All of us got used to a lens in the camera, and already very few people reflect that this, at first sight, simple device is actually so difficult. And, however, first of all quality of the received image depends on a lens. Therefore at a choice of the camera it is not necessary to pay attention only to treasured number of megapixels and number of functions. As the theater begins with a hanger, so the camera begins with a lens. And not for nothing its cost in serious models reaches 60% of cost of all device.
It is natural that with all responsibility to approach a choice, it is necessary to represent, the lens as it is arranged what types happen why is necessary and how to define what is necessary to you. Here about it the speech will also go. InfoAdvisor.net will begin, by tradition, from the theory.
The lens includes optical system in the form of one or several lenses (including lens components – the lenses which are stuck together among themselves), and sometimes and the mirrors concluded in the general frame. The frame
is no other than the lens case. It serves not only for keeping of all components, but also for their correct adjustment (adjustment of their relative positioning). I.e. all elements have to settle down with rather high precision, especially notorious optical axis. And what this such, and why it notorious?The optical axis
is the center of symmetry of an optical body, i.e. the imagined element. And in other words – the diametrical center of lenses.
The frame is carried out under concrete type of devices that defines compatibility a lens device. The simplest frame contains: blackened inside and, as a rule, outside a tube in which lenses or lens components which in multilens devices are divided into two groups – a lobby (outside of the device) and back are established, between them have an iris diaphragm.
Problem of optical system – to project the image of the necessary size on a surface of a film or a matrix. And it becomes so.
The light source in the theory is considered as the shining point radiating an unlimited stream (bunch) of beams. If on the way of this bunch to put a diaphragm, i.e. the screen which is not passing light with an opening inside, the beam of light will be limited that will lead to reduction of amount of light (decrease in illumination). In a lens the maximum quantity of light capable to pass through its optical system is limited to the internal diameter of a frame. The more diameter of a frame and, therefore, lenses, the more will pass light and the better the screen is lit. The lens becomes with bigger svetosily. Running forward, I will tell that the more diameter, the better in many respects. It, for example, allows to reduce effect of "vignetting" and to expand photographic width. But in more detail will tell about this InfoAdvisor.net further in the text.
Reduction of a diaphragm it is possible to achieve narrower beam of light that will even more strongly reduce illumination of a shot and will increase sharpness depth. And here to allocate a separate beam from a bunch, having reduced a diaphragm to the maximum value, it is impossible because the phenomenon of diffraction of light begins. Thus beams lose straightforwardness and start bending around edge of a diaphragm. And than it threatens?
It is known that use of the maximum opening of a lens leads to reduction of depth of sharpness and emergence of the specified "vignetting". To increase depth of sharply represented space and to avoid the specified effect, it is necessary to zadiafragmirovat a lens. But sharp (accurate) subjects in a shot will be only till certain time. When diffraction begins, the image will become indistinct, indistinct. Therefore it is more favorable to choose lenses with a big diameter. It increases the width of use of its opportunities. But shortcomings of optical system do not come to an end with the diffraction phenomenon.Light refraction
is a change of the direction of light when passing through the transparent polished (smooth) surface, for example, through a lens glass surface.
Thus the part of the world, refracting on border "air - an optical body" (further – the lens) passes in it, having changed thus a corner (<β), а часть отражается от поверхности под углом равным углу падения (<α и <α'). При этом углы преломления и отражения лежат в одной плоскости, взаимопереместимы и зависят от величины угла падения, т.е. углы β и α' изменяются пропорционально изменению угла α.
The phenomenon of refraction leads to emergence of aberrations
(distortions of the image). In optical systems apply various receptions to their decrease, as a rule, the demanding increases in number of lenses.
But on it problems do not come to an end. The matter is that index of refraction, and, therefore, and a corner, depend and on structure of light passing through a lens. Everything is simple, if light monokhromatichny, for example, yellow for which indexes of refraction are given in tables. Then light simply changes the direction. And when passes a bunch of this world, "focuses" begin here. Namely. This world consists of a set of flowers which have various indices of refraction. It leads to "stratification" of a bunch.
The biggest corner at violet color, and the smallest – at red. This phenomenon is called as dispersion
Likely you saw a rainbow after a rain when the Sun looks out is and there is a chromatism of a sunlight in the smallest drops (aerosols) after a rain. This feature significantly complicates a task to developers of optics for the color photo. And in this plan the color photo significantly differs from black-and-white where chromatism practically does not play any role.
