Photography of Simon Galbally - f8Vision

Technical

UV Filters & Lens Hoods - Tips & Traps!

UV filters are sold to us a must – by sales staff, through fear – fear that if we don’t use one, our image quality will be reduced. However, the opposite can and is often the case!

Lens hoods, on the other hand, are an important asset, if not a must for use at all times. They often provide a significant benefit to image quality and protect images from the adverse effects of “stray light”. They are also excellent protection against physical damage from drops and bumps!

Even if you use cheap consumer lenses, a hood is the best asset you can add to your kit. In fact the cheaper your lens, the more important it is to use a lens hood. Before you spend money on other accessories, BUY A LENS HOOD.

To understand why and use your money wisely, it is worth understanding some basics of photographic optics.

Firstly, with lenses you get what you pay for. Lens design and manufacturing is a complex and expensive process. Quality lenses produce higher image quality; they require good optical design and correction of aberrations that occur as a matter of physics, which involves massive complex mathematic calculations done using powerful computers. They require high quality and very expensive glass, precision machining and coatings. And then they require quality manufacturing and mechanical deign and construction.


In taking this shot in a clean environment, why would I add a filter and run the risk of reducing the superb resolution of the Hasselblad lens? The large lens hood affers all the physical protection against bumps that the lens needs!

The Traps

But, even the very best lenses’ performance is affected by how they are used and what gets attached to them! While we seek to protect our expensive investment, that itself adds risk of something that works against their best possible performance. Equally, what we don’t add, restricts performance. The former statement relates to filters while the latter relates to lens hoods.

Optical lenses are subject to the intrusion of stray light rays which can degrade image contrast and add what is known as “flare” (there area number of types) – the appearance of light streaks and halos as well as areas of low contrast seen as pale patchy areas, which are ugly. Some types are very visible at the time of taking the image, others are not until the image is exposed later.

The more common flare caused by shooting directly into the light is not so risky because we can see it occurring very easily. But the risk of "veiling flare" is greatest when the light is strong and oblique to the lens because it is not so obviously visible in the view finder. This type of flare can be caused or just increased by adding extra glass and an area of air to the front of the lens – adding a filter!

The issue is to not increase the chance of flare as well as to optimise image quality and help protect the lens front element. It is about careful selective use of filters and always using a lens hood. In fact the use of a lens hood becomes increasingly necessary if you add a filter – to help reduce the risks of flare caused by adding the filter.

Furthermore, adding a filter could mean you are also adding lower quality glass to the front of a lens too!

So, the answer generally is that if you are wanting to protect your lens and optimise its image quality, simply using a lens hood will likely achieve both objectives without the risk of adversely affecting image quality!

In Summary

When planning to protect your lens and wanting to ensure image quality is not adversely affected by stray light and / or the need to add a filter, remember:

1. Only add a filter if it will specifically add a necessary benefit: of effects like reducing haze in a hazy environment; or, add protection against the elements during that shoot;

2. Always use a lens hood to maximise contrast and image quality by protecting the lens from stray light. Using it is even more important if you need to use a filter.

Keep in mind that using filters involves adverse optical isues of:

1. adding glass – the less the better;

2. adding potentially inferior glass to your lens glass;

3. adding a layer of air – gap between the front element and the filter;

4. adding a filter that actually may have no optical benefits except possible protection against the elements associated with that shoot.

All these issues are what the lens designer worked hard to limit or eliminate!


Taken wthout a filter, I relied upon the optical quality of the lens to avoid any flare when shooting into the strong setting sun.

Lens Protection

We are sold UV filters for 2 benefits – protection of the front lens element from damage, and elimination of UV light rays. The reality is that while protecting the lens, we may be reducing the image quality and generally we get little benefit because of the coatings already on our lenses.

In fact, a lens hood will more often provide better physical protection against pumps etc. than will a filter! So, in terms of protection, a filter’s protection is best against the environmental elements if you ensure you always use a lens hood.

Of course as a general rule it is good discipline to be prepared to add such a filter – as a method of diligent protection of what may be expensive optical glass on your prized lens. So at the outset one is very well advised to have at least one UV filter for each lens thread size in a lens kit simply because there will be times when not having that protection filter in place could be a disaster waiting to happen.

