Q exsposure

[matlep]

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Need help here. Wouldn't at Q set to the same ISO, shutter and aperture as an M result in a similar exposed picture?

 

Using the cameras side by side, I seem to get pictures that are brighter with the Q compared to the M. (262)

 

I was under the impression they would be similar? It is almost like one stop brighter from the Q.

 

Any insight?

[Bart van Hofwegen]

Need help here. Wouldn't at Q set to the same ISO, shutter and aperture as an M result in a similar exposed picture?

 

Using the cameras side by side, I seem to get pictures that are brighter with the Q compared to the M. (262)

 

I was under the impression they would be similar? It is almost like one stop brighter from the Q.

 

Any insight?

 

In theory, they should be similar. In practice, this rarely happens. A major cause is different transmission factors between lenses (T-stop). Good light meters can be calibrated for T-stop to get to correct exposure at large apertures. Also, angle of light leaving the lens and the sensor design come into play, among many other things. Some camera makers secretly "boost" ISO at larger apertures because of this. Maybe Leica does so for the Q, since its lens fixed and the "correction" is therefore also fixed, but not (or less so) for the M. Or maybe the Q has a very good T value compared to the M lens you used. Or both.

 

Have you tried different lenses on the M, as well as smaller vs larger (fully open) apertures? That should be interesting.

 

Check out https://luminous-landscape.com/an-open-letter-to-the-major-camera-manufacturers/ for instance, but much more about this can be found on the Internet. You are not alone... 

[matlep]

Thanks Bart! I suppose Leica does some tricks with the Q that we as users have no control of. Boosting exposure is probably most likely.

[Bart van Hofwegen]

Thanks Bart! I suppose Leica does some tricks with the Q that we as users have no control of. Boosting exposure is probably most likely.

But please note that it could be any combination of things. Even if Leica does not boost ISO, and sensors would be the same, but the Q lens has a faster T than the M lens you used, shooting at f/1.7 would yield greater exposure on the Q and this would be perfectly logical. Changing lenses on the M should then change this behavior. There are plenty of other factors at play in this game, however.

 

This is why I do not use external light meters anymore since the advent of digital. I try to learn to understand the behavior (and quirks) of the metering of every camera I use, in different situations, to be able to predict when it is wrong and to use compensation. The in-camera meter meters the value as seen through the lens and is typically more or less properly calibrated to the sensor. When in doubt, I shoot brackets. Saves carrying (expensive) equipment around also...

[matlep]

At the moment I only have one lens for the M. I compared exposures using the same setting f 2.8 if I remember correctly.

[Bart van Hofwegen]

At the moment I only have one lens for the M. I compared exposures using the same setting f 2.8 if I remember correctly.

Well, if that is also the largest opening for that lens, then the T stop is probably at least 3 and usually greater. I have seen T/3.8 at times, and not even just for the cheapest lenses. The Q at f/2.8 is probably very close to a real value of 2.8. So there is a possible difference already.

[matlep]

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Thanks for the input! The lens is a Zeiss 35 2.8 so it is a cheapie!

[matlep]

Things I did not know.

[Bart van Hofwegen]

Things I did not know.

Thanks, glad I could make a contribution. Please note that this only applies to exposure. DOF is a function of F-stop and has nothing to do with T-stop at all. So reducing DOF is a perfectly valid reason to open up the aperture fully even though the exposure may not change as much as you expected (or even not at all). It is the latter phenomenon that some camera makers "correct" for by silently boosting ISO when opening up. But if you are aware of the T-stop of the lens you use, it would be better not to do that. In fact, that could be a way to become aware of this in the first place. I think full control over exposure is always better, even if it does not work like one expects at first glance. I do not know if Leica does this, and it hardly matters for most real life pictures, but your experience with the M seems to indicate that they do not, at least not for Zeiss lenses. Was the M picture underexposed? 

[matlep]

Yes, I think it is more likely that it is the M picture that is underexposed rather than the Q overexposed.

[Bart van Hofwegen]

Yes, I think it is more likely that it is the M picture that is underexposed rather than the Q overexposed.

Then indeed it would seem that the difference in transmission values is the cause. You metered the scene and dialed in values for a certain ISO/shutter speed combo for a fixed f/2.8 aperture. Both cameras are therefore set for the same amount of light but the M + Zeiss 2.8 simply receives less due to lower transmission of the Zeiss lens at f/2.8 than expected.

[Guest]

Then indeed it would seem that the difference in transmission values is the cause. You metered the scene and dialed in values for a certain ISO/shutter speed combo for a fixed f/2.8 aperture. Both cameras are therefore set for the same amount of light but the M + Zeiss 2.8 simply receives less due to lower transmission of the Zeiss lens at f/2.8 than expected.

 

This discussion has overlooked the possibility the the metering mode in both cameras is different ... on the Q was it set for spot center weight or matrix ... exposure off the shutter in Leica RF is based on the center weighted spot and its sample size varies with focal length ... longer length gives a smaller spot

so it approaches more of a spot meter.

 

External meters can now be calibrated to each digital camera and sensor in use to eliminate some of the inconsistencies found in metering. Sekonic uses software and samples to measure the delta from the ideal and applies a correction. This value is retained in meter in attempt to approach a consistent value

independent of camera of choice ... once calibrated to the camera.

