[luiscardo]

Hi guys:

I have several Pentax film cameras and in a photo field trip with a friend, also Pentax user, we faced a problem that somehow bother us, which is the reading difference, between two cameras, measuring the light for the same scene.
Once at home we conducted a detailed experiment to quantify the difference of all our cameras, measuring with the same configuration the same landscape through a window: portion of a lake, mountains, trees, a building and some sky in an afternoon bright with some shadows (17:00 hs. or so)
ISO 400, 80mm lens (same lens always), f/11 aperture.
The "Sunny 16 rule" states for that configuration a speed of around 1/1000.

Two MZ-line cameras (MZ-5 and MZ-M), the most modern light meters we have, read 1/500. Expected due to the averaging algorithm.
A ME Super and a Ricoh KR-10 (cousing of Pentax) states 1/1000
Another ME Super goes to 1/2000
And two others, a MX and a P30t overexpose by 2ev reading a speed of 1/125

Those two were the most awkward results. In the MX I can blame the age, but with the P30t I have no explanation, cause it is pretty much the same age that MZ-ones.

Is there any answer to this?
Is this normal for you or is there any problem in some part? if so, is it easily fixable?

Ok, thanks in advance.
Bye people.


L.

[UncleVanya]

I would use a gray card and artificial lighting to first establish the baseline function. Then move to a real scene as the meter pattern and logic can be as much of an influence as anything. Negative film was far more forgiving of overexposure than digital. And unless printing your own shots the process tended to mask/minimize exposure variations of a couple of stops.

[luiscardo]

I would use a gray card and artificial lighting to first establish the baseline function. Then move to a real scene as the meter pattern and logic can be as much of an influence as anything. Negative film was far more forgiving of overexposure than digital. And unless printing your own shots the process tended to mask/minimize exposure variations of a couple of stops.

I'll take the gray card suggestion, yes yes, it was completely off my mind that resource.
I don't have a 18% card but a solid color wall would comply perfectly I presume.

I'm gonna do the same experiment with the card but so far, according to what you say, this wide results are normal (somehow).

Film is very forgiving, true fact.

Thanks.

L.

[stevebrot]

Two MZ-line cameras (MZ-5 and MZ-M), the most modern light meters we have, read 1/500. Expected due to the averaging algorithm.
A ME Super and a Ricoh KR-10 (cousing of Pentax) states 1/1000
Another ME Super goes to 1/2000
And two others, a MX and a P30t overexpose by 2ev reading a speed of 1/125

I don't see any reason for concern or awkward moments. The proof of the pudding is in the eating. Are the negatives from the MX and P30t over exposed? Are those from the second ME Super underexposed? (FWIW, a single stop difference is hard to see on a negative without using a densitometer.)

Finally...Is it safe to assume that these cameras have different lenses mounted? The readings are TTL, after all, and differences of that magnitude might be expected, particularly if there is much variation in what is actually in the frame between cameras.

Added: Lacking an actual gray card, a uniform white surface in indirect light is equivalent for simple comparison.


Steve

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Last edited by stevebrot; 11-23-2021 at 07:05 AM.

[luiscardo]

I don't see any reason for concern or awkward moments. The proof of the pudding is in the eating. Are the negatives from the MX and P30t over exposed? Are those from the second ME Super underexposed? (FWIW, a single stop difference is hard to see on a negative without using a densitometer.)

Finally...Is it safe to assume that these cameras have different lenses mounted? The readings are TTL, after all, and differences of that magnitude might be expected, particularly if there is much variation in what is actually in the frame between cameras.

Added: Lacking an actual gray card, a uniform white surface in indirect light is equivalent for simple comparison.


Steve

(And now I want to eat some pudding, thanks for the subliminal message Steve xD)
The "experiment" was only to measure through a window and taking notes using the same lens for different bodies, not even same focal lenght through different glasses, taking advantage of the K-mount we put and remove the exact same lens to minimize what you pointed out.
I don't take pics with the "experiment", but seeing the history of negatives, in general, the P30t has denser negatives than the ME Super, and you can notice it with naked eye. In general, I don't have problems with overexposed negatives coming from the P30t, the correction is not so hard, but on the other hand, in some cases I do suffer the underexposition with the ME Super.

