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fredag 12. november 2010

Filtering the E-450

You need filters!

Yep, at least to protect the front element of your glass. If you had a film SLR or an earlier say 5mpx DSLR from another maker with different Ø and owned a pile of filters, then STOP ! Hang on with your Visa card, you can buy ring adapters to go up in size and use the old ones if they are the same or larger than your current lens(es)

Why bother with other filters than a protective UV one, everything can be done in Photoshop (TM)? Well I am a great believer that the better the image transmitted lens to sensor the better the end effect. Also it can save time: if you have a style of image you can achieve repeatedly with use of a filter, then why waste time in after effects??

The "skylight" UV (B)

Screw on and leave Skylight UV (B) filters on all your lenses, making sure they also have a thread for other filters to go on top or other accessories standard to the size mm Ø. This reduced unwanted glare and colour effects from UV rays, especially in winter where these wavelegnths penetrate cloud more than others: in film days they lead to a surprising blue tinge to winter shots, and also on very bright days when the camera was well stopped down below f11.

CCD/CMOS/NMOS vary in their sensitivity to UV and how they capture photons and register them to give noise or a white balance appearance to the blue. Since this can be corrected for by simply taking out a white sheet and adjusting to the conditions, then a UVB filter is not essential. ( the same is true of the tungsten and some studio specialist filters which "corrected" the white to a more natural or desirable "colour temperature")

But it protects your lens : it will break or scratch before the front element on the lens does, and over time, cleaning dust off will produce potential micro scratches on most types of glass, so swapping the filter is way better.

I have actually a clear glass tamron 43mm Ø on my pancake as the UVB for this strange diameter was out of stock. Clear glass itself does absorb and reflect away some UV, while transmitting visible light nearly 100% and a high percentage of infra red too. Polycarbonate absorbs a lot more UV in its clear form, and being tough ( the plastic most used in safety glasses) it may be an option if available for your Ø.

While on the Pancake 25mm f2.8, at the moment there are atleast two ring convertors from 43mm to 49 and 52 , the two most common 50mm FL prime Øs of the 1980s. Buy soon before they go out of production!!!

The ND Filter

A Neutral Density can be useful when the highlights or bright areas of the shot are too wide a dynamic range for this, ie most any camera. A good example would be wedding dresses, always bleaching out to little detail even on many pro's shots. NDs reduce overall light into camera without any other effects.

NDs are often used in landscapes and architectural images where they help reduce the maximal light areas, thus exteding the DR upwards and allowing for detail in the QTs and lower end highlights now visible through this sun glass! Conversely they therefore can reduce the DR in the shadows, extending into the three quarter tones and creating a loss of detail; this may be desirable to add some percieved depth to the image and drama. The

They also can help in portraiture using a tripod and natual light, where they have the same effect on the rounded countours of the face, adding detail and appearance of deoth to the image: too much and they do the opposite, reducing contrast and flattenting the face, which may be desirable come to think of it!

The down side of using an ND is that the shutter speed will be lower, especially if you are going to have a long depth of field. NOTE! not all NDs are truly neurtal; some have a purple tinge apparently!!

NDs are quite expensive for what you get and how often you use them: So they are most useful for the faster f2 lenses for handheld work, otherwise necessitating still subjects and a tripod. NDs are a grey colour, and available in different "densities" ie darknesses: you should ask for one which necessitates less than 2.5 up-f stops. The most feint ones may not be of use to you though.

I am popping out to get some 58mmØ ND soon.

Polarising Filters

These are not as popular as they used to be: in the 80s a rotating double element polariser was de rigeur for all SLR owners and many an upmarket compact owner too.

They have two main functions,( but work a little like an ND in outset when at their minimum darkness and aare therefore a substitute for the darker density NDs.)

Firstly they reduce glare, flare and reflections. Secondly, relating to this and general light scatter, they saturate colours. This is one reason why they are not so needed in the digital world: DSLRS like mine have a"vivid" function which just makes blue skies richer and saturates people and still life shots very like a polarising filter. After effects in software do much the same and more in manipulating the curve and colours.

Couple this to the fact that a good brand name 58mm Ø or bigger polarising filter is way over priced now, I guess this is why the ND is more popular and recommended in books. When a most open, the polarising filter will still be a lot darker than the first level ND, so stop your camera up maybe two or even three f stops. For their purpose, shooting in bright sunlight, this is often an advantage. I habitually underexposed polarised shots when using fuji/koda/ekta chrome transparencies (film !) to get very saturated seas and skies.

Double element polarising filters work like the way you test to tell if Polaroid TM sun glasses are real: light is only let through in one parallel plane through each, and when crossed over at 90' the sun glasses usually go completely opaque. In the camera filter, the density of the microscopic polarising elements (a lined pattern produced by a photolithographic patented process) is less than in sun glasses, and when rotated togther to maximum light" block", they are only about as dark as pair of good Raybans TM.

It may be most cost effective to buy a big polarising filter for your largest lens and use a step up, or two step up ring adapters to fit your smaller lenses. You can actually hold one infront of the lens once the desired darkeness is found. I used to do this with my pentax W90 35mm compact, but I think it had a non TTL meter, so results were mixed to say the least!

Polaroid used to produce SLR filters themselves, and if I remember correctly had some neutral single element filters : these reduce both overall brightness but specifically glare-flare-reflections. This is a specially THey also had, IIRC, some toned filters : skin and tobacco for example.

Gradient, Colloured and Therefore Square Kit/System Filters

The gradient tobbacco and grey filters and kits of square filters from various marks do not seem to be so popular either, and this is no doubt because people believe all-is-possible in photoshop. If I could get a cheap used set with all sorts then I would just to experiment. They come in their own carry case, but are a little cumbersome to use and vulnerable to breakages. Usually much better value for money as you could get a whole kit with the mount at about the price of 4 or 5 screw mount filters. Also you can tilt the filters and some systems allow for multiple filters.

Cokin are probably the most famous makers of such system filters, and used by pros world over. There used to be some cheap and cheerful makers, I have seen some budgets systems but there will be masses of used quality kits out there gathering dust. Hmm, i must stroll into a used shop I know!

Colin Baxter ( a name which also appears on the Digital Preview forum, wonder if it is the same guy?) was the arch proponent of the tobacco and grey scale gradient filters in the 1980s. Basically half his mountain shots looked like a "Line Squall" was passing over,if a little jobbie tinged, where a darkened sky lies over a lighter foreground. Stylish and a bit dated, they may be something I would like to revisit for one!

Other filters, like green, are maybe of use for things like macro of plants, or in black and white to produce remarkable colour subtracted shots.

The most useful for those of you who like portraiture, are the warm tone. Like some sun glasses, they give a "rose tinted" or often sun-tanned brown to otherwise "peely wally" caucaisian winter complexions. Very flattering to the subject, and they can help cover blemished, blotchy and red skin appearances.

Not that i ever used them as a lens filter: I used to use a skin tone flash filter- a light brown/yellowish acetate over the stand flashes and lamps, in studio protraiture . This worked nicely in colour, making British people look more Californians, and even in B&W where it helped hide blemishes on skin and give some more contrast, like an ND filter may help achiev ein natural light photography.


That is about as far as my knowledge of filters goes.

I am actually a biologist originally, back in the time fo Darwin it seems like now, and have studied the chemistry of photography, and to a little degree studied in optics and a l light physics amongst other relevancies.

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