Using Filters 1
Filters We will look at 4 of the most common types of the photographic filter Protection / UV / Skylight Polarising Graduated Neutral Density Filter Neutral Density Filter Dark Glass 2
Protection Filters Many people use a filter, permanently on the lens to protect the lens and, perhaps, add some other benefit No effect on exposure Protects the lens, but can result in reduced optical quality. What is your priority? Generally quite cheap, but this can result on lower optical quality Can buy straight protection filter which, ideally, has no optical characteristics UV filter similar, but reduces UV light. This is useful for film, but not for digital as the UV filter is already built into the camera sensor Skylight, similar to UV, but has a slight warming effect ALWAYS remove this filter if you are using other filters 3
Reykjavik, Iceland ISO 100, 85mm, f10, 1/125, lens protection filter 4
Polarising Filter Like polarising sunglasses, a polarising filter restricts the light passing through it It passes light waves that are aligned with the filter and blocks those that aren t. By rotating the filter you can adjust this Reflected light is scattered in all directions and it is mainly reflected light that you are blocking The effects is that reflections are reduced, haze is reduced, and colours are more saturated. It is particularly noticeable on blue skies Largest effect is at 90 degrees to the light source 2 types circular and non-circular. This doesn t refer to the shape, but the way that the polarising effect works. Circular is the most common because other filters can have an effect on metering systems Reduces exposure by 1-2 stops Moderately priced, lots of makes. Optical quality will normally improve with price. Some manufacturers make coloured polarisers 5
Hotel Laekur, Hella, Iceland ISO 100, 15mm, f5.6, 1/400, Polariser 6
Without polarising filter With polarising filter 7
Without polarising filter reflections are prominent With polarising filter reflections are reduced 8
Polariser Tips Keep clean- but be careful what you use. E.g. Filter Klear Lenspen says not to use it with polarising filters Can be used for lens protection filter when you are somewhere bright and sunny Remember it isn t just for bright and sunny weather e.g. wet foliage, 2 stop ND filter Can be hard to get off When combining with other screw in filters, put nonpolariser on first or rotating and taking them apart can be a pain White notch can be used to set the effect is you can see through the lens or want to return the filter to a pre-set position 9
Beware: wide angle and polariser has resulted in uneven sky Joshua Tree, Red Rock Canyon, NV ISO 100, 10mm lens, f9, 1/40, Polariser 10
Graduated ND Filter A graduated Neutral Density Filter has part of the filter clear and then gradually darkens towards one of the edges You use them if part of an image is considerably brighter than another often the case with skies in landscape photography You can replicate the effect in post processing or by using HDR. Post processing can only recover details that are there so cannot fully replicated a graduated filter and HDR has its own look which might not be wanted The graduation is a straight line, which can be a problem because life isn t like that The edge of the graduation can be hard or soft Graduated filters are normally rectangular and slot into a special holder where they can be rotated and moved up and down. An adapter ring is used for different lenses so you only need to buy one set of filters Although you can by screw in graduated filters these are of limited use 11
No Filter 1 Stop 2 Stop 3 Stop Cokin Graduated ND Filters 12
13
Londrangar, Snaefellsness NP, Iceland ISO 100, 15mm, f3.5, 15 sec, 3 stop grad ND, 10 stop ND 14
Without a grad filter the sky is burned out 15
In Lightroom you can see the problem a lot of details in the sky are blown out 16
This shows the photo where a grad filter was used. You can see that no details has been lost in the sky 17
Without graduated filter With 2 stop graduated filter 18
Try hand holding filters Keep clean Soft & hard filters choose carefully if you can. I prefer soft as it is more forgiving and can be used more widely Watch out for irregular subjects Careful with alignment of the graduation, especially on hard filters Watch for vignetting Graduated ND Tips 19
Buying Graduated Filters There are two makes commonly available: Lee expensive, high quality, big, glass Cokin a lot cheaper, plastic, various sizes There are other makes available I use Cokin. There are three sizes available: Small A Series Medium P Series (what I use) Large X-Pro and Z-Pro (glass) There are two holders for P Series: One that takes 3 filters, allowing you to combine them One takes only one filter, but is smaller, reducing the chance of vignetting on wide angle lenses (this can be harder to get hold of) Cokin filters can be bought in sets, reducing the cost a little You can get coloured and polarising filters as well 20
