Brezzrcalni fotoaparati postajajo vse bolj priljubljeni ne le pri amaterskih fotografih, ampak tudi pri profesionalnih. Z opustitvijo zrcalnega sistema v fotoaparatu v korist elektronskega iskala in/ali LCD-zaslona je fotoaparat lahko kompaktnejši, lažji in ima manjše zamenljive leče kot njegov dvojnik DSLR.

Če uporabljate senzorski sistem, podoben tistemu, ki bi ga našli v telefonu, je lahko nekoliko presenetljivo, da imajo brezzrcalni fotoaparati še vedno zaklope.

Medtem ko vam bo vaš mobilni telefon ponujal možnost, da še vedno slišite dobro znani zvok zaklopa fotoaparata prek zvočnega posnetka, vam brezzrcalni fotoaparat še vedno daje možnost, da se to dejansko zgodi. Čeprav obstajajo različne vrste zaklopov, je vključitev zaklopa na brezzrcalne fotoaparate pomagala prepričati številne profesionalne fotografe, da so zamenjali svoje zajetne fotoaparate DSLR.

Ne glede na to, ali ste izkušen fotograf ali povsem novi, je skrivnost, kako izboljšati svojo fotografsko igro, vedeti, kako in zakaj deluje vaš fotoaparat. Kot so pokazali telefoni s kamero, bi brezzrcalni fotoaparati zlahka delovali brez zaklopov, a dejstvo, da ne, bi vam moralo dati nekaj namigov o tem, zakaj bo brezzrcalni fotoaparat (na splošno) boljši od telefona s kamero. Torej, odkrijmo, zakaj imajo brezzrcalni fotoaparati zaklope.

Kako delujejo polkna?

Sistem zaklopa v vašem fotoaparatu je stvar, ki se odpre, da prepusti svetlobo in osvetli film ali digitalni senzor, kot je to v primeru digitalnih fotoaparatov. Zapis svetlobe na film ali elektronski senzor je tisto, kar naredi sliko.

Večina kamer ima možnost nadzora, kako dolgo je zaklop odprt ali kako dolgo je film/senzor izpostavljen. To lahko naredi fotograf ročno ali samodejno s kamero.

Kako delujejo mehanske naoknice?

Obstajata dve vrsti zaklopov fotoaparatov, ki jih lahko najdete na brezzrcalnih fotoaparatih, mehanski zaklopi in elektronski zaklopi. Tradicionalno so bili zaklopi fotoaparatov vedno mehanski in iz tega sistema izvira znani hrup pri fotografiranju.

Mehanski zaklopi DSLR

Da bi razumeli, zakaj brezzrcalni fotoaparati uporabljajo mehanske zaklope, je pomembno najprej razumeti, kako deluje sistem zaklopov v DSLR, saj je bil prilagojen temu. DSLR uporablja zrcalno škatlo, ki fotografu omogoča, da vidi natančno sliko, ki naj bi bila zajeta na elektronskem senzorju. Elektronsko tipalo sedi za zrcalnim ohišjem, zato ga je treba premakniti s poti, da lahko zajamemo sliko.

Ob pritisku na sprožilec se zrcalno ohišje obrne navzgor izven poti senzorja. To je tudi razlog, da pogled skozi iskalo postane črn. Ko se ogledalo obrne navzgor, razkrije senzor, ki je prekrit z zaklopom. Zaklop se bo nato premaknil od zgoraj navzdol in razkril senzor ter omogočil svetlobi, da ga zadene.

Po dodeljenem času se bo drugi zaklop premaknil od vrha proti dnu senzorja in ga obnovil. Zrcalna škatla se bo nato obrnila nazaj in vrata zaklopa se bodo ponastavila in pripravljena za snemanje nove slike.

Mehanske brezzrcalne naoknice

Kot že ime pove, brezzrcalni fotoaparati nimajo zrcalne škatle ali pentaprizme za projiciranje svetlobe v iskalo. Namesto tega brezzrcalni fotoaparat uporablja elektronsko iskalo ali LCD zaslon, da prikaže sliko, ki jo nameravate zajeti.

Senzor brezzrcalne kamere je dejansko nenehno izpostavljen svetlobi, ki prihaja skozi kamero, vendar se slika »shrani« šele, ko pritisnete sprožilec. Do te točke kamera snema svetlobo, ki zadene senzor, tako da lahko fotograf vidi sliko, ki jo namerava zajeti, skozi elektronsko iskalo ali LCD zaslon.

Ko pritisnete sprožilec, se vrata zaklopa dvignejo od spodaj navzgor in pokrijejo senzor. Zdaj bo senzor začel osvetljevati (ali shranjevati/zajemati sliko) in vratca zaklopa se pomaknejo nazaj navzdol. To omogoča senzorju, da posname in shrani svetlobo, preden se druga vrata zaklopa premaknejo od zgoraj navzdol, da obnovijo senzor in s tem ustavijo osvetlitev (ali shranjevanje). Končno se bodo vrata ponastavila in pripravljena za zajem nove slike.