L.

[Macario]

How did you do the test with the camera's? handheld?

the 2 modern camera's have zone metering, and like you said they do average the reading.
All the other camera's have center weighted metering. so slight other angle could give a total other reading. So for next step make sure they are on a tripod and really pointing at the same spot.

[luiscardo]

How did you do the test with the camera's? handheld?

the 2 modern camera's have zone metering, and like you said they do average the reading.
All the other camera's have center weighted metering. so slight other angle could give a total other reading. So for next step make sure they are on a tripod and really pointing at the same spot.

Hi Macario
It was handheld but you could think in a human tripod: same chair always in the same spot, my elbows supported in its armrests and the top of a chimney placed in the middle of the viewfinder. I am sure the scene doesn't change significantly by the position. Also I travel trough the bodies back and forth and did the measurements several times with repeated results.
Nevertheless, the "gray card test" with artificial light will be my next move.
L.

[Not a Number]

A gray card is the best test as you are shooting against a known and "standard" value.

Sunny 16 rule is just a guideline to get the exposure in the ballpark of being correct within the exposure latitude of the film. Ever wonder how those old Kodak Brownies with a fixed focus lens with fixed shutter speed and aperture could produce so many usable shots? Thank the exposure latitude of the film.

[andrewd]

I suspect that the cause of the overexposed readings is related to the cover of the meter cell. These can become cloudy with age.
See the blog article below. The article relates to Contax cameras but I would not be surprised if many other camera brands use the same part for the meter cell.

The Contax 139 Blog: Does your 139 over expose?

For the cameras that are underexposing, my suspicion is that this is related to the meter pattern being more or less influenced by the sky. The grey card experiment should answer that question.

[stevebrot]

The "experiment" was only to measure through a window and taking notes using the same lens for different bodies, not even same focal lenght through different glasses, taking advantage of the K-mount we put and remove the exact same lens to minimize what you pointed out.

Given your test design, you might want to consider some of the suggestions here to actually test the meters with proper constraints with a gray card or equivalent filling the entire viewfinder.

Alternatively, there is always the option of being perplexed. With the possible exception of the one ME Super, I don't believe there is a problem with any of your cameras listed.


Steve

(...many of us shoot at EI other than box speed with gray card testing as part of the process...)

[texandrews]

Well, I never really trusted my in camera meters in film days---and I had an MX. I used Luna-Pro's. My fave was the S with the Zone Dial. Had the spot attachment , too. I have a Starlight II now, But I feel like I have to reread the manual every time I pull it out. There's a lot to be said for analog, if you ask me---kinda miss my Luna Pro.

[luiscardo]

Thank you all for the insights.

Film is very indulgent with light conditions, the mercy of the latitude softness the inaccuracy of the meters and you can still have good results.
But when using the P30t in a sunny day I read 1/30 for a ISO200 was like a big WT.... (and the next letter).

Regarding what Texandrews says, I have two (cheap) hanheld light meters: a Gossen Bisix II and a Zeiss Ikon Ikophot t, both reads around 1/1000 speed but the comparison is extremely unfair because they are not spot-meters. I did it just for fun.

Anyway, the info about the cloudiness in sensors (thanks Andrewd) I think is very helpful.
Some of you said that this numbers are not to be worried about, so I'm not sure if its worth to dismantle the whole stuff to check it, but it is good to have it in mind.

Again, thank you guys.

L.

[pschlute]

I think the problem with trying to do comparisons is the age of the cameras involved. Do not forget that even when new, a specific ISO on one camera may not be exactly the same as on another

[tuco]

Hi guys:

... afternoon bright with some shadows (17:00 hs. or so)
ISO 400, 80mm lens (same lens always), f/11 aperture.
The "Sunny 16 rule" states for that configuration a speed of around 1/1000.

Summer time, mid latitudes and midday it would be f16 @ 1/1000. Higher latitudes, early/late in the day, late autumn/winter/early spring and you need to start appling adjustments to the rule. This time of year for me, my latitude, heavy deep green conifer trees everywhere on a sunny day I'd add up to 2-stops to the rule.