Is also the amusing moment. If light can enter a lens at any angle, here leave it it can not to turn out.
It is connected with that the phenomenon of refraction arises on each border of transition (air lens and a lens air). And so at excess of a hade of light on an entrance to a lens (the first border) light on the second border (at the exit) refracts so that gets back to a lens and goes in cycles there, creating a certain noise. Only to listen it is useless, since noise this light, but not acoustic. But result is that light in this case will not leave a lens at all. That brings, naturally, to restriction of a viewing angle (field of vision).
And now that regarding reflection. Reflection of light from a surface practically does not influence quality of pictures, unless reflections on internal lenses in any way. But it significantly reduces light stream. To lower losses of light apply an enlightenment of lenses. Without going deeply into details, InfoAdvisor.net will tell that it is reached by drawing on a surface of lenses of a film of special structure. Thickness of this film is accurately determined and will be coordinated with the middle of a visible range – with green color. T.o. the best svetopropuskaniye, if I may say so, turns out for beams of green color. As, however, and at an eye of the person.
It is also necessary to notice that the lens with a big diameter of lenses where is better, than "dwarfs". Why? And it is connected not only with above the specified advantages, but also with decrease in aberrations, the caused curvature of lenses. The matter is that the quantity of aberrations increases with increase in curvature of lenses. And the more diameter of lenses, the less curvature, i.e. they become more flat.
Now, having though small idea of the device, we can start a lens choice. To be more exact, that, most likely, you will buy the camera completely. But not to be mistaken and to choose improper option, I will provide some recommendations.
How to choose a lens?
So, you came to shop, and your eyes ran up on regiments of show-windows. How to define, which yours? Here it is necessary to be defined at once that for the device to you it is necessary and for what (we spoke about it in the previous ). There is an important moment is a fastening of a lens to the device. And types of this fastening happens only two: zhestkovstroyenny and removable (replaceable). The majority of devices has the first type and only "reflex cameras" possess removable lenses.
And for what all this is necessary? The Zhestkovstroyenny lens as you likely already guessed, is an integral part of the device, and it is impossible to remove it. There would be seem and is no need. And actually there is no need if you quite accept opportunities and quality of a regular lens or as still call it, a Kit-lens. And if is not present? If is not present, then in this case you will already do nothing since there is no opportunity to replace a lens.
And now let's understand, why it to change. There are various motives.
First, this quality. You finished shooting material and its quality you extremely does not arrange. Here then it is necessary to reflect on possibility of change of a lens.
Technical quality of a lens is defined generally by technology (including the speed of technological process) cookings of glass for lenses and quality of their including manual operational development. The matter is that glass, as well as any amorphous body, has the unpredictable temperature of melting. If temperature podymatsya quickly, glass can not only melt, but also begin to boil that will lead to emergence of vials of air in it which will stiffen then in a lens forever. To avoid it, it is necessary to warm glass slowly and to stop further increase in temperature as soon as glass thaws". Naturally, it is much more sluggish and expensive process.
And than bubbles are terrible? It is not difficult to guess that bubbles it is an obstacle for light and border of transition where there will be again above specified processes. The more bubbles, the image will be worse. Try to look through corrugated glass. What did you see?!
And plays not only quantity of bubbles, but also their size large role. In the domestic lenses "Helios", for example, about four bubbles of the visible size were allowed. In foreign optics, as a rule, you will not see them. No!? You after all noticed? Then it is the cheapest optics. Even in simple inoobjektiva I did not meet bubbles yet. Stop! And how they look? That it is better to see them, it is necessary to remove a lens (if it is possible) and to look at lenses at a gleam. Bubbles look as foreign impregnations. If their diameter is very small, as the black points reminding garbage. If a lens fixed to find bubbles where it is more difficult. The good light source sent to a lens is necessary. At survey it is also necessary to pay attention to purity of the first lens. It has to be pure, without scratches and stains.
And here you since the difficult equipment for this purpose is necessary will not manage to define correctness of geometry of lenses.
Secondly, use of interchangeable lens is connected with need of change of focal length. But allow, there is a zoom!? Yes, it is but if your requirements are wider than the offered zoom range, you need to expand it by means of other lens. At the majority of regular lenses the range of an optical zoom is very small. Especially as it is impossible to make (for technical reasons) a lens with very wide spacing of focal lengths. There are cases when supershort focal lengths are necessary, then " lenses a fish eye" will be necessary for you ("fish eye").
