Branches

This scene caught my eye a few mornings ago. The bare branches in bright sunlight really stood out against the pattern and dark roof in shadow. I grabbed my G1X to record the scene before the light changed. A simple snapshot, right?

Unfortunately, from my only vantage point, the G1X did not quite have the zoom for the composition that I wanted. OK, I’ll just crop it. But what if I couldn’t crop or didn’t want to deal with editing? I then remembered the digital tele-converter feature of the G1X.

Changing to 1.5X digital tele-converter was all that was needed to get this composition. Of course, the image file is JPEG only. If I’d wanted to make a large print I would have shot in RAW then edited and cropped to taste but this snapshot is just what I wanted.

G1X: Digital Zoom and Resolution

Slide Show 1: G1X digital zoom examples

I made a mistake in an earlier post about the digital tele-converter feature of the G1X. My rationalization is that I’ve rarely used any sort of in-camera digital zoom because it is really just cropping; in other words, I’m not experienced with digital zoom.  If a picture is to be cropped then my preference is to crop in Photoshop. My mistake was in thinking that the standard digital zoom was not up-rezzed whereas the digital tele-converter zoom (the fixed 1.5 or 1.9 zoom) in the G1X was up-rezzed. I was wrong. Both standard and tele-converter digital zooms are up-rezzed to the full 4352x3264 resolution of the G1X.

My error has unnerved me and I now wonder if there is a possibility that other posts may also contain errors!

The slide show above illustrates the G1X digital zoom at several settings but here’s some background information. The G1X lens has an optical focal length of 15.1mm to 60.4mm – a 4X zoom. For small sensor cameras, optical focal length is often stated in terms of equivalent full frame 35mm film camera focal length. For the G1X, the equivalent focal length is 28mm to 112mm. Instead of writing out “equivalent” every time, I prefer to use “mme”. With digital zoom (cropping) the effective equivalent focal length of the G1X is 28mme to 448mme – a 16X zoom.

Digital zoom choices are made in the Main Menu. The menu item reads “Digital Zoom” and does not indicate “digital tele-converter”. Options are: OFF, 1.5X, 1.9X and Standard. The 1.5X and 1.9X options are “digital tele-converter”. In terms of image size, all options produce 4352x3264 pixels in 4:3 aspect ratio frames. Digital zoom is not available for other aspect ratio frames and not available in RAW mode.

Using Standard digital zoom, digital cropping begins once the optical zoom has reached its maximum. That is, digital cropping begins above the 112mme focal length. This also means that the largest aperture is f5.8 for standard digital zoom on the G1X.

 

Slide Show 2: G1X digital tele-converter examples

In contrast to Standard digital zoom, the digital tele-converter zoom factor (1.5 or 1.9) applies to all optical focal lengths. This means that the optical 28mme becomes 42mme and the optical 112mme becomes 168mme when the 1.5X digital tele-converter is activated. Additional digital zooming is not possible when in the digital tele-converter mode of digital zoom.

The advantage to the digital tele-converter is that larger apertures are available in comparison to the optical or Standard digital zoom. Suppose, for example, a given scene is best photographed at 85mme. The largest aperture for 85mme optical focal length is f5.6. Standard digital zoom applies only to focal lengths larger than 112mme. Using the 1.9X digital tele-converter feature, the same composition is available at an optical focal length of ~45mme for which the maximum aperture is f4. Therefore this scene could be captured at f5.6 with pure optical zoom or at f4 by using the 1.9X digital tele-converter.  Using the larger aperture means that a faster shutter speed or lower ISO can be used when in digital tele-converter mode.

To my surprise, the combination of digital tele-converter and larger apertures did not increase the amount of background blur, see Slide Show 2 above and notice the blur in the far background.  The explanation is that depth of field is increased at shorter focal lengths and this increase more than offsets the slight change in aperture even when the image is cropped.

Although my preference is to crop in Photoshop, the digital zoom and digital tele-converter features do have their place. 

G1X: A Short Walk

As the weather was very nice today, I found it convenient to take a short walk outside and slipped the G1X into my pants pocket^* to grab a few shots along the way.  Nothing particularly great about these shots; the G1X was in Av mode, JPEG only, ISO 100 or 400.  Exposure compensation was used to tweak the Av exposure – sometimes based on the histogram but more often as an adjustment for a second shot.  Exposure compensation for the above shot was +1/3.

