GXR情報

The A12 28mm F2.5 GR Lens as a Great Second Camera on Vacation (part 2)

2011-07-02
こんにちは。ふーです。

GR BLOGは海外の方にもご覧いただいているようですので、先日公開してご好評いただいている「特別寄稿:旅のサブカメラにも最高の画質を GR LENS A12 28mm F2.5」を特別に英語化して掲載しています。今回は後半の英語版です。
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In the last week's installment, I introduced the GR LENS A12 28mm unit's excellent image quality, which makes it a perfect second camera to my main DSLR. On vacation, however, the GXR is a better choice depending on the scene. One such case is hand-held shots under low light conditions.

6. Synergy between High ISO Performance and Silent Shutter
Both A12 28mm and 50m units are suitable for shooting nightscapes under ambient light, even without a tripod. Through my experience (since they are not described in the spec. sheet), there are basically two keys to realizing this feature:

- The sensor's high ISO performance (ISO800 usable for most pixel peepers) and the clever ISO control in the Auto-Hi mode. (Whereas you can only set the sensitivity in a full step increment in the manual ISO setting, the Auto-Hi mode tries to keep the sensitivity as low as possible using variable figures smaller than 1/3 of a step.)

- Minimal shutter lag and vibration of the leaf shutter which enables blur-free results at 1/10 second with ease, even without an anti-blur mechanism of any sort. (My personal limitation is around 1/6 sec. where the hit-rate is still above 50%.)

Hand-held slow shutter example, 28mm.
#309 ISO400, F2.5, 1/6 sec.
RES05309.JPG

R0013309.crop.jpg

I often choose the AUTO-High setting with the limitation at 800. This algorithm is very clever to strike the balance between the shutter speed and image quality (again, the noise/detail balance) of actual photos as in the following example (ISO497, 1/32 seconds).

autohigh.E.jpg

#516, ISO497, F2.5, 1/32 sec. -1.0EV
RES05516.JPG

Considering the noise at ISO800 to be acceptable level, I set the Noise Reduction to Off to avoid sacrificing any detail of the picture.

NRoff.E.jpg

The GXR A12 units are equipped with leaf shutter, unlike typical interchangeable lens cameras with focal plane shutters.

There are two advantages to the between-the-lens, leaf shutter:
1) Since the shutter diaphragm only travels one way in the direction of closing the iris (while the trigger is electronic), shutter lag is always minimal.

2) Since the diaphragms have much less inertia than the sets of blades seen in a focal plane shutter, the mechanical shock and noise caused by releasing the shutter is also minimal.

The combination of the APS-C sensor and this vibration-free, always-silent shutter makes GXR A12 units a more suitable gear for nightscape and ambient-light photography, but that's not all. The A12 units are also suitable for capturing subtle change in expressions of the subjects in portraits or wildlife photography, with its shutter lag (half-pressed and/or pre-focused) being shorter than that of a professional DSLR's.  

On the other hand, live view with focal plane shutter means the curtains are wide open to realize live view and the first curtain must be retracted right before exposure. This tends to cause a compromise between allowing noise or vibration for shorter lag and sacrificing shutter lag for less-noisy operation.

Of course, nothing is perfect and the leaf shutter has a demerit of not being able to run at the maximum speed at wide open, because the travel becomes longer as the aperture widens. This is why I couldn't show you a photo taken at wide open in broad daylight last week ("1 Edge-to-edge Sharpness"). <Link to last week's issue> However, this demerit can be somewhat offset by another merit that it synchronizes with flash at all speeds.

Other examples where lag and noise free leaf shutter works well

Jelly fish in the tank

#551 ISO800, F2.5, 1/6 sec.

RES05551.JPG

Noise at ISO800 (Noise Reduction: Off)

R0013551.noise.jpg

#555 ISO542, F2.5, 1/30 sec..

RES05555.JPG

Noise level of ISO542 (Noise Reduction: Off)

R0013555.noise.jpg

#559 ISO703, F2.5, 1/30 sec.

RES05559.JPG

Noise level of ISO703 (Noise Reduction: Off)

R0013559.noise.jpg

Fish in the tank

#573 ISO800 F2.5, 1/20 sec.
RES05573.JPG

Noise level of ISO800 (Noise Reduction: Off)

R0013573.noise.jpg

Features and Functions

1. Change Lenses Anytime, Anywhere
As the opportunity of switching lenses (28mm to 50mm or vise versa) increases, I enjoy the merit of interchangeable camera units, in which I don't have to hesitate to change lenses anytime. I am not talking about an extreme environment where a professional level weather sealing is required, but daily outdoor situations such as amid sandy wind or a sudden shower on the resort island. Actually, I chose which lens to use on my main DSLR before heading outdoors to avoid exposing bare mirror, sensor and the back of the lenses to the outdoor elements (the weather sealing only works when the lens is properly latched!), but didn't have the same fear about the GXR.

Windy beach

#772 ISO200, F8, 1/1000 sec.
RES05772.JPG

A beach where the sea sprays on my lens (Swimming is not allowed.)

#803 ISO200, F9, 1/1000 sec. -0.3EV
RES05803.JPG

#682, ISO200, F5, 1/200 sec., -0.3EV

Windy (more so than most people would imagine) Diamond Head summit
RES05682.JPG

2. Faster AF and Pinpoint AF Area
The new AF algorithm enables considerably faster auto focus by increasing the readout speed of the CMOS sensor. It is important to reiterate that the autofocus speed of A12 50mm also becomes on par with A12 28mm by a firmware update.

Actually, this is only half the story. Another critical improvement in the AF category is the introduction of pinpoint AF area. This is very useful when I move the AF target around the frame to obtain precise focus, and/or in the macro mode.

pinpoint.E.jpg

#444 ISO400, F3.5, 1/143 sec.
RES05444.JPG

Pinpoint focus on one eye only
Originally, I got frustrated with GXR's rather wide AF target area because the focus tended to gravitate towards a high-contrast object in proximity to the real subject, in this case, strands of fur closer to the lens than the eye. The Pinpoint AF area, as the name suggests, can avoid this problem.

R0013444.pinpoint.jpg

Faster and more accurate. The same story applies to the A12 50mm unit with the new firmware.

#724 <GR LENS A12 50mm> ISO400, F2.5, 1/40 sec., -0.3EV
RES05724.JPG

R0013724.pinpoint.jpg

3. Changing the Color Balance
Occasionally, the results of Multi-AUTO white balance may appear to be a bit too cool. This can be easily fixed on the spot, or later with the playback view.

(1) Changing the WB setting
#844 ISO800, F2.5, 1/13 sec. -0.3EV
RES05844.JPG

In this scene, Incandescent 2 worked better.

Incandescent2.e.jpg

#845 ISO800, F2.5, 1/13 sec. -0.3EV WB=Incandescent2
RES05845.JPG

(2) Post-processing the WB
#575 ISO200, F2.5, 1/40 sec.
RES05575.JPG

Sometimes you might not like the result of the Auto WB but it could be too difficult to determine the WB on the spot, or simply oversee it. In such cases, the "White Balance Compensation" function allows you to tamper with the color in two axes, Green-Magenta or Blue-Amber.

WB.E.jpg

RES06223.JPG

Wrap-up
In this week's installment, I introduced two cases where the GXR system shines even when I also carry around a DSLR with me. One is hand-held shots under low light conditions, and the other is that I don't have to expose the internal mechanism when changing lenses. This seems to me like having two fixed lens cameras with the bulk of a mirrorless camera body and two lenses.


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