The exposure triangle and wildlife/bird photography

I received a question from a friend regarding the high ISO I am using in my wildlife and/or bird photography. So I decided to write a short post on the exposure triangle to explain the concepts I am using and hopefully it will explain why I do some an ISO for certain photos.

1.         Exposure triangle

I do use the well-known exposure triangle when I consider taking a wildlife/bird photo. The three main controls for adjusting the amount of light (exposure) in any images are:

  • Shutter Speed
  • Aperture
  • ISO

As you can see, Shutter Speed is one of the three pillars of photography, the other two being ISO and Aperture. Shutter speed is where the other side of the magic happens – it is responsible for creating dramatic effects by either freezing action or blurring motion. Therefore, it is important to decide beforehand what your aim with a photo is:

  • Will it be a record photo and/or a stationary bird?
  • Will it be a bird in flight?
  • How much blur do want in your photo?

2.         Aperture mode

But let us take a step back. First, you need to decide which camera mode/priority you want to use when shooting wildlife/birds. When I started taking photos about 3 years ago with a bridge camera, I’ve only used the “Automatic” mode/priority because I did not understand the other settings. Automatic means the camera itself decides which shutter speed, ISO and aperture are the best for the conditions/the specific photo you want to take. The Automatic mode is great for beginner but not if you want to play around with the photo.

Nowadays I do use the Aperture mode of my camera most of the time when shooting wildlife/birds as are many other great photographers (Manual for landscapes). It is very helpful especially if the action is fast and one needs fast re-actions/reflexes.  All it means is, when I shoot in Aperture mode/priority, the first thing you need to decide/set is the lens aperture and it will depends on what I want to photograph. Then the camera automatically sets the shutter speed. In Aperture mode, I cannot directly set the shutter speed. But what does it mean if I am setting the camera’s Aperture first?

Remember that Aperture is one of the three pillars of photography and of the exposure triangle. Therefore, exposure is one the main issues to consider when it comes to wildlife/birds photography.

Let us get back to Aperture. The aperture of a camera (how big or small the lens diaphragm inside a lens opens up) allows different amount of light to fall onto the sensor of your camera. Aperture adds a dimension to a photo as it determines the area which will be in focus (the depth of field) for example the aperture can be used to blurring the background behind your primary object (e.g. at f2.8) – the bird  or it can bring everything in focus (e.g. f16).

To summarise; 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 opening is reflected in a large f-number for example f22, (called a small aperture) and it will bring all foreground and background around objects in focus. I do use such f-stops in landscape photography.
  • A large opening is reflected in a small f-number.  A small f-number for example f4 (called a large aperture) will isolate the foreground with your object (the bird) from the background by making the foreground and object look sharp while the background will look blurry. When we consider exposure and Aperture, larger aperture means that the lens can pass through more light, and hence, your camera can capture images faster in low-light situations. Having a larger maximum aperture also means better ability to isolate subjects from the background.

An easy way to remember the Aperture function:

  •  Small opening – big number – small/narrow depth of field (Small-big-small)
  • Big opening – small number – big/wide depth of field (Big-small-big)

3.         Shutter speed

The next pillar to consider is the shutter speed but I am not going into the detail of the shutter speed. Only the fact that if you want to freeze all the movements/actions, you need a fast shutter speed (e.g. 1/1000 sec) and if you want a blurry effect, you need a slow shutter speed (1/30 sec).

Just the following piece of advice regarding shutter speed:

  • Looking at shutter speed in isolation from the other two pillars of the exposure triangle (aperture and ISO) is not really such a good practice. Once you decide on a specific shutter speed or if you want to change the shutter speed, you’ll need to change one or both of the other pillars to compensate for the change in shutter speed but still get a well-exposed photo. For example if you change your shutter speed one stop (for example from 1/125 sec to 1/250 sec) you’re effectively letting half as much light into your camera. To compensate for less light coming into the camera you’ll probably need to increase your aperture one stop (for example from f16 to f11).
  • Focal Length and Shutter Speed – as a side line – another issue to consider when choosing shutter speed is the focal length of the lens you’re using (e.g. 20mm lens). Longer focal lengths will accentuate the amount of camera shake you have and so you’ll need to choose a faster shutter speed (unless you have image stabilization in your lens or camera). The ‘rule’ of thumb (to use with a lens of a specific focal length if no image stabilized system is used) is to choose a shutter speed with a denominator that is larger than the actual focal length of the lens. For example if you have a lens that is 200mm, shutter speed of 1/250th would be acceptable but not a shutter speed of 1/60sec.