Zakaj brezzrcalni fotoaparati še vedno uporabljajo mehanske zaklope?

Ko so vsi fotoaparati uporabljali film, so bili zaklopi bistveni za zagotavljanje odlične fotografije. Vnaprej razvit film je občutljiv na svetlobo, kar pomeni, da če bi vaš fotoaparat nenehno dopuščal, da svetloba zadene film na enak način, kot to počne brezzrcalni fotoaparat z elektronskim senzorjem, bi na koncu dobili le kup preosvetljenih, belih slik.

Torej, edini način, da zagotovite, da ste posneli pravilno osvetljeno sliko, je bil, da pustite, da svetloba pade na film le določen čas. Medtem ko je razvoj elektronskega senzorja pomenil, da lahko zdaj senzor vklopite in izklopite s pomočjo zaklopnih vrat ali brez njih, še vedno ostajajo v nekaterih brezzrcalnih fotoaparatih.

To je namenjeno predvsem odpravljanju težave s šumom slike, ki ga opazite pri fotoaparatih brez zaklopa, kot so telefoni s kamero in fotoaparati z usmeritvijo. Pri teh kamerah senzor nenehno prejema svetlobo, zato mora kamera nenehno pošiljati energijo senzorju, da jo posname. Vendar, ko fotograf pritisne sprožilec, to senzorju pošlje val še večje moči, da zajame sliko. Ta dodatna moč deluje na enak način kot dodaten (ali povečan) ISO – poveča šum.

Prihodnji napredek v tehnologiji lahko pomeni, da bodo brezzrcalni fotoaparati, ki jih uporabljajo profesionalci, sčasoma prav tako brez zaklopa, vendar za zdaj kakovost ustvarjenih slik ni dovolj dobra, da bi upravičila uporabo zaklopa.

Prednosti uporabe mehanskega zaklopa

• Bolja sinhronizacija z bliskavico – mehanski zaklopi običajno omogočajo uporabo bliskavice pri višjih hitrostih kot elektronski zaklop.
• Zmanjšajte hrup, ki ga imate pri fotoaparatih brez zaklopa
• Zmanjšajte popačenja Rolling Shutter – Rolling Shutter (vrsta elektronskega zaklopa) lahko pogosto povzročijo stransko popačenje slik, zlasti če se fotoaparat hitro obrača ali se motiv premika.
• Z utripajočimi svetlobnimi viri se spopadajo bolje kot elektronski zaklop

Slabosti uporabe mehanskega zaklopa

• Zmanjšana najvišja hitrost zaklopa – Mehanska narava teh vrst zaklopov pomeni, da je največja hitrost običajno nižja kot pri elektronskih zaklopih
• Imajo življenjsko dobo – ker imajo mehanska polkna gibljive dele, so očitno nagnjeni k obrabi in lahko čez čas prenehajo delovati. Večina fotoaparatov, ki so opremljeni z mehanskim sistemom zaklopa, bo imela "štetje zaklopa" ali kolikokrat je zaklop mogoče uporabiti, preden lahko začne odpovedovati.
• Tresenje fotoaparata – premikanje vrat zaklopa in zrcala lahko povzroči manjše tresenje fotoaparata, čeprav lahko vgrajena stabilizacija slike to zmanjša.
• Odzivni čas – Spet zaradi mehanske narave zaklopov lahko pride do manjše zakasnitve med pritiskom na sprožilec in fotoaparatom, ki posname fotografijo.

Tole je povedal Robert Hall o sistemih zaklopov na brezzrcalnih fotoaparatih:

Kako delujejo elektronske naoknice?

Razvoj elektronskega senzorja je prinesel tudi razvoj elektronskega zaklopa. Te vrste zaklopov delujejo na enak način kot mehanske zaklope, saj osvetlijo svetlobo za določen čas, da zajamejo sliko.

Za razliko od mehanskega zaklopa pa elektronski zaklop deluje tako, da senzor vklopi in znova izklopi. V brezzrcalnih fotoaparatih se običajno uporabljata dve vrsti elektronskih zaklopov, navojnih zaklopov in globalnih zaklopov.

Kaj so rolo elektronske naoknice?

Rolling shutter kamere so pogostejše pri cenovno ugodnejših amaterskih fotoaparatih in delujejo tako, da skenirajo vrsto fotografij na senzorju od leve proti desni, nato pa se spustijo v naslednjo vrstico in skenirajo od desne proti levi. Vije se od zgornjega levega do spodnjega desnega. Senzor je vklopljen samo za zajem slike v času, ko se ta določen del senzorja skenira. Zato je čas osvetlitve čas, potreben za skeniranje od zgornjega levega do spodnjega desnega dna

While it can take as little as 1/16,000th second for each row to be scanned the total time is close to that of a slow mechanical shutter – between 1/10 second and 1/60 second. This is because it takes a moment for the camera to process the data from the sensor.

Using rolling shutters can be an issue if your subject is fast moving or if you are panning quickly in your shot. It can cause banding or distortions where a subject appears jelly-like because the image has changed between each row of the sensor being scanned.

