Getting off Auto

After reading of a Minsmere volunteer’s walkabout with another guide learning about their camera and getting off the Auto setting, I found myself thinking the answers weren’t quite as simple as perhaps people think.  So I thought it might be interesting to talk a little bit about cameras and the various modes.    Besides, it's been a while since we had a techie conversation so I thought I'd let free my inner geek :-)  I use Canon kit, so will tend to use Canon terms, but the principles apply whatever camera you’re using.

The most basic setting on a DSLR (and I’m talking DSLR, again, because that’s what I’m using) is the full Auto mode (the “green box” on a Canon).  Avoid this one like the plague, it leaves absolutely everything up to the camera, including whether or not to use the flash.  Since the pop-up flash built into a camera is a pretty weak beast, only really designed for use over short distances and with “normal” lenses, it won’t help a bit for most telephoto photography out of a hide.  It’ll also annoy other hide users :-)  Exposure compensation isn’t available in this mode either, so it’s very limiting.

P (or Program) is the mode to use if you want the benefits of full auto but with some measure of control.  The camera chooses the aperture and shutter speed that it feels is the best compromise, based on the lens.  It will automatically give you higher shutter speeds for longer lenses (which is important), but will allow you to “shift” the programme as well, giving you some creative control (ie you may be happy to drop the shutter speed to get a smaller aperture and greater depth of field).  Crucially, exposure compensation is available in this mode as well and that’s something particularly useful with birds in flight (where you can end up with silhouettes against a perfectly exposed sky if you’re not careful).  You can also fix the ISO if you wish in P mode, although in general I’d suggest leaving it in Auto unless you’re particularly fussy, modern cameras handle high ISOs well and you’re better off getting used to everything else on the camera before getting too hung up on ISO.

Once you get away from the relatively simple world of green box and P, you enter the murky world of Shutter Priority (Tv) and Aperture Priority (Av).  Actually, these are still automatic modes, but you get the chance to specifically choose shutter speed or aperture, the camera working out what the corresponding other settings should be to get a perfectly exposed shot.  So when do you use which mode?  Entirely up to you.  There’s no correct answer, like much in photography, but Canon give you the options, so it’s worth thinking about which mode is the most suitable before you take a picture.

Many photographers will swear by Av – controlling the aperture, and hence the depth of field (DoF - how much of the picture is in focus) is the most important thing they will tell you.  Well, let’s be contentious.  Nope, frequently that’s nonsense when you’re pointing the lens at a bird, especially if you’ve spent the money on some high quality glass.  To understand why, you need to understand exactly WHAT DoF you’re going to get when you press the shutter button.  The DoF depends on a number of things, principally the sensor size, lens focal length, aperture and distance to the subject.  If you take that staple of birding lenses, the 400mm, on a crop sensor camera like the Canon 7D at a distance of 30ft (which is pretty close when you’re in a hide) you get a depth of field, wide open f/5.6, of just over 4 inches.  I’ve checked some pictures I’ve taken of a kingfisher and the exif tells me they’re at more like 60ft, giving a DoF of over 8 inches.  That’s more than enough to get a kingfisher in focus.  That 8” DoF may be problematic if you get a Marsh Harrier flying past, but guess what?  They’re normally out at 150ft or more, giving you a DoF around the 10ft mark (according to exif on my own pictures).

So why use Av?  Well, it does let you control the DoF, so any bird that is coming in close, especially if large, you’ll benefit from that control of the in-focus areas.  It’s also a good idea to close down the aperture of a lens a stop or so if possible as that will sharpen up the image you get (it benefits all lenses, but particularly ones at the budget end of the market).  Macro or close up shots will definitely need Av as the DoF can end up being a mm or two which is not very helpful.

A lot of the time however, you may find that Tv, shutter priority, is a more useful mode to use for birds – especially those in flight.  Holding a long telephoto lens still is difficult and camera shake is your enemy.  Stabilised lenses can help (IS in Canon-speak) but IS is useless for in-flight shots as you’re waving the camera around deliberately.  The only thing that will freeze the movement (of you and the bird) is a high shutter speed.  There’s a rule of thumb that says you should aim for 1/focal length, but that’s from the world of film (or full frame digital), so using a crop sensor camera, you should use 1/(focal length x crop multiplier).  Example, for that 400mm lens, on full frame, 1/400^th sec is a good starting point, but on a crop sensor (like the 7D), aim for 1/400x1.6 or 1/640^th sec as a minimum.  That’s for stationary stuff – for in-flight, go higher.  Yes, you may end up with a high-ISO shot, but noise can be dealt with, a blurred pic can’t be saved.

Finally there’s Manual.  That allows you to set both aperture and shutter speed yourself as you’d expect.  Purists will tell you to use this and learn how to use the camera “properly” but personally I don’t buy that.  Learn with whatever modes give you the most satisfaction, you’re meant to enjoy the photography, not find it a chore.  One place I do find manual useful – if I want to stop the lens down a little for sharpness AND maintain control over shutter speed as I’m after in-flight shots, I’ll often use manual with auto-ISO (yes, I know that sounds counter-intuitive).

I’ve realised this has ended up being rather a long waffle, so we’ll leave it there for now!