As a measure of my humility, the above flower shot just didn’t work as I thought it might.  No exposure compensation.  My idea was to focus on the foreground and have the middle and background fade to extreme blur.  The largest aperture for that focal length was f5 and it simply was not enough.  Probably needed more like f2.

Staying with 16:9 aspect ratio, the above shot (which I call “Tree and Clouds”) was at full telephoto and f5.8.  No exposure compensation.

Back to a 4:3 aspect ratio above.  No exposure compensation.

I get tired of people taking pictures of ducks.  These are geese.  Taken using the 1.9x digital zoom feature.  No exposure compensation.

Staying with the 1.9x digital zoom but –2/3 exposure compensation.

A nice walk with a little photo practice along the way.

 

^* Said pocket being styled and designed for men of a certain age.

G1X: Flower Macros

                                      Fig. 1.  Full telephoto, 250D, 1.5x

Following my post about the G1X “macros” with and without the 250D close-up lens, a question came up about the relative effects of the 1.5x digital zoom feature.  Never having used those features, I didn’t know the answer so I did a little experimenting with/without 250D close-up lens and with/without digital zoom.

First off, everyone should realize that the 1.5 digital zoom works only in pure JPEG mode and only in 4:3 aspect ratio. It does not work in RAW or RAW+JPEG. It seems to me that the 1.5x digital zoom (said to be different from continuous digital zoom) crops the normal view and then uprezes that crop to the normal 4352x3264 pixels resolution of the G1X. Although I've not used this feature in the past, it actually seems to work well.  There is also a 1.9x digital zoom.  Figure 1 shows the image obtained with the G1X at full telephoto (60.4mm focal length), 1.5x digital zoom and the 250D attached.

                         Fig. 2.  Wide angle, without 250D, no digital zoom

At the opposite extreme of Figure 1, Figure 2 shows the image at minimum “macro” focus distance at wide angle (15.1mm focal length) and without the 250D and without any digital zoom.

To get the above and following pictures, I put the G1X on a tripod and attached the RS60-E3 wired remote trigger.  The G1X was set to JPEG mode, ISO 400, f11 and 1/30 second for all shots.  The subject (a beautiful yellow rose from our garden) was moved (trial and error) to the minimum focus distance for whatever configuration was being tested.  Lighting was done with a cheap LED continuous source, hand held and moved very close (typically about 9 inches) to the flower until the exposure compensation indicator read zero (got to post about that LED light some day).  The LED light was fitted with a CTO-like diffuser and, to my chagrin, the resulting white balance was not really tungsten – which is what I set on the G1X.  Consequently all photos taken were tweaked (by the same amount) in Photoshop.

To understand the results, one must realize that the minimum focus distance with the 250D is about 10 inches.  Therefore, the 250D plus telephoto is a powerful combination. If the goal is to produce the highest magnification uncropped JPEG image straight out of the G1X then the setup should be full telephoto with the 250D. This conclusion is not really different from that posted previously. 

In order of increasing magnification at the closest possible macro auto focus distance (by trial and error) here's what I saw:

1. max telephoto without 250D produced the smallest image, see Figure 3

2. wide angle image was slightly larger than max telephoto image, compare Figures 2 and 3

3. max telephoto without 250D using 1.5 digital zoom

4. wide angle image with 1.5 digital zoom.

5. wide angle image with 250D is essentially the same as #4, see Figure 4.

6. telephoto image with 250D is significantly larger than #5.  Compare Figures 1 and 5.

                     Fig. 3.  Maximum telephoto, without 250D, without digital zoom

                         Fig. 4.  Wide angle with 250D, without digital zoom

                       Fig. 5.  Telephoto with 250D, without digital zoom

Initially, there was some concern that the 1.9x digital zoom was an extreme and probably produced poor images.  However, the 1.9x image seemed OK to me.  Of course, the 1.5x and 1.9x digital zoom can be used with the 250D and the results looks OK to me.  In addition to viewing on-screen, I printed an 8x10 of each test and the results all looked OK to me. 

So, once again, I’ve learned something.  If I need a large print of a macro from the G1X, I’ll still use RAW with post processing and cropping.  But the 1.5x and 1.9x digital zoom provide usable options.