Or, on the contrary, you want to remove on superlong distances, and then you will be already needs a telephoto lens with equivalent focal length in 500 or even in 1000.
Here in these cases interchangeable lens – a thing irreplaceable. But such addictions are very unprofitable since demand existence of expensive reflex camera and very expensive lenses in the assortment. Therefore such option is suitable either for professionals, or for fans of the photo. And, if you do not treat neither those, nor another then it is necessary to reflect, whether the device with possibility of change of a lens is necessary to you.
Many difficulties are behind simple change of a lens. The matter is that to approach the device not what to you will there is a wish lenses, and, as a rule, only original and only certain models. As the original it is understood that the same producer (system). For example, the lens Nikkor which is calculated on the devices Nikon will not approach the device Canon.
Of course, there are ubiquitous third-party producers such as Sigma, Tamron, etc. which let out the wide range of production for different devices. But also here not everything is so smooth. For example, the device Nikon it is possible "to make friends" with any lens Nikkor or its analogs (a bayonet joint like F). But you should not think that everything comes to an end with mechanical compatibility. If you on the modern device pulled down "old man", it does not mean at all that you receive all functions declared in the device. Also any functions on lenses of third-party producers can not "go".
Why? Everything is simple! But before learning about relationship between the device and a lens, InfoAdvisor.net will tell how, actually, fastening of a removable lens is carried out.
Distinguish two types of fastening
: carving and bayonetny. The carving
was applied long ago, in completely mechanical devices, and in the foreign – long ago.
It is not difficult to guess that the lens in this case privorachivatsya to the device on a carving for what it is necessary to get at first to calling of a carving (and it happens difficult, since a carving small), and then to turn a lens on some turns.
Likely the only plus is a low cost of a design. And there is a lot of minuses. The longest is a process of change of a lens. It very much and very sluggish. It does inapplicable this type for the shooting demanding frequent change of lenses. Besides, you risk to receive unsharp images because of an incomplete tightening or a samootvorachivaniye of a lens; impossibility to make an electronic lens; potentially the worst adjustment.
The second type – a bayonet joint
. Here for fastening it is necessary to combine points on a lens and the device, to drown a lens against the stop and to turn it clockwise (if to look at frontal part of the device) to a zashchelkivaniye. Elementary and quickly!
Now this type of fastening completely forced out the first since has no those shortcomings. And opportunity to allocate a lens with "intelligence", i.e. to make it electronic has such advantages as speed and clearness of accession and a detachment, high reliability of fastening with a stable and exact adjustment. Minuses: higher price, existence of a large number of different and incompatible types of bayonet joints that leads to complication of a choice of optics.
So, also we will talk about the last in more detail.
Now practically each firm tries "to cause a stir" and make the camera of an own design, explaining it to the know-how or credo. And gives it to that only a limited number of interchangeable lens is suitable for the concrete device. And, apparently, that in it special. And here that! You, say, picked up the lens suitable you in parameters and it extremely is pleasant to you moreover and its price is much more tempting, than at the navyalivayemy original. But far from it! It does not approach. And in such situation two decisions. Or very much to save for the suitable original. But there is a probability that when you save up, it will already not be actual for one reason or another. Or to try to make friends the "quarrelled" couple. And here, unfortunately, there are a lot of difficulties.
And the first – whether approaches a bayonet joint. If approaches, it is already good. And if is not present? That too anything terrible! Achievements "Kulibiny" are high and there are adapters from one type of a bayonet joint on another. Here it is necessary to pick up an adapter necessary to you only. But it is necessary to consider that the majority of firms with an exit of new model change bayonet joint type, and it is necessary to be guided not by , and by device type. By the way, it becomes specially that old lenses did not approach and, on the contrary.
And than application of an adapter threatens? It was almost without serious consequences possible to apply them only on completely mechanical chambers. Whereas in modern devices in that case you lose all "delicacies", including an auto focus. Why? And communication between the device and a lens will be lost. Also can happen so that the device in general will refuse to work since "will consider" that it has no established lens.
If to remove a lens and to take a detached view of it a bayonet joint, you will see a set of contacts.
Yes! Through these contacts the chamber "communicates" with a lens. Naturally, the adapter will deprive of this opportunity at all.
