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.