ISO 100 on M10

[digitalfx]

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My head hurts. #Ijustwannaknowifishoulduseiso100

 

 

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[adan]

Yes.

[otto.f]

My head hurts. #Ijustwannaknowifishoulduseiso100

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It would be very unLeica-ish to put the 100ISO on the hardware button if it would have been a compromise in IQ. Just as there is the possibility for 1/3 increments in ISO via the Menu, they would have put the 100 as PULL in the Menu, like in the M9 and M9M

[edwardkaraa]

I think it's a very common occurence since film days, when Tri-X was actually ISO 320 and velvia ISO 40, instead of the ISO 400 and 50 written on the box. If the base ISO of the M10 is actually around 135, the most logical thing is to rate it at either 125 or 160, but probably Leica decided to rate it at 200 because users prefer round figures, and adjust the camera meter accordingly to give correct exposure at iso 135. All digital camera manufacturers do it all the time.

 

Which actually means:

 

1. When you shoot at ISO 200, you are actualy shooting at ISO 135 (or whatever the real base ISO is).

2. Every ISO step of the M10 is overrated by 1/2 of a stop. (Nice for marketing purposes).

3. ISO 100 is a pull, but only by around 1/2 stop, hence the insignificant IQ loss.

 

And evidently, if you check DXOmark measurements of the M240, you will find that ISO 100 and 200 are identically rated at ISO 134. https://www.dxomark.com/Cameras/Leica/M-Typ-240---Measurements.

 

All ISO values from ISO 200 upwards are actually overrated by 1/2 stop as you can see in the graph.

 

This should prove my point.

[adan]

Yes - and ISO 200 is a push of about the same amount. Thus the DR ends up being slightly and about equally degraded from the maximum, which would be at a camera setting for ISO 135 - if such existed. And which my M10 field testing (as opposed to lab testing) seems to reflect - DR covers about the same net range at either 100 or 200.

 

In theory we could achieve that by going to totally manual exposure, and adjusting the aperture or shutter speed 1/2 stop under at 100 or 1/2 stop overexposure at 200, from what the M10 meter recommends. Not with exposure compensation though, since that is stepped in thirds of a stop, thus putting us closer, but still bracketing the ideal of 135 with 125, or 160.

 

(But that is obsessing down to the level of 1/6th stop - at which point my brain starts to hurt along with digitalfx's   - and likely very hard to actually see, outside of a lab.)

 

And all that assumes the M10 exactly follows the DxO results for the M240 - we'll have to see if DxO actually confirms all this when they chart the M10 itself.

____________

 

An operational difference between film and digital is that there is/was no way for Kodak or Ilford to affect your Leica or Nikon or Sekonic meter. Unless, in the DX-coding era, they jimmied the DX coding. Which people would notice - "How come in DX-ISO, my meter sets to 320 for Tri-X?!"

 

Now, with everything in the hands of the camera-makers (the actual silicon sensitivity, the metering, some initial processing) - it can all be massaged in the Maestro II. What's the ISO speed? - what the Maestro tells you it is. What's the actual correct exposure? - what the Maestro II tells you it is. What's the actual pull or push applied? - the Maestro II doesn't reveal that secret.

 

Not a conspiracy theory, because the camera does have to produce good, judgable results in the end. But exactly what goes on in the black box, we don't always know.

[edwardkaraa]

Hi Adan. I agree with everything you wrote above except for the 200 being a push. In fact, even though the setting says 200, the actual value is lower. The camera meter knows that and exposes accordingly. An external meter doesn't know, so when the scene is metered at ISO 200 the shot is underexposed. But anyway I can see from the second part of your post that you expressed a similar view.

[adan]

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Hi, Edward - so if, as you theorize, the M10 when set to ISO 200 actually exposes for an effective ISO 135, what effective ISO does it actually expose for when set to ISO 100?

 

In other words, if the light and aperture remain the same, and the M10 meter exposes a subject at 1/1000 sec. at ISO 200, what shutter speed will it pick at ISO 100?

