450D - wildlife, shutter/aperture, zoom and exposure....

Joined: 27 Oct 2006 Posts: 20 Location: Blackpool UK

I've had my 450D for a few weeks now, and have just had the chance to give it a good test out in the New Forest on various wildlife subjects. I have a few questions which I'm hoping you can answer, feel free to answer any or all of these questions, any help would be great.

1, my first question regarding zoom for accurate focus. I was once told that you could get a more accurate focus by zooming in on your subject when you focus, and then reducing the zoom for the shot. My issue with this is firstly... if you do not let the camera take the exposre again at the reduced zoom setting then you'll have an incorrect exposure... however try this, and you'll focus again defeating the point in the first place (unless you start knocking the focus onto manual.... then the whole thing becomes pointless (I'm not aware of any setting where the exposure is constrantly tracking... unless in the sport mode if it does this each time it re-focuses ?) - maybe I should give up and accept the focus I'm offered at the time, and avoid zooming in !

2, Whilst I understand the basics of photography, and have a simple understanding of the camera's instructions, I couldn't find a setting that would have the camera set the fastest possible shutter speed for each situation. I wanted (whilst shooting wildlife with a long lens) to be able to just shoot away knowing that the camera was doing it's best to avoid shake. It was suggsted to me to set Av to its widest setting, getting the most light into the camera and therefore forcing the fastest shutter speed, is this correct ?

3, This question relates slightly to question one, if I'm presented by, lets say a horse or a deer which is side on to me, if I focus on the eyes and therefore set the exposure, how am I sure that when I swing the camera back around to include more of the background that the exposure will be correct, as, if I hold the shutter button half way to keep the focus, the exposure is going to stay locked too ?

If you can offer me any more advice for shooting wilklife with the 450D I'd be very keen to learn

many thanks for reading and for your help !

Paul

Joined: 21 Oct 2006 Posts: 350 Location: Ontario, Canada

1. To focus and change the zoom without changing focus a "parfocal" lens is required. If your lens changes apperture when zooming from wide to narrow, most likely the lens is not parfocal.

2. Using Av set to its wide aperture will indeed set the shutter speed to the fastest available for a proper exposure. If you require a specific shutter speed to stop camera shake and subject motion, set the camera to TV and set the appropriate shutter speed. If the scene will be underexposed, move to a higher ISO.

3. My 10D and 20D bodies have a Custom Function (C Fnc 4) that allows the AF to be moved to the "*" (AE LOck) button. This allows focus to be locked independent of the shutter button. If your body does not support this function, you may need to use the AE Lock to set the exposure before recomposing the shot and shooting. If you have this function (C Func 4) available, it will help solve your question 1 also.

Posted: Sun Apr 22, 2007 2:46 pm

carpetpaul wrote:

1, my first question regarding zoom for accurate focus. I was once told that you could get a more accurate focus by zooming in on your subject when you focus, and then reducing the zoom for the shot.

You'd need a perfectly parfocal lens for that to work. I think most zooms are supposed to be parfocal but I doubt its perfect - there's got to be some error. You're probably better off just focusing at your actual shooting focal length.

Quote:

2, Whilst I understand the basics of photography, and have a simple understanding of the camera's instructions, I couldn't find a setting that would have the camera set the fastest possible shutter speed for each situation. I wanted (whilst shooting wildlife with a long lens) to be able to just shoot away knowing that the camera was doing it's best to avoid shake. It was suggsted to me to set Av to its widest setting, getting the most light into the camera and therefore forcing the fastest shutter speed, is this correct ?

The best you could probably do is shoot in Tv mode with a known-good shutter speed. If you see a blinking aperture you'll know you need to quickly adjust shutter speed (if you want to chance a blurry picture) or just give up the shot. In relatively stable light you could just fix your aperture & shutter in full manual mode and shoot like that.

Quote:

as, if I hold the shutter button half way to keep the focus, the exposure is going to stay locked too ?

