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Most of us either own or have used a D-SLR or use cameras which empower us with the ability to manually make changes to the camera settings, so it’s definitely useful to understand those setting and in time master them, while the “Auto” mode or built in presets could get you good results, learning and understanding how to use the manual functions effectively would yield you even better results and the satisfaction of being able to capture an image just the way you want Let’s try and understand the three main functions Aperture, ISO and Shutter Speed. 1) What is Aperture? Aperture is the opening in the lens through which light passes and enters the body of the camera. The larger the opening the more light gets in and inversely the smaller the opening the less light gets in. Aperture is measured in F-Stops and determines the size of the aperture, for example It’s important to keep in mind that the small number f/1.4 is larger than f/2.8 and much larger than f/5.6. The smaller the f-number the larger the opening the more light enters the camera body. Your probably wondering this is good information but what about implementation, so let’s discuss that. The size of the aperture has a direct impact on the depth of field, which is the area of the image that appears sharp. A small f-number such as f/1.4 (bigger aperture) will isolate the foreground from the background by making the foreground objects sharp and the background blurry, while a large f-number such as f/8.0, (smaller aperture) will bring all foreground and background objects in focus. Every lens has a limit on how large or small the aperture can get. This information is usually printed on the lens itself, for example on my Sony Nex-5 its 3.5-5.6/18-55, where 3.5 is the largest aperture and 5.6 is the smallest. 18-55 is the focal length of the lens (we could discuss the relation between aperture and focal length in another topic) The largest aperture of the lens is much more important than the smallest, because it shows the speed of the lens. Larger maximum aperture means that the lens can pass through more light, and hence, can capture images faster in low-light situations. Examples of apertures that is suitable for the respective kind of photography. Landscape photographers usually use small aperture settings (large f-number) this ensures that from the foreground to the horizon the subject is relatively in focus. Portrait photographers usually use large aperture settings (Small f-number) this insures that the subject is in focus while the rest is blurry, this emphases the subject while blurring and background distractions. Summary: High Aperture - f/2.8 or lower – Shallow depth of field – Ideal for Portraits Low Aperture – f/8.0 or Higher - Extended depth of field – Ideal for Landscape Photography Side note – The lens is sharpest at the centre of the aperture range, for example aperture range of f/1.4, f/2.0, f/2.8,f/4.0,f/5.6, the lens would yield the sharpest image at f/2.8 (other effecting factors - ISO, shutter speed). 2) What is ISO? ISO is the sensitivity of the image sensor to light. The lower the number (e.g. 100,200) the less sensitive the camera is to light but it produces less noise (barely visible) which means high quality pictures. The higher the number (e.g. 12,800,25,600) the more sensitive the camera is to light but it produces more noise and relatively low quality pictures with lot of noise (grains in the photograph) So when would you use a low or a high ISO? Since the lower ISO gives the best image quality we would love to use it all the time, but since the sensitivity of the sensor is relatively low with lower ISO it would make sense to use it in situations where there is ample light available (a bright sunny day, outdoors). However in low light situations (indoors, evenings etc) because there is hardly any light to work with, the ISO would need to be increased so that the sensor can become more sensitive to the available low light and be able to capture the subject, bumping up the ISO enables us to capture images in relatively low light situations but at the expense of introducing noise and reducing the overall quality of photographs. Typical ISO sequence The important thing to understand is that with each stop (e.g. from 100 to 200) the sensitivity of the sensor to light is doubled. So at ISO 12,800 the senor is 8 times as sensitive which means the time required to capture the image is reduced by 8 times. (Higher Shutter Speeds) Summary: As far as possible try to use the lowest ISO to yield the best image quality, try tweaking the Aperture and shutter speed accordingly, increase the ISO has a last resort. Side note – Usually ISO up to the third last stop should yield decent workable photographs e.g. In the above “Typical ISO sequence” ISO up to 3,200 would yield a decent photograph with some noise. (This might be different depending on the camera you use and is subjective to personal preference of image quality) 3) What is Shutter Speed? Shutter Speed is the length of time the camera shutter is left open to allow light to expose the camera sensor. Shutter speed is measured in seconds or fraction of seconds