We all have bad habits. Here is a list of habits that photographers need to break.
1. Holding the camera with the left hand over the lens
Your left hand thumb should be facing forward, not down. With your left hand under the lens, you have much more control and stability. It means you can relax your right hand and not introduce any shake from holding the camera too tight. When I see tourists, especially ones with big, expensive cameras with their left hands over the top of the lens I have a mixed emotion of wanting to slap them and wanting to help them. But usually I just look away.
2. Lens hood backwards
The lens hood is the best thing for your camera and your photos. It cuts down on stray light that causes glare on the front of your lens. It protects the front element from rain, and from damage when you drop your lens. If you've just taken your camera out of the bag to get a snapshot of something in a hurry, okay, I accept you can have the hood the wrong way around. But by the time you line up your third shot, just do us all a favour and take a moment to put the hood on properly.
Chimping is the action of photographers checking the screen on the camera, sometimes accompanied by ooo, ooo, aaah sounds. Checking the exposure and general framing from time-to-time is okay, but not after every shot. Concentrate on getting the next shot and save reviewing your images for when you get home. That said, the immediate feedback from the screen is a great learning tool. Certainly use it to improve the next shot you take, but break the habit of chimping just because you can.
4. Shooting in bad light
Middle of the day in bright sunshine. In a dark room. In a stadium. Lights directly from above (see Direction post). Mix of daylight and room lights (see Rainbow post). If you can't get the light to flatter your subject, perhaps just just enjoy the moment and leave your camera in the bag.
5. Subject in the centre
You know about the Rule of Thirds, and that it is more of a guideline than a rule. It is your artistic prerogative to place the subject anywhere you like in the frame, but I challenge you to break the habit of centralising your subject. (See Rules post) Try framing differently to give a different feel to your images.
6. Taking one shot
One-and-done is okay, but what other angles or orientations or lighting opportunities are you missing out on? You don't have to "work the scene" and take hundreds from every conceivable angle but at least try a few "creative extras". Maybe the first shot is the one you land up using, but what else can you learn from trying different angles, exposure, depth of field, changing the focus point, lighting, etc...
7. Pixel peeping
Pixel peeping is the habit of getting a photo onto the computer to zoom in to the fine detail, and then often critisizing the lens or the camera or the technique or the photographer, or moaning about the shape of the bokeh or the chromatic aberration or the grain or the focus or shape of the catch lights or whatever. Like chimping, pixel peeping is a great tool to learn about the detail of an image. Use it to learn and improve your next shot. But like chimping, break the habit of pixel peeping just because you can.
8. Bad background
Trees or lampposts stick out of your subject's head is not a flattering look. Most of the time. Actually this doesn't only apply to backgrounds - any element of the image that distracts from the subject should be excluded. Move yourself, or your camera, or your subject to make sure that the people that view this image in the future know immediately what they are supposed to be looking at. Don't forget depth of field may be a useful technique here too.
9. Staying in Auto
You've spent a fair bit on money on a nice camera that has some great technology that produces some nice photos. But it is just a machine, and you're the artist. Take it out of Auto, and use those other modes to dial in your artistic intent. Over the course of these past few months, I've mentioned using Aperture Priority (Av) mode to control depth of field, using spot metering to get the Exposure you want, and using the centre focus point with the Focus and Recompose technique to get your subject in focus. Auto might be okay for snapshots, but it doesn't produce great shots.
We've all got GAS. That's Gear Acquisition Syndrome in case you're wondering. It's good to build up your knowledge about gear: What's the latest camera? What are the characteristics of that lens or tripod? What's the the guide number of that flash? Which camera has the best high ISO performance? But before any purchase, justify honestly whether it is a "want" or a "need" - will the gadget provide your photography with any tangible benefit, or is it just the lust of some some short term shopping therapy? That said, some stuff is cheap and just fun to play with and learn from, and that's a good thing. Get your gadgets on Amazon, and don't forget to click on the link on this page. (Clicking the Amazon link costs you nothing extra but I might get a few pennies back from Amazon. It's your way of helping me to keep this website alive.)
Speaking of GAS, recently I was just about to trade in one of my lenses because I wasn't happy with the images it was producing (because I was pixel peeping!). But the price of a replacement was out of my budget, so, with some experimenting I have changed my technique when using this lens and happier than ever with the results. Win-win at no extra cost!
Like most things in life, moderation is a good course to follow. Having habits that don't contribute positively to our lives and photography will only distract. Break the habit!