 

How much additional exposure (or overexposure) will that be, if the base ISO is 135? I.E. how much "pull processing" will be needed, in f/stops, to compensate for the extra exposure?

 

(All this, of course, assumes the M10 follows the ISO pattern that DxO records for the M240. Which may or may not be correct.)

[Steve Ash]

 

 

 

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[01af]

Where is this 'ISO 135' nonsense coming from!?

[jaapv]

A discrepancy between the setting on the camera and an external exposure meter. Which is as old as exposure metering and quite normal in digital photography as the values are defined differently between film and digital in the ISO norm, leaving the camera makers quite a bit of leeway in the actual values.

[edwardkaraa]

Hi, Edward - so if, as you theorize, the M10 when set to ISO 200 actually exposes for an effective ISO 135, what effective ISO does it actually expose for when set to ISO 100?

 

In other words, if the light and aperture remain the same, and the M10 meter exposes a subject at 1/1000 sec. at ISO 200, what shutter speed will it pick at ISO 100?

 

How much additional exposure (or overexposure) will that be, if the base ISO is 135? I.E. how much "pull processing" will be needed, in f/stops, to compensate for the extra exposure?

 

(All this, of course, assumes the M10 follows the ISO pattern that DxO records for the M240. Which may or may not be correct.)

 

Good point, Adan.

 

In my experience with the M240/M262, ISO 100 exposes one stop above the meter setting for ISO 200. I just tried it on a tripod and it gave 1/8s for ISO 200 and 1/4s for ISO 100.

 

So effectively, since the true ISO 100 and 200  are in fact both ISO 134 according to DXOmark, the camera processor has in fact pulled the exposure by 1 stop, which makes my earlier statement about the pull being only 1/2 stop, incorrect.

[edwardkaraa]

It's interesting to see the M9 ISO measurements of DXOmark: https://www.dxomark.com/Cameras/Leica/M9---Measurements

 

Measured ISO values are closer to nominal values than the M240, but base ISO is 144.

 

So base ISO for the M240 is 134, but Leica calls it 200. Base ISO of M9 is 144, Leica calls it 160.

 

It will be very interesting to see how the M10 ISO measurements will look like.

[Steve Spencer]

It's interesting to see the M9 ISO measurements of DXOmark: https://www.dxomark.com/Cameras/Leica/M9---Measurements

 

Measured ISO values are closer to nominal values than the M240, but base ISO is 144.

 

So base ISO for the M240 is 134, but Leica calls it 200. Base ISO of M9 is 144, Leica calls it 160.

 

It will be very interesting to see how the M10 ISO measurements will look like.

 

We will know in a couple months when DXO and others do the measurements on the sensor.  If you look at the SL ISO 50 is not the same as ISO 100 and ISO 50 has a lower measured ISO and actually has better dynamic range than ISO 100, so in the way I would describe pull ISO, 50 on the SL is definitely not pull ISO. I suspect we will see the same with ISO 100 on the M10, but I think it will be hard to know for sure until we get the reports of the measurements from the sensor.

[edwardkaraa]

We will know in a couple months when DXO and others do the measurements on the sensor. If you look at the SL ISO 50 is not the same as ISO 100 and ISO 50 has a lower measured ISO and actually has better dynamic range than ISO 100, so in the way I would describe pull ISO, 50 on the SL is definitely not pull ISO. I suspect we will see the same with ISO 100 on the M10, but I think it will be hard to know for sure until we get the reports of the measurements from the sensor.

Totally agreed, Steve. ISO 50 is definitely not a pull, and measured ISO is slightly less than 1/3 stop below nominal values, so the sensor ISO performance is not enhanced by overstated numbers as in the M240. I hope the M10 will be similar.

[adan]

Where is this 'ISO 135' nonsense coming from!?

 

From synthesizing two information sources:

 

First, "5) According to Leica, the M10 base ISO is "Somewhere between 100-150 ISO". " See post #50 on this thread.

