Saturday, May 31, 2008

G9: Variations in Focusing Outdoor Scenes

The first posting in this series on focusing showed the five auto focus modes possible with the G9. The second posting explained how the hyperfocal and depth-of-field concepts benefit and limit focusing. Now let’s examine and compare the results when using the various auto focus modes. For this posting, a landscape scene was photographed using each auto focus mode. The G9 was mounted on a tripod and the composition was not changed from shot to shot. The focal length was near the middle of the zoom range. Exposure was set at 1/60 sec and f4.5 in manual exposure mode for ISO80 sensitivity for all shots. The G9 was set for Raw+jpg mode but all images here are from the in-camera jpg for consistency. The image shown here is the first one taken; the auto focus was set for Flexizone using the small frame because this is the way I normally focus. The small focus frame was placed on the front of the canoe.

The G9 has a nice feature for checking focus that I’d forgotten about. Here’s the display showing the focus point for the above image. This feature is available in both shooting (page 86) or playback modes (page 162). (But if your practice is to focus, recompose and shoot, as is mine, then the focus check does not remember that first focus point.) I paced off the distance from the G9 to the canoe; it was about 115 feet. My workhorse software, BreezeBrowser, says that the focus distance was set at 82 feet. Strangely, neither Canon’s ZoomBrowser nor Adobe’s Photoshop include focus distance in the image properties.

From the G9 Hyperfocal Chart, the hyperfocal distance for 25mm focal length and f4.5 is 76 feet. With the focus distance actually set at 82 feet, everything from 39 feet to infinity should be in focus. (OK, I didn’t think ahead on this one but used DofMaster directly.) Although the basis of depth-of-field is not pixel peeking, when examining the full image file, it seems to me that the in-focus distances are from about halfway to the canoe to infinity – as predicted in the DofMaster calculation. So even though the G9 selected the focus point I wanted, it set a slightly different actual distance; however, the final result was essentially the same as if the G9 had set the exact distance.

What about the other focus modes? Results varied.

The large Flexizone frame also fixed on the front of the canoe but the focus distance was actually set at 66 feet. This is probably because the large focus frame includes more of the foreground than does the small frame. Results were good with, by computation, everything from 35 feet to 493 feet in focus.

Surprisingly, the small AiAF frames did not do very well and I don’t understand why. The focus distance was set for only 43 feet so everything from 28 to 99 feet was in focus but the distant background was blurred. The large AiAF frame actually was more accurate than the small frame with respect to the distance to the canoe. Using large frame AiAF, the focus distance was set at 72 feet.

Using face detection focusing but without faces in the scene, the G9 logic switches to large frame AiAF and, again, the focus distance was set at 72 feet.

Lastly, I switched to manual focus and dialed in infinity. BreezeBrowser interpreted this setting as 216 feet. In that case, everything from 56 feet to infinity should be in focus. Pixel peeking the manually focused image, I see the relative differences but differences are small except in comparison to the small AiAF closer focused image.

Based on this experience, I’ll be continuing my current practice: small frame Flexizone, focus, recompose, shoot. But indoor photography, usually without the benefits of hyperfocal focusing, can be more challenging. Next I’ll take a closer look at face detection.

Thursday, May 29, 2008

Strobist Lighting DVD

The Strobist, David Hobby, has released a set of eight DVDs illustrating his equipment and techniques for off-camera flash photography. David primarily uses Nikon DSLR cameras and flashes but also uses a Canon G9 with those same flash units. If you are at all interested in learning off-camera flash techniques, you should check out the Strobist blog.

My own set of DVDs is on order.

Sunday, May 25, 2008

G9 Hyperfocal Chart

Continuing the series on focusing the G9, knowledge of the hyperfocal distance is extremely useful when focusing any camera. Previous postings have included observations about the G9’s use of hyperfocal focusing and depth of field for closeups.

Somewhat loosely speaking, but easy to remember, is that if a camera is set for the hyperfocal distance then everything from that distance to infinity is acceptably in focus. In fact, everything from half that distance to infinity is in focus. For more details, check Wikipedia .

A most useful reference for both hyperfocal distance and depth of field is DOFMaster . Since both hyperfocal distance and depth of field vary with digital sensor size and focal length, here’s a chart of hyperfocal focusing distance specifically for the Canon G9 that was made by using the DOFMaster online calculations.