But even if you also did without adapter, be not under a delusion. Though the lens suitable on fastening can not approach under protocols of the interface, for example. Then will be as in a saying – "yours washing, understanding is not present". At least, at best, you can simply receive less any functions. And what to do? After all it will be offensive, and the economy will be unreasonable. And it actually so! Therefore if you burn with desire to carrying out experiments with alternative (stereotyped) optics, prepare for surprises. Here before purchase it is necessary to learn everything and carefully to weigh. And suddenly, those functions which "did not go", to you and to anything! Then it will be option, optimum at the price.
But InfoAdvisor.net after all advises you to take the device with itself in shop then not to be disappointed in expensive and appeared useless purchase. As you likely guessed, the device is necessary for immediate fitting and check.
In other words, application of alternative optics is connected or with economy, i.e. to buy a lens of the same level, but is cheaper. Or for the cost of the original to buy better substitute. It is connected with that originals – very untwisted brands, and cost is added also for a name of the producer there.
And if there is a desire to enjoy original optics and, the most important, means then everything is simpler dispose to it also. We open the instruction to the device, there we look for information on applicability of interchangeable lens. For a campaign in shop you also need device model, type of a bayonet joint and desirable characteristics of a new lens(es). If the type of a bayonet joint can be not specified since it automatically follows from device model, it is necessary to deal with characteristics in more detail.
Advancing events, I will tell that it is besides better to take the device in shop. At least to be defined, what lens(es) suit you best of all. Means, of course, not in that plan what are better fastened, and for result – the photo. It is possible to look at the benefit on a tsifrovika at once. By the way, in specialized shops there is a possibility of a conclusion of the image to the big screen, for example, of the TV or the monitor. This opportunity should use.
And with the original and recommended lenses of problems will not be, they will approach not only on fastening, but also all put functions will work for them. And also it will not be necessary to puzzle in size of a working piece.The working piece
is a distance from a landing flange of a lens to a photosensitive surface. And if in an original lens it automatically is established by bayonet joint type, with analogs, and especially at application of adapters, affairs are where is worse. What's the problem? Quality of focusing directly depends on a working piece. If to change this size, the scale of distances will be displaced. T.o. depending on in what party the size of a working piece changed, focusing will be incorrect or at the beginning of a scale (at small distances), or in the end (on big). How it will affect? No, you will receive shots sharp since the auto focus functioned, but the range of focusing was narrowed. For example, if at normal value of a working piece focus was achievable with 1 m, at an aberration it can turn out guide at sharpness only from 3 m. It can limit possibilities of portrait shooting.
And with the size of a working piece not everything is so cloudless. This size does not depend on focal length of a lens. It means that at lenses (for one type of the device) with focal length 20 and 1000 working pieces are equal. Change of nature of focusing in this case is put in a lens design. And here in a film chamber or matrixes in the digital depends on geometry of a personnel window directly. To project a shot so that focus of the image fell just on the photosensitive plane, it is necessary "to play" a working piece. For example, you have the film device with a size of shot of 24*36 mm, and it on a diagonal of 43 mm, the normal lens will be 50 with equivalent focal length (it is accepted conditionally 50, but not 43). For the digital device with a size of matrix of 14,4*21,5 mm and a diagonal of 26 mm a normal lens with equivalent focal length 28. T.o. despite different sizes, a lens it turns out normal, i.e. displaying prospect without distortions. Here therefore those sizes which are applied on a lens frame, are called as equivalent focal lengths
. As you understand, the working piece in the given examples will significantly differ.
Worst of all that in most cases you will not find data on a working piece. Also it is necessary to understand that for a choice of analog you need to know the concrete size of a working piece. If it is not known (it is not specified in the instruction), you will need only to hope or for experience of sellers which is very subjective, or on existence in shop of catalogs with the specified data or tables of interchangeability.
Here, at last, you decided on it. Now came it is time to choose a lens in such parameter as focal length
. And it is necessary to choose, whether there will be it fixed or to variables (with a zoom). Though at first sight everything is unambiguous – of course, a zoom, but actually it not absolutely so.
Big plus of interchangeable lens with a zoom or as they are called, varioobjektiv is possibility of change of focal length without manipulations with several lenses. Besides, an important factor is besstupenchaty (linear) change of focal length therefore it was called vario – besstupenchaty. From minuses – big cost. And potentially more poor quality because of need of the compromise solution.