Yes, such filters are an excellent source of physical protection for the lens’ front element – against the environmental elements such as in bad weather; in damaging environments like dusty or sea-spray environments; or as protection from a nasty knock. But, as I detail further on, a filter is not the only (nor always the best) option to protect a lens.

Having started at that point then we need to ask why else you plan to add a UV filter: to protect the image from UV rays or something similar? If son then it may be a waste of money if you are using “modern” lenses – these lenses have UV coatings anyway so the filter adds nothing!

If the lens is an older uncoated or single coated version, then a UV filter just might be a good idea. But, before you run out to buy up filters for older lenses, you must consider how a filter can degrade your images.

The image above was an opportunistic snap taken with a Canon Haze filter. Any chance of image degradation was limited by the huge Canon hood I always have fitted to the lens (as I do with any lens I own). It was effective because the morning was enormously hazy (quite ugly in fact) and I knew the image had only a remote chance of appeal. In fact an A4 reproduction has very nice effect.

THE BEST OF A BAD LOT, OR THE BEST OF THE BEST

Given that for basic lens protection I will use a UV / Sky / Haze filter I ensure that the filters I have for each diameter in my kits meet most or all of the following criteria:

1. a match for my lens glass – premium quality similar type (eg sourced from Schott) or lens maker preferred (not necessarily wearing the lens makers’ badges). Glasses do differ if the come from different sources and can have different optical (tonal etc) characteristics due to differing coatings etc.;

2. offer premium multi-coating thus limiting the chance of primary and / or secondary degradation from things like flare or stray light behaviours;

3. are generally of a high quality design – such as thread quality (brass threads avoid binding), likelihood of causing vignetting, are equal to or superior to the lens quality (more applicable when putting filters on “consumer grade lenses”.

So the UV filters I use are typically B&W, Heliopan or Tiffen versions. What I like about the B&W HMC (Schneider) filters is that when used in adverse environments they resist moisture and dust sticking to the outside through a special coating. Some filters I have are lens makers items (eg Hasselblad and Leica) which I’m told are made by the premium filter companies B&W and Helliopan. All use the world’s best glass from Schott in Germany.

In the Bride Shoot image above, any filter would have been a useless / needless addition to the lens since it would offer no benefit of image enhancement, only risk of image degradation.

CONCLUSION

Therefore, before I add a UV filter (or similar) I ask myself:

1. what’s the objective – reduce UV rays? If my lens is a modern multi-coated lens then there is no benefit to offset the potential image degradation. In this situation, if the lens is not exposed to a particularly damaging physical environment (both airborne particles like water, salt air or sand blasting; as well as physical “hits” as in the case of bush-walking or climbing when you may inadvertently knock the lens front against an object) you are best advised to not have a filter on the front anyway.

So, before you mistakenly run out to vigilantly buy a UV filter to protect your lens, be sure to ask yourself the questions above.

The exception is with my single coated lens - it benefits from the UV coating on the B&W filter and it has not adversely reacted to my tests.

Above all remember what your objective is: protect the image from UV rays; protecting the front element of your prized lens. But, what you expect from a UV filter is not what you will necessarily get, so in so many cases adding one to your lens may just be wasted money! And again, consider the fact that you may be adding inferior glass right in front of expensive superior glass! When you do buy a filter, NEVER buy a cheap one! If you cannot afford a quality filter, then search for a used version in good condition, which will not be hard to find.



In the Hunter Valley image above, a sky / haze filter offered some benefit of cutting through distant haze hovering over the ranges; but, care was taken to ensure the lens hood offered glare protection due to the angle of the sun.

An example from experience

Some years ago I got the brilliant Summicron-M 35mm ASPH lens for my Leica M7. On my first outing to try out this highly regarded lens, I added a quality B&W HMC filter – feeling the wide angle aspherical lens design made this lens exposed to nasty bumps. What a silly idea! Despite the fact I was shooting with the nice lens hood, most shots in sunlight came back with ugly flare! This tiny hood has half of its depth taken up by the filter – I’d added glass and air, pushed forward the most forward glass and only had a few mm of hood protection. And, when shooting with a rangefinder camera, one does not see what one will get! I got flare and plenty of it! I’ve never used the filter on that lens since and the hood gives it all the protection it needs.


Photos and text copyright of F8Vision and Simon Galbally.