To summarise the issue of the shutter speed:

  • You need to develop your own style of photography.  The two major determining factors assisting you to make a decision on the shutter speed are (a) your style of photography, and (b) what you wish to photograph.
  • Looking at the above-mentioned two pillars, it is acceptable to assume that both the aperture and shutter speed control the amount of light that reaches the sensor of a camera. Therefore, there is a very strong relationship between the two pillars. So, with aperture and shutter speed, the objective is to control and regulate light reaching the camera’s sensor in order to have a proper exposed photo.

4.         ISO

Therefore, as the name suggets – there should be a third pillar in the triangle. Just to complicate matter? No not really as it is not so complicated if you do understand all the pillars and go out to practice a lot. Now, not to confuse you – let us rather go back to the exposure triangle and complete the third pillar of the exposure triangle namely ISO.

ISO is the measure of a digital camera sensor’s sensitivity to light. With aperture and shutter speed, one can control and regulate the light coming through the lens to the camera but the sensor’s sensitivity for the light can vary.

Let us look at the following scenario (in bird photography) and apply the principles discussed above:

  • Say for example you saw a large raptor sitting on a bush and you’ve decided that you want to us an f-stop of 5.6 in order to get the entire bird in focus – especially if it is a large raptor. An f-stop of f2.8 will probably blur the wings (what we call “soft wings”) of the raptor if you are too close to the bird. You decided that you want to catch the bird in its take-off (BIF = bird in flight) and for that you need a fast shutter speed (e.g. 1.3200sec). Such a fast shutter speed will freeze the moving wings and other actions of a large raptor in flight. Also, it is very late in the afternoon and there isn’t much light left.

The implications of your decisions/settings:

  • A fast shutter speed (1/3200sec) is letting in less light (and already there isn’t that much light available) and therefore, your photo will be underexposed and you might get clipping of the darker areas with the loss of detail in that areas on the bird. And that is a “total no-no” in wildlife photography.
  • Therefore, you need to compensate in order to get more light to the sensor of the camera and get a well-exposed photo.
  • One way to compensate is to increase the aperture (bigger lens diaphragm opening = smaller f number = f2.8) and that will allow more light to reach the sensor.
  • In Aperture mode, if you increase your f-stop van f5.6 to f2.8, your shutter speed will be changed from 1/2000 to 1/3200 – the desirable effect. BUT (and it is a major BUT) the larger aperture will result in the creation of a less depth of field and the wings of the raptor will be out of focus. And that is not what you want. And that is where the third pillar namely ISO comes into play.

The higher you set the ISO of your camera, the more sensitive is the sensor for light meaning less light is necessary to capture a well exposed image. So, ISO200 is twice more sensitive than ISO100, while ISO 400 is twice more sensitive than ISO200. This makes ISO 400 four times more sensitive to light than ISO100, and ISO1600 sixteen times more sensitive to light than ISO 100, so on and so forth. What does it mean when a sensor is sixteen times more sensitive to light? It means that it needs sixteen times less time to capture an image! Look at the scenario below:

ISO         –    shutter speed example:
ISO100      – 1/400 of a second
ISO200     –1/800 of a second
ISO400     – 1/1600 of a second
ISO800     – 1/2000 of a second
ISO1600   – 1/3200 of a second
ISO3200  – 1/4000 of a second

In the above scenario, you’ve set your camera in Aperture mode and decided to use an Aperture of f5.6 for your shot. Your camera sensor needs exactly 1/400 of a second to capture a well exposed image at ISO100 for/at that f-stop (f5.6). But you need a shutter speed of 1/3200 sec for your shot to freeze the movements. Now, by simply switching the ISO from 100 to an ISO of 1600 (and keeping the aperture (field of depths already determined) at f5.6), you can get the desired shutter speed of 1/3200 of a second and you can capture the same scene at the desired shutter speed (1/3200 of a second) to freeze the movements/actions and keeping the depth of field at the desirable level.