If you want to buy for the same money a lens better then it is rational to look narrowly at a lens with the fixed focal length, to a so-called fix. Lack of the mechanism of a zoom does them cheaper, more reliable and more qualitative. The adjustment of optical system in such lenses is, as a rule, more exact. Besides, quality of a prorisovyvaniye is better because of uncompromising stand of the constructive decision. However, it is subjective since for someone the best prorisovyvaniye with the extremely accurate details will be worse. Here very individually. But at all advantages of fixes, you receive also shortcomings of a type of need more often to change lenses; step (discrete) change of focal length which is possible only at change of a lens, and it pours out in need to have a large number of lenses of different focal length that is very unprofitable.
As a certain compromise it is possible to consider acquisition of two varioobjektiv, for example, one with focal length 20 … 80, and the second – 80 … 200.
For shooting of portraits the most suitable portrait lenses
with focal length from one to three diagonals of a shot, i.e. approximately horizontal corner of a field of vision from 18 to 45 °. But it is very conditional since after all in the photo there is no clear boundary.
Differ as well systems of lenses and quantity of lenses in them. Are most widespread: "Canon"; "Nikkor"; "Olympus"; "Tessar"; "Sonnar", etc. Among the domestic – "Helios" and "Industar".
And now let's deal with quantity of lenses
. As InfoAdvisor.net found out at the beginning of article, increase in number of lenses achieve reduction of aberrations. The good invention, but it only at first sight all so grandly and nobly, and actually all a little differently would seem. Yes, the level of aberrations decreases, but together with aberrations also light is absorbed. The lens becomes as it can be spoken, more "dark". The more lenses, the reflected light there are more than borders of transition of light more (thus the lens component from several lenses should be considered as one element). It leads not only to decrease in a light stream, but also to emergence of light noise in a lens that can cause a parasitic flare (that, by the way, often meets at video cameras because of simplicity of a design of a lens at it).
Than all this threatens? Loss of a svetosila and decrease in photographic range, i.e. width. In other words – reduction of opportunities. Especially it affects telephoto lenses, at which and so deficiency of a svetosila. In them use small quantity of lenses (up to 2).
Yes, you will tell, but do not do lenses with 1 lens now. Correctly! I will tell more, all lenses contain not less than 3 lenses, so-called triplets
. For example, Tessar contains 4 elements in 3 groups – the 3rd and 4th lenses are stuck together and form the third lens component. This decision allows to receive a big svetosila and smaller number of aberrations, than at a traditional triplet. Tessar gives rather accurate and contrast image therefore it was named "an eagle eye".
And here Sonnar which in fact is too evolution of a triplet, i.e. having, as a rule, 3 groups of lenses (seldom 4 groups), has depending on a concrete design from 4 to 8 lenses. Possesses rather big thickness of components and smaller number of the optical surfaces adjoining on air. It improves contrast of the image and reduces aberrations.
And now we will talk about a diaphragm
. As it was already told, the diaphragm limits a light stream and increases sharpness depth.
And, apparently, what here to choose? Of course, you will not be able to choose a design. But will be able to choose a lens on the maximum relative opening. Also it is not necessary to chase lenses, at which this value 1:2, 1:1,5 and even more. A lens with a relative opening 1:1 it is good, but is very expensive. It is quite enough to have this value ranging from 1:2,8 to 1:3,5 or even 1:4 (for normal focal length). Why?
Here you got a very expensive lens with a relative opening 1:1. And what you with it will do? Extremely seldom it is necessary to use a relative opening more than 1:2,8. Then why to overpay for not used opportunities?
And how to define data of a lens? As a rule (but not always), on forward part of a frame of a lens (where a forward lens) the inscriptions including its name, type (model), and also a mysterious inscription, for example, 2,8-4,8/24-120 are put.
What is it? And here that. The numerator of fraction is a value of the maximum relative openings. A denominator – equivalent focal length. So designation on a varioobjektiva looks. It says that the lens with changeable focal length ranging from 24 to 120 and thus the maximum relative opening will change from 1:2,8 to 1:4,8. I.e. at focal length 24 relative opening will be 1:2,8, and at 120 – 1:4,8.
At fixes only one size, for example, 2,8/24 will be specified.
Two more factors depend on a relative opening: effects of "vignetting" and "side".
The effect of "vignetting" is shown when using bigger value of a relative opening and vanishes at a masking after the third step.
By the way, I did not tell. As it is known from mathematics, the fraction 1:1 is more, than 1:2. Therefore also a relative opening 1:1> 1:2, i.e. it is more also a svetopropuskaniye. This effect is shown in the form of blackout of edges of a shot.
