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The Canon PowerShot G1 X Mark II - with a real cropped sensor

Doug Kerr

Well-known member
I put this note in this section because the subject camera - like every non-film camera discussed in this forum - is a "digicam".

Canon has announced the new PowerShot G1 X Mark II camera.

The sensor and format sizes

You know that I hate the use of the term "crop" or "cropped" for a sensor that is smaller than a certain well-known film format.
My favorite crop camera is my Folding Kodak 3A, formerly the property of the US Department of Agriculture.​
But here, the term is apt. The G1 X II has a Canon-made CMOS sensor whose overall dimensions are apparently 18.7 mm × 14.0 mm, the same size as in the PowerShot G1 X. But it is not (quite) all used for any of the operating formats. Only a "crop" of the full sensor is used.

For the 3:2 formats (including 4352 px × 2904 px), the format size at the sensor is apparently 18.7 mm × 12.4 mm. For the 4:3 formats (including 4160 px × 3120 px), the format size at the sensor is apparently 17.9 mm × 13.3 mm. The pixel pitch is about 4.3 µm.

In the repulsive "Vidicon bottle diameter" convention, this sensor size is described as "1.5 inch". For those who prefer the "inverse Vidicon bottle diameter" convention (used to produce a larger number for small sensors), that would be "1/0.67 inch".

More directly, this is a 23.4 mm sensor.

Sensitivities of ISO 100-12,800 are offered (presumably SOS/REI).

The lens

The G1 X Mark II has a fixed lens, with a ff35 equivalent focal length range of 24-120mm, having a maximum aperture of f/2.0-f/3.9 over the focal length range.

Viewing organs

The G1 X Mark II of itself has only one viewing organ, a "3 inch" tiltable back panel LCD screen, 1.04 Mdots.

It has no optical viewfinder.

It can be equipped with the new Canon EVF-DC1 electronic viewfinder, said to be 2.36 Mpx. (I hope that is not actually 2.36 Mdots.) It can tilt upward. It goes in the accessory shoe, so of course with it on board one could not use an external flash unit.

I will of course be eager to learn of the behavior of this new EVF.

Get a grip

There will be a "grip" for the G1 X Mark II (sold only through the Canon online store). This is apparently intended to give "the feel of a DSLR camera".

Price

The US list price of the G1 X Mark II is announced at USD 799.00. I think no price has yet been announced for the EVF-DC1 or the grip.

Best regards,

Doug
 

Asher Kelman

OPF Owner/Editor-in-Chief
Doug,

So what's the focal length multiplying factor and how do we get an equivalent f stop of 3.5?

Thanks,

Asher
 

Doug Kerr

Well-known member
Hi, Asher,

So what's the focal length multiplying factor

I assume you are speaking of the full-frame 35-mm equivalent focal length factor.

In particular, if we consider the 3:2 format modes, that would be 1.79.

and how do we get an equivalent f stop of 3.5?

I don't know what you mean by that. Of course, the exposure impact of an f-number does not depend on format size.

My guess is that you are speaking of the effect of format size on the depth of field given by a particular f-number in combination with certain other factors affecting depth of field being "the same".

But we need to be explicit what we mean by "those other factors being the same".

For example:

1. Do we mean that the distance at which focus is set (and also the distance to the subject element we want in best focus) will be the same. Almost certainly. (I do the easiest one first!)

2. Do we mean that the focal length used would give the same field of view in both format size cameras? Probably. (That's the next easiest.)

3. Do we mean that the circle of confusion diameter limit (COCDL), our criterion of "how much blurring will be considered negligible", that we will choose will be:

a. The same a fraction of the format diagonal dimensions?

b. The same in terms of the resolution of the system (or more simplistically, the pixel pitch)?​

If b, then we must presume some pixel pitch for the full-frame 35-mm format size camera were are using for comparison.

Let me for the moment adopt the mentioned choice for 1 and 2 and, for 3, choice b.

Then, the f-number we would use on this camera to give the same depth of field as would be given by an aperture of f/3.5 on a full-frame 35-mm format size camera would be almost exactly f/2.0.

Of course if you mean something else, or if indeed you are speaking of depth of field, but you would wish to assume a different criterion for COCDL, then the result would be something else.

Best regards,

Doug
 

Asher Kelman

OPF Owner/Editor-in-Chief
Thanks Doug for conjugating all the possible options here!

So the sensor here seems a little bigger than the 4/3 class of sensors.

As to the 3.5, I was simply referring to you use of f 3.5 equivalent in your discussion!

Asher
 

Doug Kerr

Well-known member
Hi, Asher,

Thanks Doug for conjugating all the possible options here!

So the sensor here seems a little bigger than the 4/3 class of sensors.

Right.

As to the 3.5, I was simply referring to you use of f 3.5 equivalent in your discussion!
How curious. I can't find where I used that.

Are you by any chance referring to "ff35"? Sorry - that is my shorthand for "full-frame 35 mm". (As contrasted to, for example, half frame 8x10.)

I always call f/3.5 "f/3.5".

Best regards,

Doug
 

Asher Kelman

OPF Owner/Editor-in-Chief
Hi, Asher,



Right.


How curious. I can't find where I used that.

Are you by any chance referring to "ff35"? Sorry - that is my shorthand for "full-frame 35 mm". (As contrasted to, for example, half frame 8x10.)

I always call f/3.5 "f/3.5".

Best regards,

Doug

Still, by coincidence, we understand now that the "appearance" of the image, (at the same camera to subject distance, at f 2.0 on the new canon digicam would be similar as with an equivalent, FF35, full frame focal length at f3.5.

Asher
 
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