Exposure isn't going to be that wildly sensitive as long as your first (eye-focused) exposure is accurate. I think the best metering mode for most situations is either center-weighted averaging or evaluative (the latter may be a bit unpredictable though in that you're camera is making decisions for you based on what it thinks the scene is - for example backlighting, etc). Don't mess with spot or partial until you're more comfortable and really need it. In the scheme of things I'm pretty technically competant (I'm not trying to be braggardly or anything, but it's true - artistically is a different matter ;) ) and I rarely use spot or partial - it's just too tricky. One thing you can do to give yourself about +/- 1.5 stops lattitude is shoot in raw mode and convert to jpeg later - this lets you adjust for exposure mistakes a bit more than large jpeg alone. Of course it's best to learn to get it correct in camera in the first place, so work on that.

Quote:

If you can offer me any more advice for shooting wilklife with the 450D I'd be very keen to learn

I think the best things to do are make sure you're using an exposure metering mode that gives you decent predictable results, keep your shutter speed at 1/(focal length * 1.6) minimum (unless you're panning and going for motion blur), use a tripod if possible, and most importantly focus on your composition and lighting more than the technical aspects. In most good lighting you'll almost always be able to shoot in aperture priority mode and get good results - you'll learn to switch to other shooting modes when the lighting demands it, for example you're right at the cusp of unholdable shutter speeds and you want to enfoce the 1/(focal length * 1.6) rule.

Remember you can practice all the technicalities to your heart's content on house plants or moving cars or whatever so you'll be prepared and quick on your feet when you're out chasing wild animals.

Joined: 27 Oct 2006 Posts: 20 Location: Blackpool UK

thankyou to both of you for the advice, I'm cetainly enjoying my camera and I'll continue to practice.

... I was sure (from the limited photography class I did years ago) that you could go right in on full zoom, then focus and then zoom right out, and that would give you a very accurate focus

.... but again, it does draw up the issue of setting the expose

I had the odd photo where the focus was out, or it wasn't exact, and I wondered if that technique could have helped, but in reality, it was likely movement of me, or that of the animal in the time of waiting for the shot between the focusing and the capture of the shot that sent the focus out when using the longer lenses.

thanks again

Paul.

Posted: Sat May 12, 2007 12:16 am

You either own a 350D or 400D but I don't think even in European or Asian markets is there a 450D but I might be wrong. Anyway on to your questions.

1 - Changing a focal length after foucsing can change the focus point. I would not do so, in fact your camera or lens manual both recommend against what you were told.

2 - Yes that will default to the fastest shutter speed with ambient lighting. It may not result in the sharpest image though, almost all lens are softer or sharper ar different apertures. My 100-400mm is best between f/7.1 - f/10, the Sigma 300-800mm f/5.6 is best at f/8 so that is what try to use in both cases. My cameras are always at iso 400 for a basic setting and I almost always shoot my wildlife in AV mode. If the light is low I work to be steadier and not to go wider.

3 - I change the focus point to the best one in able to frame the shot, but your camera has both a focus and/or exposure lock please refer to the manual for details but if you keep the shutter half depressed the focus and exposure will be locked while you recompose.

I tell a lot of people the hard part about shooting wildlife isn't the camera, it is the finding and getting close to the subjects that is hard. Get that down and practice with the camera until you know it functions and can change settings to meet conditions without thinking about it is imperative. Fumbling for a setting just won't work because the subject doesn't stay where you want it. To get good wildlife shots it takes time, a lot of it, did I say very very be patient?

Capture behavior, habitat and the "sense" of the animal, it makes an image better than just a portrait. See the shot below for an idea of what I mean. Get down or up to eye level, it makes the shot.

And finally for wildlife you will need the longest lens you can afford and will always want a longer one you don't think you could ever afford. With good skills in finding and getting close to subjects 400mm is the minmum I would suggest. Shorter than that will result in shots but to bring them up in an image will be big cropping and resulting in less detail and less than satisfactory results.

Joined: 27 Oct 2006 Posts: 20 Location: Blackpool UK

Thanks for the advice, I'm certainly clearing up some of the problems and issues that I've had, and I will contnue to practise.
I do find that my widest lens is not wide enough for landscapes...... and my longest lens (300mm) is not quite what I want to the wildlife, both will do until I have mastered the camera a little more !

many thanks

Paul Jones.