Panasonic Lumix DMC-G2 back-button auto focus

Back-button auto focus is a very useful technique in certain situations and is explained in plain English here (read from the beginning to the part about waiting for your subject to do something interesting). Basically back-button AF takes control of auto focus away from the shutter button and gives it to a button on the back of the camera.

The method described here has been tested on a Panasonic Lumix DMC-G2 and I’m almost certain that it will also work on the G1, GF1, GH1, and GH2. If you try this method on one of these cameras please post a comment and share the results.

Step 1: settings

  • AFS or AFC
  • one-area-focusing
  • AF/AE Lock set to AF*
  • AF/AE Lock Hold set to On*

Items marked * are in the Custom section of the menu.

Changing these settings in the middle of a shoot slows things down so I store them in one of the custom memories.

Step 2: shooting

One you’ve made the above changes or entered your custom mode put your AF frame over Subject A and press the AF/AE Lock button. ‘AFL’ will appear in the viewfinder and focus is now locked on Subject A until you press the AF/AE Lock button again. A half press on the shutter button will lock the exposure setting while you hold the button down (even though ‘AEL’ does not appear in the viewfinder), so the back button controls AF and the front button controls exposure.

To change the focus to Subject B place the AF frame over him and press the AF/AE Lock button twice.

When you see ‘AFL’ in the viewfinder you’re in back-button AF mode, and when you see ‘AFS’ or ‘AFC’ the shutter button is controlling both focus and exposure.

Doing it is a lot easier than reading about it.

This undocumented feature is part of the reason why, apart from the GF2, the Panasonic G series has been quite successful at serving both point-and-shoot people and advanced photographers. Some firmware changes would make the G2 even better for the latter group.

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Using a polarizing filter to reduce reflections and improve your photos

Ruth Renner took a photo of her cow’s eye and couldn’t get the detail that she wanted because the eye was acting like a mirror and reflecting an image of the surrounding paddock. Also, the black cow looked partly white due to light reflecting off her hairs. A polarizing filter is the widget that will reduce these reflections: if you’ve ever had polarized sunglasses you’ll have a good idea of what a polarizing filter does.

Polarizing filters not only reduce obvious reflections, they also reduce the reflections that you’re not aware of. Things like foliage reflect light and desaturate (water down) the colours, so a polarizer will give a pleasing result that shows the “real” colours of the foliage. They work best in bright, high-contrast light (i.e. when the shadows are really dark), and are generally best avoided in low contrast situations such as a heavily overcast day.

When your polarizing filter is on your camera you rotate it until you get the desired effect: generally the full effect will look awful, and somewhere around half way between minimum and maximim effect is about right. It’s all a matter of taste and experimentation. Polarizing filters are good for the following situations (this is not an exhaustive list):

  • taking photos at the beach, by a lake, or in the snow
  • taking photos of water: you can stop the water looking like a sheet of white and see some details under the water
  • taking close up photos of cows, as we all do
  • taking photos of foliage
  • taking photos of people wearing shiny nylon jackets: with a polarizer you can see the true colour and greatly reduce distracting reflections
  • photographing blue skies, with or without clouds. Clouds look superb when a polarizing filter is used
  • taking photos of things inside glass cases (without flash)
  • taking photos of people who are outdoors
  • generally if the sun is visible or it’s a bright overcast day your photos will benefit from some degree of polarization. Just experiment with different lighting conditions and different rotations of the filter, but avoid the temptation to leave the filter on all the time.

How do you attach a polarizing filter to your camera?

If you’ve got a SLR just buy one of the right size and screw it on to the end of your lens.

Canon Conversion Lens Adaptor LA-DC58K for Canon G10I know that Ruth’s camera is a Canon compact zoom that will take an adapter tube (pictured). This is literally a tube: you attach one end to the camera and the polarizing filter screws into the other end. In this case it’s a good idea to get a lens cap (with lanyard/retaining cord) to protect the filter. The adapter tube will also protect the delicate zoom mechanism. The Canon adapter tube is made of flimsy plastic, but metal aftermarket versions are available.

Only a minority of cameras are made to take adapter tubes, so what do you do if yours isn’t one of them? You can just hold the filter in front of the lens, but in my experience this is very awkward, you’re likely to have blurred photos as a result of camera shake, and you’re likely to drop an expensive filter. The Cokin Filterfast might be the way to go for you: one advantage of this system is it will fit a wide range of cameras, so you can keep it when you get a new camera or share it with family members.

One thing I have done when I don’t have a polarizing filter with me is hold my high quality polarized sunglasses in front of the camera lens. I don’t recommend this because it’s awkward, camera shake is likely, sunglasses usually aren’t very clean, and it’s not as effective as using a proper polarizing filter. However, if done with care it does improve the photo and that’s what matters.

Conclusion

A polarizing filter is a simple device, and with a bit of practise you can use one to greatly improve your photos. I highly recommend getting one.

Click here to view some of my photos taken at the beach on a cloudless day using a polarizing filter. Without a polarizing filter the colours would have looked desaturated (washed out) due to all the reflections from sand, water and so. With the polarizing filter the colours are saturated and natural; the effect is most noticeable when you look at the sea, which has a nice colour instead of looking pale or like a sheet of white. Photos 1 and 2 show how a polarizing filter allows you to see what’s under the surface of the rock pool, while in photos 3-5 the rock pools look more like they would without a polarizing filter.

Experiment and enjoy – with a digital camera your only cost is time.

For cheap-but-decent polarizing filters I recommend John Thomson Photography. He also supplies lens adapter tubes.

Click here to go to my website and see more photos

Having trouble with rechargeable batteries? 

Some cameras take AA or AAA rechargeable batteries and I personally prefer this because you’re not locked into buying a proprietary battery and in an emergency you can buy batteries just about anywhere. They are heavier and the flash recycle time is longer when compared to lithium batteries.

The best current technology for rechargeable AA and AAA batteries is nickel metal hydride (NiMH). The trouble with these is that they have a high self-discharge rate, i.e. they rapidly lose charge just sitting on your shelf or in your camera. Then you go to use your camera and swear when the batteries go flat after five minutes.

The best NiMH batteries are a type called Eneloop, or one of the equivalents available with different names. The distinguishing feature is the fact that they’re charged and ready to use when you buy them. These have a very low self-discharge rate and Eneloop claims to retain 90% of the charge after six months (the conventional type would be dead long before then). I don’t know how good the other brands are, but I’ve been using Eneloop for a few years and they’ve been superb: they also seem to last longer in the camera when compared to conventional NiMH batteries.

All rechargeable batteries will die after a certain number of recharges, and the recharger that you use makes a big difference here. The type of charger that just charges for a fixed time period will overcharge your batteries and shorten their life significantly. The best type measures the charge in the battery, temperature, and other factors to give your battery just what it needs and no more.

I’ve been using an Energizer CH1HR for about 2 years and had no trouble with it. It’s a one-hour charger and gives a trickle charge to maintain the battery after it’s charged. If you find the appropriate cord you can also use this charger in a car. Click here to view a data sheet (PDF 54 KB).

A final note: I keep my NiMH batteries in the fridge between uses. Eneloop’s information says that the batteries last longer when stored at low temperatures, but must be kept dry. Eneloop also says that the batteries can tolerate a storage temperature of -20degC and be used or charged at 0degC, so refrigeration is no problem.


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