 

Transmission values should not be a source of difference if the in camera meters are calibrated to a standard and are sampling the same point and area of light. This is rarely the case and much more likely the difference in values .... middle gray is middle gray ... a good workaround is to meter grass or blue sky away from the sun 

- large areas of equivalent values that should give a similar response ... not reading as the corrections in camera should lead to similar exposures. Or use a grey card and map each camera .... Q and the M with your lens to apply the necessary correction ... i.e. increase the EC in the M if it is underexposed ... and compare both

at a range of apertures.

 

Similar to the old days of exposing each batch of film to find its ideal ISO based on your exposure and processing.

 

However ... one stop difference should be somewhat amenable to correction in post unless you have blown highlights or severely underexposed at a higher ISO.

 

 

Bob

[Bart van Hofwegen]

This discussion has overlooked the possibility the the metering mode in both cameras is different

No, metering has nothing to do with it. The OP had set both cameras to the same ISO, shutter speed and aperture (so, in manual). The M picture was darker and underexposed when compared to the Q. That triggered the question why that happened.

 

So, had the metering been used, then the M would probably have set a higher exposure to compensate, and both would probably be closer. And most probably not equal due to metering differences, I agree with you on that.

 

And yes, pushing in post is doable sometimes (however not optimal). Pulling is better, but indeed, as you say, not when you have blown relevant highlights.

[Guest]

Missed the manual part of it. My bad 

 

 

Bob

[Bart van Hofwegen]

Disagree .... if the M were set to classic metering and the Q to spot then I can see multiple scenarios where the M would underexpose ... say due to a bright background or sky and the Q would measure something in the scene at a very different value. Without 

a picture and knowledge of the metering method we are both guessing ... which is why fora are so much fun.

 

 

Bob

Yes fora are fun!

 

But really: measuring did not play a role, exposure was fixed at one set of ISO/Aperture/Shutter speed. All three the same for both cameras. The meter had nothing to adjust and was reduced to an indicator. The camera had no way of influencing any other variable, as there are none. So nothing could be compensated by the M (or the Q). I presume that the meter on the M would show underexposure, yes, since it meters (I assume) through the lens. But it could not do anything, not alter any setting.

 

Think of a two cameras without meters:  one with the f/1.7 lens of the Q and one with the Zeiss f/2.8. Set both manually to ISO 100, shutter speed 1/100 and f//2.8 (that is the key here), so the same exposure. The same amount of light is expected. Now, the picture from camera with the Zeiss will be darker... How come? That was the question. Even without meters in the cameras, this sill holds. 

[jaapv]

The whole discussion misses that sensor ISO is a somewhat moving target. Whilst film ISO is defined by densities, and thus fixed by the ISO norm, it turned out to be impossible to get beyond an equivalence to film results for sensors. Thus the ISO norm for digital leaves quite some leeway for sensor manufacturers to define their own sensitivity. It should surprise no one that different sensors require different exposure to arrive at a similar results.

This has been known for years, with clear differences between Leica and Canon, for instance.

[Bart van Hofwegen]

The whole discussion misses that sensor ISO is a somewhat moving target. Whilst film ISO is defined by densities, and thus fixed by the ISO norm, it turned out to be impossible to get beyond an equivalence to film results for sensors. Thus the ISO norm for digital leaves quite some leeway for sensor manufacturers to define their own sensitivity. It should surprise no one that different sensors require different exposure to arrive at a similar results.

This has been known for years, with clear differences between Leica and Canon, for instance.

Yes, you are right of course. That is another variable in the whole exposure workings. One of many. This is why I tried to be careful and used "could" and "possibly" and such.

 

And then manufacturers seem to change sensitivity on the fly behind your back too, while keeping the ISO display in the viewfinder the same. In practice, you have to get used to specific camera/meter/lens combination behavior. Add Nikon to your list as well, my D810 does things that are hard to grasp sometimes...

 

That is why the whole discussion is no more than theory and speculation in this specific case, for the lack of more material for comparison. But I also have seen plenty of T-stop vs F-stop difference issues and it is worthwhile to know about it. And if it is sensitivity in this case, then the Leica Q and M would be different. Possible, but something else than Canon vs Leica. And, effects could add up, or cancel each other out.

 

A very good question would be if all this really matters that much in practice. It could in some situations, but once you are aware of it, you can mitigate it and be done with it, and start shooting pictures.

[Iduna]

Jaap, that is it.

The sensor development is essential and working together with the fixed lens this interplay of the Q  will always give different results than with similar parameters of any other combo. My Canon 5DMKIII is totally different than my MKII with the same lenses and gives significantly different results than my Q even if I apply the same parameters. So each one has its own special look and here creativity begins. 

[Bart van Hofwegen]

 So each one has its own special look and here creativity begins. 

Maybe. How an image finally "looks" is only partly dependent on exposure, the original subject of this thread. What the sensor captures is of course just the first step. Then you have to struggle with tonal and color response and stupid software vendors who think they got it covered. 

 

But the fact that I have to adapt to different camera and software behaviors to create or come close to the image that I envision beforehand can also be a hindrance at times... A hindrance to creativity so to speak. It has always been like that, film was no exception, but the camera was much less important then.

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Hallo,

Look here: Leica Q

[matlep]

Yes, sensors may differ for different brands, but I was under the impression that the M262 sensor and the Q sensor was very much the same animal. But that is probably not true.