LX7 - does its IQ compete with e.g. Sony RX100?

Started Apr 6, 2013 | Discussions thread
ultimitsu
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Re: LX7 - does its IQ compete with e.g. Sony RX100?
In reply to Sean Nelson, Apr 9, 2013

Sean Nelson wrote:

ultimitsu wrote:

"Faster" refers to the ability to use faster shutter speed while maintaining the same IQ.

I know what you mean by "faster shutter speed to maintain the same IQ", but I doubt many other people think that way.

They should, because that is what it ultimately comes down to.

For example, does "same IQ" mean a shutter speed fast enough to eliminate motion blur?   No, that's not what you mean.   You mean a shutter speed that lets enough light hit the sensor to end up with the same amount of noise.   That's really not the way most people think about shutter speed.

Then they are mistaken, wouldn't you say?

For the record, a lens of f/2.8 aperture and the same field of view shooting the same scene at the same ISO setting can be used with the same shutter speed on cameras with varying sized sensors.  That's because lenses set to the same f/ratio illuminate the sensor with the same brightness per unit of area (number of photons per square millimeter, for example).

We are agreement.

By "total amount of light" he doesn't mean the brightness of the image (that's solely governed by f/stop), he means the brightness times the sensor area.   A larger sensor requires more total light to illuminate because there's more area to cover - just like a 60" TV requires more total light to illuminate than a 30" TV, even if the brightness per square inch is the same.   You need more bulbs back there to illuminate the extra area of the larger picture.

Actually I think you have misunderstood me. I do mean the the image.

What determines the quality of the image is the amount of light received by the whole sensor (which turns into the whole image).

For example assume we have a small and large sensor getting the same FOV. If we have the same sized aperture (same sized hole), the F-number will be different, and for the large sensor, light is spread across a larger area, for the smaller sensor light is more concentrated. but the two images should be the same IQ.

But if we have two different sized holes which result in the same F-number, then the larger hole passes more light and the larger sensor collects more light. its IQ must be better than the small sensor getting less light from the smaller hole.

But once most people choose a camera, they stop worrying about comparisons with other cameras.   They decide how much noise they're willing to live with, choose a maximum ISO accordingly, and from that point on they only worry about f/ratio and shutter speed.

That is what people normally do. In this thread however the comparison is between LX7 and RX100. RX100 has a much larger sensor with a larger-but-not-proportionally-larger aperture hole. Net result is at the same FOV RX100 will get more light and it would result in higher IQ, or it can afford faster shutter speed and get the same IQ as LX7. Thus it is false to claim LX7 has a faster lens.

LX7 does have a brighter lens if we are only concerned with per area brightness. If we are concerned with per image brightness, LX7's lens is not brighter.

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