To summarise – when to increase the ISO on your camera:

You should increase the ISO when there is not enough light coming through for the camera to the sensor as you have already a pre-determined aperture (field of depth) and shutter speed (to freeze the movements). But before increasing the ISO, you should think about your ISO level as the increased ISO levels will introduce noise to our photo. Once again you can the question: “Why not keep the ISO at 400 or 800 all of the time? Just remember, the lower the ISO, the better the quality of the photo. That is why I usually try to shoot at the lowest possible ISO.

5.         Exposure compensation factor

In order to shoot at the lowest possible ISO, I also use the Exposure compensation factor. When shooting in the Aperture mode, one can increase the Exposure compensation factor (the + or – setting) on your camera as a fourth possibility to get a well-exposed photo.

Once I’ve decided on my Aperture (e.g.f5.6) and my desired ISO level (e.g.800) and I know I want a shutter speed of 1/3200sec, I set my camera on Aperture priority, set my Aperture at f5.6, set my ISO at 800 and then I use the Exposure compensation to get the predetermined shutter speed of 1/3200.

6.         Summary

To summarise:

First I need to decide what kind of photograph I want to take:

  • Do I want to freeze the action – high shutter speed (e.g. 1.3200sec)
  • Do want a blurry effect – slow shutter speed (1/30sec)
  • What is the quality of the light in the environment/surroundings? (use all three pillars of the exposure triangle to get the best possible shot (quality-wise).

Please read my other blog on wildlife and bird photography tips:

http://willemkrugerphotodiscuss.wordpress.com/

Any comments are more than welcome but rather keep on shooting until you’ve developed your own style.

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  1. #1 by Sandra Grobler on September 27, 2012 - 6:24 am

    Dankie Willem – dis hoe ek dit nou verstaan:
    1. kamera op aperture
    2. besluit oor 5.6 / 8 /11 ens – so kom ons sê ek kies nou 5.6
    3. besluit oor vries of blur – vries = vinnige shutter en blur = stadige shutter
    4. ek kies vries dus moet dit vinnige shutter wees
    5. om vinniger shutter te kry as wat die kamera gekies het moet ek ISO opstoot
    6. omdat ISO noise veroorsaak kies ek “veilige” ISO setting en verhoog exposure.
    7. F5.6 / 1.3200sec/ISO 800 / + 1 – dit sal dan min of meer so iets wees?
    8. dus eintlik 4 faktore wat saam werk?

    ek het ongelukkig nie nou my kamera by my nie – gaan dit eers vanmiddag oefen – AS EK NET ‘N VOëL kan kry wat wil saam oefen!!!

    Ek het nog baie vra oor hierdie onderwerp waar wil eers bietjie gaan rondspeel en oefen met die settings soos jy dit nou verduidelik het.

    En aangesien ek eintlik meer belang stel in landskap fotografie wil ek baie graag weet hoekom jy Manual gebruik – maar ons praat later daaroor.

    Dankie vir jou tyd en moeite .

  2. #2 by whk139 on October 1, 2012 - 2:52 pm

    Hi Sandra – bullet 1-8 is perfek.

    Addisioneel: Wat ek aanbeveel is dat jy ‘n default setting vir wildsfototgrafie op jou kamera hou – soos byvoorbeeld Aperture mode, f5.6, ISO400 en exposure compensation van -0.33 (my default settings). ‘n Fasiliteerder op een van ons wildsfotografie werkswinkels het dit vir ons voorgestel en gesê dat jy nie sommer ‘n fout sal maak indien jy vinnig na jou kamera moet gryp en nie tyd het om stellings te verander nie. Na elke skoot/foto geleentheid moet jy jou kamera terugstel na die default setting voordat jy jou kamera neersit en verder ry, net om weer na die volgende skoot te gaan soek. Dit verg nogal baie selfbeheersing en commitment, maar dit is ‘n goeie gewoonte. Dit sal keer dat jy nie die volgende skoot (wat dalk in die skaduwee is en die vorige skoot was in helder sonlig) opmors indien daar nie tyd is om oor jou stellings te dink nie. EN dit gebeur – glo vir my.

    Yes, nou moet jy gaan oefen, oefen en nogmaals oefen. Maar laat weet hoe dit gaan.

    Laat waai met die vrae

    Landskappe – perd van ‘n ander kleur, maar net so lekker. Google ‘n bietjie Hougaard Malan en sy blog ook. Ons was saam met hom Namibie toe – baie geleer.

