we'll cringe at some of the effects/shots that are "in" today. :lol:
 
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ZoneV said:
I've often wondered about these filters and how the fashion of images/affects changes over time.

I wonder if in 20 years time we'll cringe at some of the effects/shots that are "in" today. :lol:
Click to expand...

[cough]. Selective coloring. [gag]
 
ZoneV said:
Have a look into the Cokin P filter holder, an adapter ring for your lenses (couple of quid on Ebay from Hong Kong) and a set of HiTech 85mm ND filters to fit the holder (generally considered to be more neutral than the Cokin ND filters, and less expensive than Lee etc). The set has 3 ND filters of varying strengths, ND 0.3 (1 stop), 0.6 (2 stops) and 0.9 (3 stops) and can be stacked in the holder. With the right adapter rings, you could use this set with all your lenses with filter size up to 80mm (I think).

For very long exposures you'll need a very strong ND filter, often referred to as a "big stopper". These can be expensive but you can improvise using an adapted welding glass. Have a look around, there's a thread on it somewhere.

Edit: Also, a circular polarizer will add nearly 2 stops, which would be enough to turn your 2 second shutter speed into nearly 8.
Click to expand...

I started out using the above filters and found them a great introduction to using filters, small costs about £40 for the hitech set with cokin P holder. If you decide that filters are for you then you can look at moving to something like the Lee filters which imo are in a different league all together (and price:'()

Maybe worth watching the classifieds, i sold all mine on here same day :thumbs:
 
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