Focussing With Filters

There are many reasons why your lens might not be as sharp as you’d hope it to be. It could be because you need your camera and lens calibrating, or you might have a bad ‘copy’ of the lens. However, it could be the filter you were sold is degrading the quality of the lens. This blog is a few words of wisdom on those cheap ‘own brand’ UV filters.

We were contacted through social media a few days ago by a disgruntled customer (not our customer of course) who had recently bought a Nikon D7500 and a 200-500mm from a well-known retailer. This isn’t a problem, but he was also sold an ‘unbranded’ UV filter to protect the front element of the lens.


For most of us using filters is not something we put much consideration into – but maybe it should!


The customer contacted us after being frustrated and unsatisfied with the focussing performance of his new gear, despite the kit being brand new! After brief chat with him we suggested he come down the follow day so we could investigate.


First step was to check if a camera and lens calibration was needed.


Initial testing showed a +4 autofocus micro adjustment (AFMA) being required, which may not seem significant; however a +4 AFMA with a 1.5 x crop sensor will make a considerable difference – especially when shooting with the aperture wide open. This isn’t unusual, we constantly find new lenses needing similar adjustment values.


After finishing the calibration, we reset the camera, replaced the UV filter and took some tests shots. Try to read the text at the bottom of the target!



lens calibration 1


The image has been cropped by 200% to highlight the problem.



Now compare to the below where we have removed the offending filter – phenomenal eh?!



lens calibration 2


The image has been cropped by 200% to highlight the problem.



There are those perfectionists who refuse to use filters as they can degrade the image quality, even if the degradation is minimal and almost undetectable by the human eye. We totally agree with the use of protective filters, they protect the front element from scratches and are a whole lot cheaper than replacing the front element of a lens!


Nevertheless, photographers can not expect to spend £20 on a filter and expect the glass in that filter to be as good as the elements in the £1000 lens! Putting cheap (often own brand) filters on the front of a lens is parallel to putting Vaseline on the front of a lens – it’ll end up in a blurry mess as seen above.



lens calibration 3


The culprit…


Breakthrough Filters offer the sharpest and most colour neutral filters on the market. Breakthrough Photography Filters feature SCHOTT Ultrawhite B270 optical glass made in Germany, and with their state-of-the-art multi-resistant coating (which has 16-layers), gives an incredible 99.4% light transmission rate!


The 16 layer coating also creates a protective layer that’s structurally harder than the glass which repels dirt, water and other elements by beading rather than absorbing, making it quick and easy to clean no matter what you get on there.


We are not saying that you have to buy an incredible filter for your 18-55mm or cheap nifty fifty. But please, when spending hundreds or thousands of pounds, spend that bit more to get a filter the same quality as your lens. Your lens can only be as good as the quality of light first coming into it!


So next time you buy a filter, question yourself – is this filter really suitable for my lens?