In addition to the hyperfocal distance, the table includes the near/far distance that is in focus when the G9 is focused at 10 feet. Why 10 feet? When the G9 is first turned on and switched to manual focus, it is set for (roughly) 10 feet.

Here’s an example of how the chart can be used. With your G9 turned off, set the Av mode at f5.6. Now turn the G9 on. The default focal length is the wide angle (7.4mm focal length) when the G9 comes on in Av mode. Immediately, switch to manual focus. You’ll see that the default focus distance is about 10 feet. Referring to the chart above for the 7.4mm lens, the hyperfocal length at an aperture of f5.6 is 5.3 feet. This means that, if the focus distance had been set for 5.3 feet then every distance from 2.65 feet (=5.3/2) to infinity would have been in focus. However, the default distance is 10 feet so everything from 3.5 feet (near focus) to infinity is in focus.

The G9 almost does not require focusing at the wide angle setting! But this happy situation changes dramatically at the longer focal lengths as shown in the chart.

Since aperture, focal length and manual focus distance can be saved as a custom setting (page 109 in the manual), the G9 can be preset for special situations -- including hyperfocal focusing.

Friday, May 23, 2008

G9: Focus on Focusing

The G9 is an extremely versatile camera. Among its many options are (at least) five different choices for automatic focusing methods plus manual focus. I’ve always used the same method in the past but it is past time to learn the others so the next several posting will be about focusing the G9.

The G9 automatic focus methods are:

Flexizone – a single rectangular frame normally in the center of the display but which can be moved as desired. The frame can be large or small. The G9 focusing logic sets the focus distance so that the object in this frame is in focus.

AiAF – A 3x3 matrix of rectangular frames in the center of the display. These frames can be large or small. Only the small frame matrix can be moved off center. The G9 focusing logic somehow selects one or more of these frames and sets the focus distance accordingly. (“AiAF” apparently means “Artificial Intelligence Auto Focus” but I can’t find that definition in the manual.)

Face Detection – Magically, the G9 detects faces (or objects resembling faces) and sets the focus accordingly.

The autofocus mode is a menu setting (page 116 of the manual) as shown above but can also be set with a few button presses on the back of the G9 as shown here. First, with the G9 in shooting mode, press the AF frame button (numbered 19 on page 42 of the manual) shown circled here. The display will change as shown (but with the current AF frame selection). The AF frame selection is then toggled between Flexizone, AiAF and Face Detection by pressing the Menu button, examples are shown below.

For Flexizone and AiAF, the size of the frame can be changed by pressing the Display button, the smaller frames are shown below. Both Flexizone and the small AiAF frames can be moved with the Control Dial.

When in Face Detection mode, pressing the Display button indicates how many faces are detected.

When using the G9, I always recommend pressing the shutter button halfway to achieve focus. Once focus is achieved, the G9 gives two quick beeps and the focus frame turns green.

My normal practice is to use the small Flexizone frame in the center position to obtain focus on the subject of interest. I press the shutter button halfway to achieve focus, hold the button at the halfway position, recompose and shoot. To get a second or similar shot, I might switch to manual focus because the manual focus position is retained until the next autofocus.

Wednesday, May 21, 2008

My G3 Gallery

Since I've owned and used a Canon G3 for many years, I have quite a few pictures taken with the G3. I’ve posted a G3 gallery alongside my existing G9 gallery on SmugMug.

For both galleries, the images have been resized to display full screen at 1024x768. The G9 gallery is more representation of where I am at the moment whereas the G3 shows my learning curve over the past several years. In assembling and posting these galleries, there was no conscious effort to compare cameras, styles or techniques – just some photos that I like.

I stand by my previous statement that, for purposes of full screen viewing, it would be difficult to choose one G series camera over another – for that matter, many cameras produce similar screen images. (But I’ll grant that pixel peeping, cropping and print making are a different subject!)

Wednesday, May 7, 2008

G9 with Cactus Wireless Flash Triggers

The Canon G9 has a hot shoe for external flash but the camera is so small and some flash units so large that the combination can look ridiculous. Even so, an external flash is quite a nice accessory for the G9. Naturally, recent Canon flashes work well with the G9 but other flash units can also be used.

