Exposure And It’s Mythical Triangle!

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No matter where on the web you look as a photographer you will come across the mythical “Exposure Triangle”, some are simple and leave you guessing as to what they mean, some are packed with so much information they are next to useless. In this article you won’t find one. In my view the only reason people create these graphic is because exposure is controlled by three parameters and that fits nicely into a triangle; either that of they do it just because every one else does!

The three things that control exposure are the sensitivity of the sensor or film (ISO), the aperture that regulates how much light gets in (f-stop), and how long light is allowed onto the sensor/film (shutter speed). As there are three things involved and each of the three has it’s own property it means there is no one correct exposure for a scene, just the one that suits what you are trying to achieve. Below is my “Sunny 16” table, as a child I was told that on a bright summers day the correct exposure was ISO 100, 1/125 of a second at f/16. This was great as I got nice bright images with most things in focus and not too much blur, and my love of photography was born. In this table all the combinations shown will result in the same exposure but with subtle differences based on the properties of the three elements of exposure."Sunny 16" Exposure Table

1. Sensitivity or ISO

This is the one that some think has no side-effect, just push it up high and you will get sharp pictures. Well bush it up too high and that is exactly what you won’t get! ISO is a measure of just how much light is needed to form an image on the digital sensor of film in your camera. Lower ISO means you will need more light or more time to form the image, low ISO images tend to be crisper. On film this is because the light-sensitive grain of the photographic emulsion is finer, in digital cameras it is because of electronic signal noise; which was an effect similar to grain.  Grain/noise is not always bad as it can bu used to create atmosphere, but on the whole I try and avoid it where ever possible.

Low ISO = Low digital noise fine grain, more fine detail.

High ISO = Increased digital noise, or coarser grain, less fine detail.

2.  Aperture or F-Stop

This is the one with the most noticeable effect it controls how much of your image is in focus, this is the depth-of-field. The lower the number the more light is let into the camera so the exposure time can be shorter, the downside is that the depth-of-field becomes narrower and focus more critical. The higher the number has the opposite effect, less light but more of the image is in focus. It may seem odd that the bigger the number the smaller the aperture and the less light is allowed through, but it’s quite simple really f/2 means the aperture diameter is half the focal length, so for a 50mm that’s 25mm, and f/16 has a aperture of only 3.125 mm in diameter.

Low F-Stop = More light, shorter exposure less in focus.

High F-Stop = Less light, longer exposure more in focus.

3.  Shutter Speed

This is simplest one to understand. This is the setting that stops the action, or adds “artistic blur”. Shutter speed is generally measured in fractions of a second, but can be seconds or minutes for night time or low light photography. But such long exposures have their own set of rules which I won’t bore you with here.

Low (Slow) Shutter Speed = More light, more chance of motion blur.

High (Fast) Shutter Speed = Less light, stops the action, less blur.

So as with most things it’s a trade off. If you take the benefit from adjusting one of these three, you have to consider the effects caused by the changes to the other two; if you want to stop the action you increase the shutter speed, but then you either have to open the aperture and less is in focus, or increase the ISO and risk introducing noise or grain. Should yo want a wonderful landscape, then the depth of field (how mush is in focus) and detail will be what you want will be key, so you will probably need a tripod to deal with the low shutter speeds. There is no correct answer to this, the correct exposure is the one that gives you the image you are trying to achieve.

I hope this has helped a little, it’s not an easy thing to grasp, but it is key to good photography. So go out turn off your cameras automation and give it a go. You may well be pleased with the results.

Wildlife Photography With Camera Traps

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Camera Traps; I’m sure if you watch the BBC’s Springwatch program, or any recent wildlife program you will have a good idea what they are. On TV it’s a box that a presenter or wildlife cameraman straps to a tree, goes to bed then returns the next morning to find it full of wonderful images. Well my experience suggests it’s not quite like that!

Why is in not that easy, well it is highly probable program in question will place multiples of these traps in areas where researchers taken days possibly weeks trying to predict they are most likely to get the images they are after. For me and most “home based” amateur photographers multiple traps and a team of researchers are nothing more than a dream! The reality for me (and possibly most of you reading this) is one camera trap and no research team because that’s what is affordable/justifiable. Given this to be the case there is a need to make the most of the investment in this piece of kit. As with most things to get the best performance out of a Camera Trap you will need to be familiar with it and how it works, and be aware what it will and will not do. My first suggestion is put some batteries into the camera-trap and put it out in your garden to see how it performs, you may only photograph the neighbours cat on a midnight patrol but you will get some experience of using and placing the Camera Trap to best advantage. The first time I did this I found out two things, firstly that the default sensitivity of the motion detector (PIR – Passive Infra-Red in my case) is way too high in the winter months, secondly that I have frogs in the garden even though the nearest stream/pond is quite a fair way off.