 

Second, from the DxO analysis of the M240, which tested the base ISO of that sensor as 135ish, Certainly neither 100 nor 200.

____________________

 

I still question the assumption that a hand-held meter is somehow the "gold standard" against which internal camera meters are to be judged. What it gives must be THE correct exposure, and if the M10 meter varies from that, it is the M10 meter that is "underexposing" or "overexposing." Says who?

 

Pop quiz:

 

What is the ANSI (American National Standards Institute) standard "luminance" to which all light meters are (or are supposed to be) calibrated? As expressed in "gray card reflectance."

 

1. 12%

2. 18%

3. 25%

4. 50%

[Dirk Mandeville]

I still question the assumption that a hand-held meter is somehow the "gold standard" against which internal camera meters are to be judged. What it gives must be THE correct exposure, and if the M10 meter varies from that, it is the M10 meter that is "underexposing" or "overexposing."

While I agree with your comment on a single handheld meter in general, in the example I gave in my original post on the subject Horatio Tan compared the M10 meter not just to a handheld meter, but also to the meters in a half dozen other cameras of various brands. Out of seven different camera meters and one handheld meter, the M10 was the only one that gave a significantly different result from all the others (consistently one stop over-exposed). Other sources seem to corroborate this behavior, and it may be because the sensor under-exposes relative to its camera ISO setting and the meter is calibrated to correct for this. I don't have the technical background to give a serious opinion on any of this. I just find it a fascinating discussion.

[edwardkaraa]

There is nothing unusual in my opinion about the ISO values being overstated by Leica. As far as I know, Fuji does exactly the same thing. It looks good on a spec sheet and gives the impression of cleaner high ISO.

[adan]

I have to assume Mr. Tan's other cameras did not include any of the following, which all overexposed by .7-1 stops, in my practical experience: Canon 5D/5D2/6D, Nikon D700/610/300/7100, Leica M8/9

 

Unless, of course, there is an especially bright subject within the metering area.

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[Dirk Mandeville]

I have to assume Mr. Tan's other cameras did not include any of the following, which all overexposed by .7-1 stops, in my practical experience: Canon 5D/5D2/6D, Nikon D700/610/300/7100, Leica M8/9

 

Unless, of course, there is an especially bright subject within the metering area.

I just went back and read one of his posts on the subject. Actually, he tested against eight other cameras, to wit: Leica SL, M240, M9, Sony A7rII, and Sony A7sII, Canon 5D Mark IV, Nikon D700 and Fujifilm S5 Pro. He says that if the ISO and aperture are kept the same, the M10 meter will consistently read the scene with one stop slower shutter speed than all the other cameras.

 

I don't know what the relevance of any of this is. I just thought it may have some bearing on this discussion of M10's true base ISO, so I shared it.

[adan]

Certainly useful background information. Just tried it myself with my available gear. ISO 320, f/4, metering a medium gray object (but not, apparently, exactly an ANSI gray object - see Sekonic values), lighting from 45°. 4 "meterings" done with each to check consistency.

 

Canon 6D - 1/40 sec.

Leica M9 - 1/45

Leica M10 - variable 1/30-1/45

Sekonic L-308s, reflected mode - 1/80

Sekonic L-308s, incident mode - 1/40

 

The Sekonic in incident mode, of course, ignores the tone of the subject, and just measures the incoming light, so my chosen subject gray was probably lighter than the standard of xx% gray (no one has yet responded to my pop quiz - can't give away the answer. )

 

There's also the problem of "stepped" metering readouts - my Sekonic and Canon will never show 1/45 sec, just 1/40 or 1/50. While the Leicas will never show 1/40 or 1/50, just 1/30, 1/45, 1/60.

 

And ttl camera metering is affected by lens extension factor (how close was the M10 to the subject?) and the accuracy of the specced f/stops with which metering is done (wide-open with the Canon, the shooting aperture with the Leicas).

 

A measurement is just a measurement. Science is a measurement - with every other possible variable that might affect the measurement, eliminated or accounted for.