External flash is not only more powerful but more versatile than small internal flash units. For example, the Canon 580EX shown here is pointed upward so that the light bounces off the ceiling to provide a softer lighting effect. Even more lighting effects and variations are made possible by removing the flash from the camera. But how can the flash be triggered if it is not on the camera?

Canon offers a number of flash accessories and connectors but these can be quite pricey for the hobbist. A relatively straightforward method of connecting an off-camera flash is to put one adapter on the hotshoe, another adapter on the flash and connect the two adapters with a wire/cable. Rather than deal with wires, many photographers prefer a wireless flash trigger. Triggers such as the Pocket Wizard are legendary for performance and reliability but, again, are expensive for the hobbyist.

Last year, shortly before getting my G9, I became aware of a cheap wireless flash trigger, the Cactus V2s – sometimes called the “eBay trigger”. After reading everything I could find – pro and con -- about this cheap flash trigger, I decided to try a set. Mine work fine more than 90% of the time and have been very useful in learning off-camera flash techniques. In fact, now I have several units and all of them work fine.

Cowardly Disclaimer: My Cactus wireless triggers work OK. Yours may not -- so don’t blame me if they don’t!

Some photographers swear by the Cactus triggers and some swear at them! Problems include: just won’t work, flimsy construction, batteries loose, battery connection loose, PC (wire) connection bad, incompatible with some flash units (said to be fixed with the V2s), short range, etc., etc. Lots of successes, lots of failures.

Some inventive users have taken up the challenge of modifying their Cactus wireless triggers but since mine worked OK, I’ve not modified them at all. Even if the photographic results were not improved, the handling of the G9 is much, much improved by mounting the small Cactus trigger instead of a huge flash.

At the same time, the Cactus receiver is even smaller than the G9 and mounting a flash unit on the receiver creates a very flimsy combination. My solution is to use lots of gaffer tape. I suspect (no data) that the Cactus units are more reliable when the flash is mounted directly on the receiver. That’s certainly been my experience. This Nikon SB-28 was triggered by the Cactus V2s system from my G9 about six feet away.

On a good day, my Cactus system works outdoors at a line-of-sight range of 150 feet. Indoors, it usually works well through hollow dry walls into the next room. It synchronizes with the G9 at shutter speeds up to 1/640 second and sometimes faster. I’ve used it with Canon 580EX and 420EX, Vivitar 285HV and 2600, Nikon SB-28, SB-24, and SB-23 – even a Holga 120.

Off-camera flash is a powerful tool and I’m trying to learn to use it. For off-camera flash techniques, I rely on “The Strobist”, David Hobby, and study his tutorials.

David has written about the Cactus units as well as other triggering methods. He even owna a G9 and has written about it as well. The Strobist blog is updated regularly so I check in almost every day – you should too!

Saturday, May 3, 2008

Lensmate and Canon Adapters for the G9

The Canon G9 has a non-interchangeable zoom lens without threads for attaching filters. What? I thought … Yes, there are accessory lens and filters for the G9. These accessories are attached to a simple tubular adapter that fits over the lens as shown here. The G7 and G9 use the same adapter, Canon LA-DC58H. To attach the adapter, first remove the decorative ring which covers and protects the connection at the camera. The adapter has standard 58mm filter threads so anything that has 58mm threads can be attached (even a reversed lens!). Popular accessories are filters, especially polarizing filters , and lenses. Canon makes wide angle, telephoto and macro accessory lenses.

In addition to Canon, there are third party manufacturers for adapters, lenses and other accessories. One of the most popular is Lensmate. A U.S. company, Lensmate makes adapters for many different Canon cameras and also sells compatible lenses and filters to match its adapters. The Lensmate web site is an excellent source of information including comparisons of many different attachment lenses and filters: wide angle, telephoto and macro.

Shown above are the Canon and Lensmate adapters for the Canon G7/G9. The adapters are very similar except that the Canon adapter is made of hard plastic and the Lensmate adapter is made of anodized aluminium.

The Lensmate adapter comes with a protective end cap and can be ordered with a cover as shown here. Both the Canon and Lensmate adapters work very well and protect the lens while making the G9 even more versatile. I first used the Canon but now keep the Lensmate version in my bag after a filter got stuck on the Canon version. (The filter probably became stuck because of thermal expansion. Later, it unscrewed easily with no damage to filter or adapter.)

There is a wealth of information on the Lensmate website, including Richard Franiec’s line of accessories. Well worth checking out!