  3. #3 by Sandra Grobler on October 3, 2012 - 5:57 am

    Ja ek het al Hougaard gaan besoek – eendag as my skip kom! Ek hou weer my kamera op F8 – maar dis maar al – geen ander settings nie – dus gebruik ek of 8 / 11 of 5.6 en laat die kamera maar die res doen. As dit bietjie bewolk is verhoog ek die ISO (hou dit gewoonlik op 200) – maar ja dan gebeur presies wat jy sê – kom in helder sonskyn en my ISO is te hoog. Ek het ‘n oulike video clip gesien. Die vrou sê as jy aan een van die driehoeke skuif moet jy die ander oof skuif om weer dieselfde perfekte driehoek te kry (weet nie of jy my nou verstaan nie) Maar waar begin ek? Ek het ook gelees van die perfekte16 op ‘n helder sonskyn dag – ek dink dis F16 1″ iso200 – nou soos ek haar verstaan as ek F16 na F8 gaan is dit mos F16 F11 F8 – dus 2 skuiwe . Nou moet ek of die shutter of die iso ook twee keer aanskuif. So ek gaan my kamera stel soos joune en kyk hoe dit lyk – dan as ek die apature van 5.6 skuif na F16 is dit drie skuiwe – so iets moet drie keer geskuif word – ek sou sê nie die iso nie want dit is reeds op 400 so dan moet dit die shutter wees – maar die kamera kies op apature self nie shutter spoed – reg? of rol ek nou toetaal van die berg af? Ek dink ek is besig om myself so deurmekaar te maak. En dan sommer nog iets asb – as die histogram meestal na regs of meestal na links wys – met wat verander ek dit sodat dit korrek is – die exposure compensation? Jou landskap fotos is stunning! Ek sal wat wil gee vir so kursus en sulke foto geleenthede – maar ek is al klaar baie ddankbaar dat ek ten minste ‘n kamrea het en vriende wat bereid is om hulle kennis te deel. Ek dink ek het dit al genoem dat ek op ‘n kursus was maar het nie veel geleer nie – en ek weet ek het nodig om saam met iemand die praktiese oefening daar buite te gaan doen. Ag en nog een laaste vragie net uit naskuurigheid. Hoe neem jy dan nou die voel af – ek bedoelgebruik ‘n soort panning metode? Jy kan tog nie jou kamera op een plek fokus en hoop die voel vlieg voor jou lens verby nie? Vertel so bietjie waar jy gestaan het waar die voel was ens – asb? Dis baie interressant. Ek gaan nou eers weer jou hele artikel oorlees – ek kan nie soveel inligting met eenkeer se lees in neem nie – gesels weer later – en dankie!

  4. #4 by whk139 on October 5, 2012 - 6:44 am

    Hi Sandra – jou laaste comment is sommer ‘n mondvol, maar ek hou daarvan. Dit wys vir my jy is ernstig oor fotografie (net soos ek) en dink oor al die beginsels. Uitstekend. Wat ek nou sal voorstel is dat jy sommer buite gaan staan en oefen op enige voorwerp/landskap. Speel ‘n bietjie rond met die stellings op jou kamera (in Aperture mode) en kyk wat gebeur. Dit is die beste manier om te leer. Miskien gaan die oefening sommer baie van jou vrae beantwoord. Indien nie, laat weet hoe dit gegaan het en wat jy gedoen het ne hoe die fotos uitgekom het. Dan gesels ons weer.

    Yes, daar is baie benaderings tot hierdie beginsels van die exposure triangle. Dit is goed om so wyd as moontlik te lees, MAAR (1) jy moet verstaan wat jy lees en (2) uitgaan en dit prakties gaan toepas om resultate te kan sien.

    Thanks vir die kompliment, maar dit was harde werk. Dit kom nie net sommer van self nie. Ook is goeie mentorskap van uiterste belang (soos jy self uitgevind het – nie alle kursussse leer jou iets nie). EK en my vrou is/was baie gelukkig met uitstekende mentors wat ons gebruik. ‘n Kamera/foto klub is ook ‘n uitstekende leer geleentheid alhoewel die judges se kritiek nogal skerp kan wees (sny somtyds nogal diep dat die bloed loop). Ook het ons ‘n fotografie groepie wat maandeliks bymekaar kom en ons fotos bespreek. Help baie.

    Daar is verskillende manier om die voël af te neem en yes, panning is een manier. Ek sal ‘n volgende post daaroor skryf.

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