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Let me introduce our new VFFOTO ambassadors - Bryan and Patrik

BRYAN PETERSON has been a successful commercial photographer for over 35 years....more info : HERE  

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How to choose appropriate ND filter

ND (Neutral Density, neutral gray) filter stays on a photographer‘ s lenses only for a while, but, along with polarizing filter, it really comes in handy.   What is ND filter? ND (Neutral Density) filter is a gray filter, ideally without any color tint. It limits the amount of light passing to the lens, therefore reducing passing of light of all wavelengths and colors.     What is ND filter suitable for? Allows to use longer exposure time or shooting with surplus of ambient light with more dimmed lens.   Types of ND filters Neutral gray filters are divided to classic screw-on (circular, screwed on the lens), magnetic (circular, attached to a magnetic adapter) or flat in a holder (square/rectangular, placed in a holder at the end of the lens).   How to choose a ND filter There is no universal ND filter, so the decision is first and foremost on the use and purpose. What to focus on? First parameter is ND factor, which indicates the amount of stops of light and the degree of darkening, therefore the strength of the filter. For example, ND filter 8x allows 8 times less light to pass through than without it. Each manufacturer uses a different marking. Sometimes it is EV value. A shift of -1 EV means halving the amount of transmitted light, ie twice as long is needed to achieve the same exposure.   Second parameter of ND filter is a color shift, given in Kelvin. Neutral AND color shift is not a contradiction. Ideal ND filter should be completely neutral, ie lower the amount of passing light in all wavelengths of the spectrum and preserve all colors faithfully. However, in life as well as in photography, nothing is ideal.  Technology has not progressed far enough to make the ND filters 100% neutral. Manufacturers are trying to make the color shift as small as possible, especially at strong ND filters (ND 1000x and more), but one needs to reckon with that. For illustration, first generation of VFFOTO ND 1000x had a color shift of 2000K, second had about 600K. Current ND 1000x Golden Series has about 400K.   Third parameter is optical quality and mechanical design. Quality ND filters does not affect sharpness, does not have reflections or adding vignetting or even produce chromatic aberration. Therefore these conditions are met only with more expensive filters. The lowest frame is more suitable (prevention from vignetting on wide-angle lens), as well as frame made of brass than aluminum (lower risk of jamming the filters – aluminum has tendency to expand due to heat)   Fourth parameter is resilience to stains, dust and water drops. For example, when taking photos near waterfalls, close to water, the special nanolayers on VFFOTO filters will prove its value. Despite having the lens hood, water drops land on the filter glass. Thanks to the aqua-phobic treatment of the nanolayers, the drop forms a ball which is easily removed by a blowing balloon.   Fifth parameter is system of attachment of the filter onto the lens – classic screw-on, magnetic or flat in a holder. Each of them has pros and cons.     Magnetic filters Holds without screwing, by the power of the magnets. Requires an adapter screwed on the end of the lens. Pros:     • Simple and fast attached/detached without screwing or tools.     • Comfortable focusing, filter attached after focusing – accidental move of focus or zoom during filter attachment is not possible     • Possibility of combining multiple magnetic filters at one time     • Multiple magnetic filters can be stored together in a “cone” in protective case-pouch (storing each filter separately not necessary)   Cons:     • Need to store the filters when packing up, when placing the camera in the photo bag there is a possibility the filters may fall off - the magnets are not strong enough to hold on the lens when pushing against the photo bag partition     • When using the Step up ring it is not possible to use the manufacturer’s lens hood     • Not suitable for ultra wide-angle lens (adapter + magnetic filter ring is higher than the ring of the screw on filter, possibility of vignetting). Adapter and 1 magnetic filter is suitable for using up until the focus of 20 mm (fullframe), adapter and 2 magnetic filters up until focus of 24 mm (fullframe).   Circular screw-on filters Classic that has proven itself for years. Filters are screwed on the end of the lens by thread. Pros:     • Attached filter holds firmly, even when storing the camera to a photo bag.     • Circular screw-on filters can be combined – multiple filters together.     • Suitable for ultra wide-angle lens (from about 15-18 mm fullframe).     • Can be stored screwed in a “cone” together in protective pouch/case, no need to store them separately.     • Circular screw-on filters of one size can be used on multiple lenses, smaller filters as well through step up rings. Possible to add the lens hood if needed.   