ND Filter Neutral Density (ND) filters reduce the amount of light reaching the sensor A 10 stop filter reduces the light by around 1000x Why do this: Increase exposure time this is my main use Reduce f stop There are some clever tricks with flash Increased exposure time has effects of smoothing waves, blurring water a, clouds, etc. and can have an effect on colours, often increasing saturation When you increase time you really must have something moving in the picture water, clouds, people Really long exposures can remove people or vehicles from a scene completely if they keep moving 21
Black Glass Strong ND filters (9-10 stops) are often called dark or black glass. They can be expensive, especially in the larger sizes E.g. Normal exposure is 1/125: 1 stop 1/60, 2 stops 1/30, 3 stops 1/15, 4 stops 1/8, 5 stops ¼, 6 stops ½, 7 stops 1 sec, 8 stops 2 sec, 9 stops 4 sec, 10 stops 8 sec 22
Without ND filter 1/25 seconds With 10 stop ND filter 13 seconds 23
ND Filter Tips Can be very difficult to keep clean Normal rules of composition apply Viewing subject can be difficult use live view Focusing can be difficult use live view Disable automatic focusing once you found focus I often find I end up using a very high f-stop. Try to avoid this as most lenses get softer with high f-stop values Shoot in manual mode 24
Some black glass can give a colour cast to a picture. My experience has been that the Hoya ND400 (9 stops) doesn t create a noticeable colour cast. The B&W ND 3.0 (10 stops) sometimes does, but not always. There is plenty online about this The colour cast is easy to get rid of in Lightroom or Photoshop. Converting to black and white means you can ignore this! Colour cast caused by B&W ND 3.0 filter 25
Long Exposure Tips Exposure can be difficult above 30 seconds. Set to ISO 1600 and take test shots. For every second at ISO 1600 the exposure will be 1 minute at ISO 100. Reset to ISO 100 and use shutter release Use the native ISO for your camera Have to use tripod and make sure it is steady Don t do if windy! Apart from camera shake moving foliage generally looks bad I ve had a lot of failures because of movement and blurry images result Switch off image stabilisation For shorter long exposures <5 sec use mirror lock up Disable long exposure noise reduction! With long exposures you can get a lot of noise and there will be hot pixels. You may need to adjust and edit these out in post processing. When you are reducing size to show at the club you can usually ignore this 26
Buying ND Filters ND filters up to 4 or 5 stops is easy and moderately priced Dark glass can be expensive and harder to get hold of look on line. Here are the main options: Hoya ND400 (9 stops) B&W ND 3.0 (10 stops) Lee Big Stopper (10 stops) Light Craft Wotkshop (9 stops) also variable, but some have no filter thread Much cheaper are variable ND filters. These are made from two polarising filters. Rotating them changes the amount of light blocked. I ve not tried them, but could be worth buying if you are looking to try ND filters out. I ve seen online that some can create a banding effect and the quality can be low. There are others Tiffen, etc but these can be hard to get hold of and expensive The filters can be described in a number of ways: how many times the light is reduced, number of stops or other factor: ND 0.3 2x ~ 1 stop ND 0.6 4x ~ 2 stops ND 0.9 8x ~ 3 stops ND 1.8 64x ~ 6 stops ND 3.0 1000x ~ 10 stops 27
Combining Filters You can combine filters! You may combine graduated filters to increase the number of stops available If you have bright sky above and bright water below you may use two filters, one to control each element When taking long exposure photos with the sky in them you will need to use both graduated and non-graduated ND filters to prevent the highlights blowing I often combine ND and polariser to get an extra couple of stops, but this can be fiddly and even live view can struggle to focus If you have trouble separating filters, consider buying a filter wrench 28
Some Examples 29
10 Stop ND filter plus 3 stop graduated ND filter. ISO 100, f 3.5, 4 sec Londrangar, Snaefellsness NP, Iceland 30
10 Stop ND filter plus 3 stop graduated ND filter. ISO 100, f11, 10 sec Skogafoss, Iceland 31
Jokullsarlon Beach, Iceland 32 Polarising filter (as a 2 stop ND filter) plus 2 stop graduated ND filter. ISO 100, f29, 0.8 sec
Derwentwater, Lake District 9 Stop ND filter plus 3 stop graduated ND filter. ISO 100, f22, 60 sec 33
Knightstone Causeway, Weston-super-Mare 9 Stop ND filter, polarising filter plus 2 stop graduated ND filter. ISO 100, f25, 30 sec 34
Windy Post Cross, Dartmoor 35 9 Stop ND filter, polarising filter plus 2 stop graduated ND filter. ISO 100, f22, 60 sec
Breandown from Weston-super-Mare 36 10 Stop ND filter, polarising filter plus 3 stop graduated ND filter. ISO 100, f22, 70 sec
Lapworth Locks 10 Stop ND filter. ISO 100, f32, 8 sec 37
Some Resources The Ultimate Guide To Neutral Density Filters by Peter Hill http://www.redbubble.com/people/peterh111/journa l/4421304-the-ultimate-guide-to-neutral-densityfilters Luminous Landscape article by Peter Cox http://www.luminouslandscape.com/tutorials/understanding-grads.shtml There are lots of articles and e-books. Just search 38
All text and images Copyright Graeme Tozer, 2013 This presentation was created for Webheath Digitial Photography Club: http://www.webheathdpc.com 39