What is a Global Electronic Shutter?

A global shutter, as the name suggests captures the entire image all at once in a similar way that a mechanical shutter camera does. Sometimes known as e-global shutters, they allow light to hit and be recorded across the entire sensor simultaneously in either a “hard” or “soft” exposure.

A hard shutter exposure works like turning a light switch on and off. The sensor goes from not recording to recording and back again in an instant. A soft shutter exposure, on the other hand, works more like a sunrise and sunset with the sensor being exposed and obstructed more gradually.

Global shutters also require the camera to have a sensor with a very high read speed so that it can process all the data that is being captured. Obviously, this makes using global shutters in cameras with larger sensors more difficult and why they are most common in cine cameras. However, they are becoming more common in mirrorless cameras especially in cameras with M4/3 sensors.

Advantages to Using Electronic Shutters

• They are silent – without the moving parts of a mechanical shutter the camera is silent which is great for wildlife photographers and other situations when you need to not make any noise.
• Faster shutter speeds – electronic shutters eliminate the mechanical shutter delay meaning that a shutter speed of 1/32000 second is not that unusual.
• Higher continuous shooting rates – as the camera doesn’t need to wait for the mirror and shutters to physically reset it can be ready to take the next photo quicker.
• No more blackout – as these cameras use an electronic viewfinder you can continue to see through the viewfinder through the shot which is great for long exposures, panning and continuous shooting.

Disadvantages of Using Electronic Shutters

• Potential for Banding and jelly-like distortion in rolling shutters – this is especially prevalent in fast moving subjects and during panning.
• Flickering light banding – electronic shutters don’t always cope with flickering light sources and often banding can be seen which is difficult to remove.
• Slow flash sync speeds – while you can still sync flashes with cameras using electronic shutters the top sync speed is generally much lower.
• Obstructed use – in some cameras, using the electronic shutter can stop you from using some features of the camera.

What Is an Electronic Front-curtain Shutter?

The electronic front-curtain shutter (EFCS) is becoming a common feature in DSLRs and especially mirrorless cameras. It has been developed as a kind of hybrid of mechanical and electronic shutter action allowing the photographer to overcome particular shutter issues, although it doesn’t eliminate them all.

One of the most common issues with mechanical shutters is shutter shock, or the blurring of an image due to the shake that the first shutter (front-curtain) causes when moving. As the second shutter, or rear curtain, moves at the end of the exposure it doesn’t add to the camera shake. Therefore, if you can find a way to stop the front curtain camera shake you get rid of shutter shock.

This is how EFCS was born. When EFCS is being used the exposure is started electronically and finished using a mechanical shutter. This makes complete sense especially when considering mirrorless cameras and their lack of mirrors.

As I explained earlier, without the mirrorbox, the light is constantly hitting the sensor of a mirrorless camera so it seems a little redundant to have to close a shutter to then have to immediately re-open it again to expose for the image. If nothing else, it wastes time.

However, while EFCS may seem like the shutter saviour it does have a few downsides. For starters because it has to read the whole sensor at the start of the exposure and this takes time, its sometimes not great when you’re shooting fast moving subjects. For this reason, cameras that use EFCS often have limited maximum shutter speed. So, if photographing competitive cyclists or cheaters is your thing a mechanical shutter camera might be a better option. Other downsides such as flickering, and banding are due to the electronic nature of the shutter whereas because of the mechanical rear curtain it will be louder than an electronic shutter.

Which Kind of Shutter Should I Use with My Mirrorless Camera?

A lot of cameras nowadays enable you to decide whether to use a mechanical, electronic or hybrid shutter for capturing your images. Some cameras will even let you leave it up to the cameras microprocessor if you put it into automatic mode. However, if you’re looking to get the most out of your photography having a basic understanding of which types of shutter lend themselves best to which type of photography isn’t going to do you any harm.

Pokrajinska fotografija

A fully electronic shutter setup is a great choice for shooting landscapes. However, if you find that there is quite a lot of artificial light or fast-moving subjects such as wildlife it may be better to switch to a mechanical shutter (or EFCS). As electronic shutters can sometimes prevent certain features such as long exposure noise reduction from being used it may be better to switch to a mechanical shutter in low light conditions

Portrait Photography

Portraiture lends itself to mechanical shutter setups by default. This is especially true if you are using a flash. However, if you are shooting outside and risk overexposure it may be better to switch to an electronic shutter if the shutter speed allows.

Sports, Wildlife and Marco

To avoid rolling shutter issues and eliminate banding opt for mechanical shutter for these kinds of photography.

Documentary Photography

This type of photography works best with electronic shutters as it allows you to shoot silently. However, switching to mechanical shutters may work best if you are indoors.

Cityscape &Architecture

If there is artificial light in your shot, use mechanical shutters.

As technology continues to progress the future may see the need to stop using mechanical shutters in favour of fully electronic. However, at least for now, the advantages of having at least a hybrid system in terms of the quality of the images produced far outweigh not having them.

Learn more about mirrorless cameras and find the right mirrorless camera for you here.