Cons:     • Circular screw-on filter can sometimes jam in a thread. Using a special graphite pencil can prevent it from happening.     • Screwing a filter onto the lens must be done with great caution, as during this process the focus or zoom ring can be accidentally moved resulting in ruining the set up.     • Slower handling on and off the lens in comparison to the magnetic filters.   Flat filters in a holder Squared or rectangular bars of optical glass, which are placed in a holder screwed on a lens. Pros:     • With an appropriate size suitable to be used with ultra wide-angle lenses.     • Flat filters can be combined – multiple filters in different slots in the holder at the same time.     • Ability to combine ND and Graduated ND filters.     • Graduated ND filters are easily set up by moving up or down in the holder to get the desired transition.   Cons:     • Flat filters cannot be used separately, only usable with a holder. This adds weight and space in the photo bag.     • Darker flat filters needs extra sealing from unwanted light, either on glass or on the holder.     • More complicated handling of the filter, when compared to magnetic system.   Sixth and final parameter is a diameter of the filter. With only one lens the choice is simple. Having multiple lenses with different diameters leads to a decision. You can either buy ND filters for each lens separately, which can get very expensive, or you can decide to buy just for the largest diameter along with step up ring for the smaller diameter lenses. That applies to classic screw-on filters, where you can use non-original lens hood, screwed on the outer thread of the filter. Magnetic system does not allow to use the original manufacturer lens hood when having step up ring and larger diameter filter (the lens hood does cannot hold on the filter attached magnetically).   Division of ND filters 1) Weak (ND 2x to ND 64x) Suitable for portraits (people, animals), fashion photos and video shooting. These filters are easy to see through, so focusing with the filter on is possible. Allows to work with excess of light with more dimmed lens and therefore allows to separate main motive in front from the background with lower depth of sharpness. (Side note: despite the rumors, ND filter on itself does NOT AFFECT the depth of sharpness, it serves as a mediator over the possibility to use lower aperture numbers). ND filter is invaluable when shooting a video. The amount of light can be changed with ISO and the lens hood, but lens hood especially can make the depth of sharpness bigger with higher aperture, which causes the main motive to be lost in the chaos of sharply rendered background. Shutter speed cannot be altered much (should be fixed at 1/2x of the frame rate, for example: at 25 frames per second the time is 1/50 s) so the best solution during stronger light is ND filter.   2) Strong (ND 64x–2000x or more) Suitable for landscape and tourist photography, where a tripod is necessary. In landscape photography a strong ND filter will allow to have exposure for tens of seconds or even minutes. Shooting sky with longer time results in spectacular track of moving clouds. Distinctive object (tree, church, castle,…) on the horizon, sky with clouds like from “The Simpsons” – suddelny all of them have potential for an interesting shot. Details are smoothed out for water in motion, which makes the shot simpler and clearer. However, not everyone likes the water so blurred. Seashore photos can offer pleasing effect of clear waves thanks to longer exposure. Tourist photography of sights, architecture or places of importance are usually occupied by other tourists, which is not necessarily a bad thing. Just use extra long exposure and blur them out. The trick is a long exposure of the sight. The tourist will keep coming and going, and thanks to their movement they will simply vanish. Apart from a tripod, it is good to know the camera settings. You can’t do without a remote shutter release,  which allows long exposure in the “bulb” mode (some of the cameras won’t allow delayed shutter release or infrared trigger longer than 30s, which may not be enough). ND filter 64x does not have a problem with autofocus. However, stronger and thus darker ND filters (2000x and more) can cause autofocus a hard time. The solution is either to focus before the filter is attached and then turn off the autofocus, or switch to manual mode and use the Live view. Once focused, you can attach the ND filter, and mind not to touch the lens, especially the focusing ring. Luckily, you don’t need to worry about that when using the magnetic filters.  Calculation for setting a correct exposure time is necessary (every point of EV means extension of exposure time by double). Tables, charts or modern apps can be used. We recommend our VFFOTO ND calculator app.   In conclusion It is better to have ND filter than don‘t.  And it is even better to have a quality VFFOTO ND filter. Weaker ND filter (2x to 64x) for portraits or shooting videos. Stronger ND filter (64x to 32000x or even more) plus a tripod with remote shutter release for landscape and tourist photography.   We wish you to have a good light at all times! Jiří Skořepa, VFFOTO technical specialist

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