Typical Wildlife Camera TrapNow the devices it’s self, well these devices range from not too expensive to very expensive. My advice is to work out what you need (not want) then shop around, there can be some good deals to be had on Ebay, but be sure know how much these things are retail before you enter into a bidding war. Consider the resolution you need, does the camera support infra-red for low-light/night photography. Do you need video? What is the trigger time (time from tripping the sensor to taking the image), cheaper devices can have trigger times in excess of two seconds, an animal can move a fair distance in that time. Does the camera have a backup battery set, or the ability to be powered from an external battery pack. There are lot’s of options to consider, but watch the price when adding anything more than the essentials,  you may find that adding just one more thing to the specification can make a big difference to the price you may expect to pay.

My Tips:

1. Know your camera how it works and how it reacts (use the garden test until you are really comfortable using it).

2. Research your target animal, this is one of the best things you can do you improve your chances of getting the images you want. If you know something of how your chosen animal behaves, what times of day it is active, and it’s preferred habitat you are half way there.

3. Research your location before you pace your camera trap, pre-visit the site/sites beforehand and look for signs that the animal you are after is there, take a notebook a good map and or/GPS, mark the location of animal signs and possible camera trap locations.

4. Pick locations away from well trodden paths; your chosen animal is more likely to show up, and you camera stands a better chance of still being there when you go to retrieve it.

5. When going out on a field trip load it with new or fully charged batteries, then put a spare set in your bag. There is nothing worse than getting to the trap site and realising you actually forgot to put batteries in your camera trap. Also take a spare memory card, you may have forgotten to put one in, or the one in the camera could fail.

6. When placing your camera trap, don’t break any laws such as trespass, and if you are working in a habitat that supports an endangered or at risk species take care not to disrupt it’s habitat or environment.

7. When placing you camera face it across the target area for side on shots or pointing down the trail for head/tail (you don’t know which way the animal will be travelling) shots.

8. Take into account the size of your quarry when placing your camera, if it’s fairly small ground dwelling then site it low down. If you are not sure then mounting the camera-trap between 30 and 60cm off of the ground is a fairly safe bet.

9. Beware of the direction of the sun at sunrise and sunset, a lot of animals are most active during these periods, and the last thing you want is that perfect shot being ruined by rays from the rising or setting sun shining directly into you camera. I always try to place my camera facing either north or south to avoid this issue (this is where a compass comes in handy).

10. Before mounting the camera-trap into position do some final checks; make sure it’s turned on. Check the time and date is set correctly if you are going to time stamp your images. Format the memory card to ensure you can store ans many images as possible, and that it is OK. Check the battery status of the camera.

11. Security lock the casing closed if your model supporters this, then lock it into position where at all possible, I tend to use a bicycle cable lock as well as the straps to mount my camera trap.

12. Scent! To most animals we humans must seem incredibly smelly, and human scent is the last thing you need on your equipment so:

  • Keep your camera outside if at all possible so not to pick up household smells; not the garage or shed as those places are often full of other odour’s that can cling to your camera.
  • If you keep the camera-trap indoors, as soon you have a plan to use the camera-trap leave it outside to de-sent the camera (a week or two should do the job, especially if it rains).
  • Carry the camera to site on the outside of your kit-bag, this will stop it picking up new scents from sandwiches and waterproof clothing, it will also allow the wind and the trail more time to de-scent your equipment.
  • Once at the chosen location keep you handling of the camera-trap to a minimum.

13. Use local vegetation to increase your camera-trap’s camouflage, if it’s less visible to animals it’s less visible to thieves.

14. Make a note of the grid reference and make notes as to where the camera-trap has been placed, the human memory is a wonderful thing but it’s not infallible! If you have another camera with you take a snap of the camera-trap in place as a reminder.

Thats about it for this  the first post on the new site, I hope you found it both useful and informative.

New Year New Site!

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With 2012 just a few days away, I reviewed my site and what I wanted to do with it. My decision was to increase the “blogging” content along site being more active with photographic postings.  While the album side of the previous site was quite good the blogging side was poor.   So bye-bye popular CMS website, welcome WordPress.

Changing software is a massive step for this site, so while I intend to “go-live” on January first, it may take a week or two, or three for me to sort it all out to how I want it; so please bear with me.

Rob.