where 1/250 is faster than 1/15 while 1” is much slower then both. Seconds are usually denoted by the symbol “. Higher Shutter speeds are ideal for capturing still images of “motion” for example 1/500 would be fast enough to capture still images of most humans in action. While a Slow shutter speed of 1” would create a blurring effect, it would make flowing water look like milk. Some cameras also have a “bulb” mode where the shutter is left open for has long as you keep the shutter button pressed this mode makes for some interesting light painting photographs. While choosing the shutter speed it’s important to know that anything slower that 1/60 would introduce blur in your photographs due to hand shake. The immediate solution would be to use a Tripod of use a lens or camera with image stabilization. The safe shutter speed for hand-holding the camera would be to choose a shutter speed with a denominator that is larger than the focal length of the lens. For example if you use a lens with a focal length of 55 mm a shutter speed of 1/60, 1/125 or higher would be ideal. Summary: Higher shutter speeds 1/250 and above are ideal for capturing still pictures of motion (humans, birds, objects etc) Shutter speeds between 1/125 and 1/60 would best for capturing regular human movement and would not require a tripod. Slower shutter speeds of 1/15 and below would introduce motion blur and would require a tripod. Side note – When the shutter speed is changed, you would also need to pay attention to the Aperture and ISO. Let’s say the shutter speed is changed from 1/60 to 1/125 this would result in half has much light entering the camera, so to compensate you would either need to increase the ISO (e.g. from 100 to 200) or increase the Aperture Summary - Aperture, ISO and Shutter Speed Changing Aperture changes depth of field. Changing ISO changes the image noise Changing Shutter Speed changes how motion is captured Taking a Great picture is a balancing act between these three elements of photography. The best way to learn and get better at photography would be to master the basics and then combine that knowledge with your Artistic side. Just keep on exploring the world around you and your camera and take great pictures J
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Rukovanje fotoaparatom EKSPOZICIJSKI TROKUT: f-BROJ, BRZINA ZATVARAČA, ISO Pri fotografiranju je potrebno uskladiti tri međusobno povezana čimbenika ekspozicije. Ekspozicija je izloženost svjetlosnog senzora svjetlu. Ekspozicija će ovisiti o f-broju, tj. o otvorenosti objektiva (količini svjetlosti koju propušta objektiv ), o vremenu osvjetljavanja senzora (to vrijeme određuje zatvarač, tj. koliko je dugo otvoren) i o ISO vrijednosti (osjetljivosti senzora na svjetlo). Kad naučimo usklađivati ta tri čimbenika, spremni smo napraviti tehnički dobru fotografiju (osvijetljenu upravo onoliko koliko je to potrebno). f-BROJ (otvor blende) F-broj je vrijednost otvora blende (otvorenosti objektiva) i to je brojčana vrijednost koja po standardima udvostručuje količinu propuštene svjetlosti: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16 i f/22, a može biti izražena i u raznim međukoracima: f/1.2, f/1.4, f/1.6, f/1.8, f/2, f/2.2, f/2.5, f/3.2, f/3.5, f/2.8, f/4, f/4.5, f/5, f/5.6, f/6.3, f/7.1, f/8, f/9, f/10, f/11, f/13, f/14, f/16, f/18, f/20, f/22, f/32. Otvor blende možemo kontrolirati na fotoaparatu. Dakle, fotograf sam određuje koliko će objektiv biti otvoren ili zatvoren za prolazak svjetlosti. Otvor blende (f-broj) je omjer žarišne duljine objektiva i promjera otvora objektiva. Što je f-broj manji to je otvor objektiva veći (blenda je veća). Svaki objektiv na sebi ima oznaku najveće moguće otvorenosti blende (1:4 – znači da se može otvoriti do f-broja f/4; 1:5.6 – znači da se može otvoriti do f-broja f/5.6). Objektivi s otvorom blende 1:1.2, 1:1.4, 1:2.8 svjetlosno su jaki i zbog toga su skuplji od objektiva s otvorom blende 1:4, 1:5.6 i sl. Svjetlosno jaki objektivi nazivaju se i „brzim objektivima“ jer je pomoću njih moguće povećati brzinu zatvarača i dobiti bolju fotografiju. Što to sve kontroliramo f-brojem? Dvije su osnovne stvari: količinu svjetla koja dolazi do svjetlosnog senzora i polje dubinske oštrine. Otvaranjem blende dovodimo više svjetla do senzora, dakle – brzina zatvarača bit će veća. Zatvaranjem blende do svjetlosnog senzora dovodimo manje svjetla, dakle – bit će nam potrebna manja brzina zatvarača. Uz to moramo istovremeno i kontrolirati osjetljivost senzora (ISO vrijednost). Na manje osjetljiv senzor morat ćemo „poslati“ više svjetla, a na osjetljiviji senzor manje svjetla. Navedeni tekst ulomak je poglavlja „4. Rukovanje fotoaparatom“ iz knjige „Promišljati fotografski“ autora Davora Žerjava. U 4. se poglavlju obrađuju teme: Držanje fotoaparata, Ekspozicijski trokut, f-broj (otvor blende), Brzina zatvarača, ISO (osjetljivost senzora na svjetlo), Fokusiranje centralnom točkom, WB (white balance, ravnoteža bijele boje), Korištenje histograma, RAW i JPEG. Impresum, sadržaj kao i neke od stranica knjige možete pogledati ovdje. Specifikacije: Cijena: 150 kn Format: 21 x 20 cm Broj stranica: 224, boja Uvez: meki Godina izdanja: 2011. Izdavač: Fotoklub Čakovec