And so why lenses of big diameter are necessary! To avoid "vignetting", it is only required to close a diaphragm not less, than on 3 steps. But it will cause reduction of a light stream that will adversely affect quality at lenses from the small svetosily. Besides, in this case use mainly of the center of lenses begins. On the one hand it is good, since resolution of the central part where above, than on suburbs. But lenses of small diameter have big curvature, than their big "colleagues". It leads to increase in aberrations. T.o. unambiguously, the more diameter of a lens (lenses), the better.
The name of effect "side" came from the country of a rising sun – Japan and is translated as "blurring". It is very subjective art term. The effect "side" is shown with a small depth of sharpness. And interest here not in sharply represented subjects, and in what did not enter a sharpness field. Here of degradation of a background also gets under definition of effect "side".
For what degradation is used? As a rule, for separation of a background from a shooting subject. T.o. the background turns out, is washed away, and a shooting subject on it – accurate. This deliberate action. But, apparently, then it is not important at all as thus the background is washed away, the objectives after all are achieved – the object is accurately separated from a background. Yes, it is separated! But the photo, it first of all, art which demands a harmonious shot. And nature of blurring which soothingly affects the viewer, it is very important.
And now in practice. In photoequipment it was possible to apply safely the diaphragm consisting of 2 petals blinds as it becomes in many video cameras. It is a simple and cheap design. And why it to complicate? And here why.
At a masking such diaphragm blind light spots appear not spots, but rectangles of the wrong form extended along an axis of blinds of a diaphragm at all with diffuse edges that creates very unattractive picture. If on video such passes since a plot there dynamic and an eye of the person does not manage to consider a form of small subjects, on a photo it strongly is evident.
And the best effect "side" can be reached at the most round opening. But it is possible only at completely open diaphragm. A frame of lenses round – effect the best. But business changes as soon as you start blinding a lens. The iris diaphragm consists of a set of the petals creating a polygon when closing. The number of these corners depends on number of petals, and than their is more, especially round the opening turns out. And just at the beginning of a scale the diaphragm has more angular form.
However, with development of technology and emergence jumping, and also diaphragms with the automatic drive as in the majority of modern devices, it is not possible to make the mechanism with a large number of lamels since it excessively increases complexity. Therefore are, as a rule, limited to number 7. Why 7? As it became clear that the best results in respect of effect "side" can achieve only at odd number of lamels. Here also chose "golden mean" – 7 since 5 it is already small, and is already problematic to do 9.
Here so it looks in a picture with the maximum relative opening (f = 2,8).
And here so with f diaphragm = 4.
Look as the diaphragm influences the prorisovyvany Sun. In the first case the maximum relative opening of f = 2,8, and in the second – f = 16 was applied.
The diaphragm added to the Sun beams. In this case (at f = 16) the art effect from a masking is more pleasant.
Rules of the address with lenses
In the conclusion of InfoAdvisor.net has to tell that a lens as optical system – a thing very gentle and vulnerable. And whatever it was, it needs the correct and careful attitude. In order that any lens served long and truly, it is necessary to carry out simple rules:
- not to touch a lens, it will relieve you of its cleaning;
- not to clean a lens without emergency since any mechanical influence harmful influences an enlightenment. If after all decided, only a soft and pure rag, for example, a flannel. If cotton wool, only x / B. Do not apply solvents! Even from alcohol there are stains and a whitish film. Breathed – wiped without excessive pressure;
- not to subject to mechanical influences, not to strike;
- if you came to a frost from the warm room or on the contrary, give to the device "get used". Especially upon transition from a frost to heat. Fogging of lenses and a heatstroke far is not good. As good advice I can suggest to pack the device into a plastic bag of the suitable size and to put in a bag. The package improves the thermal mode and interferes with moisture penetration;
- try not to hold a lens opened without need, use a lid;
- do not bring the device in rooms with hostile environment.
Here actually and everything that I wanted to tell on lenses. I hope, this information is useful to you. Knowing at least bases where it is easier to make a choice.
The important role in a choice is played by addictions of the specific person. For example, if you the ardent supporter of Canon, you do not even look at Nikon. It, alas, is not always good since you purposely narrow the choice.
Though you will also prove that Canon is many times better than all other together taken, but it not absolutely so. At each option the pluses and minuses, but in general production is in one class approximately at one technological level. Yes, as it was already told, draw lenses differently, but this factor subjective and if it is pleasant to one as draws Canon, another can praise Nikkor, the third – Olympus. And all will be in own way right. Here to solve to you. As they say – on taste and color …