How well do u trust ur camera's metering?


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Mystix

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#1
juz curious coz i was playing ard with my eos30 manual mode and when i autofocus on a object sometimes it will show maybe +/- half stop. is it really that accurate? do i have to adjust my settings till its at 0?
me juz ventured into film based slr from a consumer digicam thats y not really sure of the metering sys. heh not used to seeing suddenly the metering system so fast.
 

#2
Take lots of pics in different kind of situations (e.g. with large part of bright sky, dimly lit room, scene with contrasty areas etc). Bracket. Make note of exposures.

After you've shot enough, you will know when to trust the meter, and when not to, and apply your own compensation by experience (and from the results of your tests).

Regards
CK
 

chyeo

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#4
I still prefer to reply on my own "metering"... :)
 

denizenx

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#5
ur own metering? lightmeter? eyemeter? haha 8P

I find my eos50 tends to value overall exposure more... hence a noon pic of armenian church framed by trees and gate will give me the nice gate and rich trees but the blue sky and church turn into the same colour-white... I think I will try to bias AE down next time... cos I suspect if I use centre-weighted it will give me black trees and gloomy gates..
 

#6
Shoot lots of slide film. Make notes. That's about the only way to learn your camera meter's bias, and when to trust/not to trust the meter. Don't use negatives for this, as you won't be able to see your exposure errors, etc as the lab will correct it.

Regards
CK
 

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Paddington

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#7
Originally posted by denizenx
ur own metering? lightmeter? eyemeter? haha 8P

I find my eos50 tends to value overall exposure more... hence a noon pic of armenian church framed by trees and gate will give me the nice gate and rich trees but the blue sky and church turn into the same colour-white... I think I will try to bias AE down next time... cos I suspect if I use centre-weighted it will give me black trees and gloomy gates..
That depends on the scene rather than your camera's metering isn't it? Slides generally have a certain fixed exposure latitude.

I trust my camera metering very much. Yah, I understand how fickle the metering can sometimes be. Same scene, but you press the shutter button 2 times you can get 1/3 stop difference in reading. But that's digital and I think in both cases the difference is very subtle. The best way is to bracket the shots.
I have posted a survey in another thread on how often one brackets.

I don't know why some pros claim they don't trust their cameras' in-built meter. For me, it works perfectly fine and it's a matter of knowing how they work in different conditions and compensate exposure accordingly. The only big problem I have now is how to ensure good exposure all the time. Bracket is ok but sometimes it's wasteful (esp for an amateur like me). There are literally millions of lighting conditions and non 18% grey situations. How do you decide then how much to compensate? Eg, 1/2 or 1 stop? Just bracket and choose the best?
 

#8
Originally posted by Paddington
I don't know why some pros claim they don't trust their cameras' in-built meter. For me, it works perfectly fine and it's a matter of knowing how they work in different conditions and compensate exposure accordingly. The only big problem I have now is how to ensure good exposure all the time. Bracket is ok but sometimes it's wasteful (esp for an amateur like me). There are literally millions of lighting conditions and non 18% grey situations. How do you decide then how much to compensate? Eg, 1/2 or 1 stop? Just bracket and choose the best?
Bracketing and experience. Meters are never 100% accurate all the time, you already said that not all scenes average out to 18% gray (13% actually, but I digress). Like I said, once you have shot enough, you will know how your meter behaves under certain situations, and you will know how much to compensate. It's not that pros don't trust their meter, just that they know when not to trust it.

The so-called "correct exposure" is also a personal preferene thing. Out of 3 bracketed shots, there can be one that you like, or all are acceptable, depending on the situation.

Film is cheap, the moment is not. Bracket if you have to, especially for things which will not happen again.

Regards
CK
 

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Paddington

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#9
Originally posted by ckiang


Like I said, once you have shot enough, you will know how your meter behaves under certain situations, and you will know how much to compensate. It's not that pros don't trust their meter, just that they know when not to trust it.
Thanks ck, agree with what u said. But the last time I attended Mr Michael Yamashita's talk, he seemed to mention (if I rem correctly) he never trusted his in-built meter. He preferred to rely on his palm. The irony is that even if you meter with your palm, you need to use the camera's in-built meter. Unless of cos you use an external light meter, which incidentally as I have found out, doesn't give the correct exposure under certain lighting conditions, eg bright sunny day. The readings are atrocious. (Think someone mentioned or asked this somewhere b4.)

The only time I find my camera's in-built meter fails is when photographing non-middle grey subjects, but that's an inherent problem with reflected light meters which our cameras use, rather than the meters not being accurate.

Yah, I did shoot a lot with slides but it never seems enough. Maybe I'm still not experienced enough after a few years? The standard grass, blue sky etc scenes are pretty easy. but if I get something tougher, eg concrete walls, in light or in shadow, it's hard to know how much to bracket even unless you are really experienced. They come in different shades, which require a wise decision on the compensation.
 

#10
Originally posted by Paddington


Thanks ck, agree with what u said. But the last time I attended Mr Michael Yamashita's talk, he seemed to mention (if I rem correctly) he never trusted his in-built meter. He preferred to rely on his palm. The irony is that even if you meter with your palm, you need to use the camera's in-built meter. Unless of cos you use an external light meter, which incidentally as I have found out, doesn't give the correct exposure under certain lighting conditions, eg bright sunny day. The readings are atrocious. (Think someone mentioned or asked this somewhere b4.)

The only time I find my camera's in-built meter fails is when photographing non-middle grey subjects, but that's an inherent problem with reflected light meters which our cameras use, rather than the meters not being accurate.

Yah, I did shoot a lot with slides but it never seems enough. Maybe I'm still not experienced enough after a few years? The standard grass, blue sky etc scenes are pretty easy. but if I get something tougher, eg concrete walls, in light or in shadow, it's hard to know how much to bracket even unless you are really experienced. They come in different shades, which require a wise decision on the compensation.
You went for the seminar as well? I was there too. ;) He claims his hands were perfectly 18%. Well, reading from your palm or a grey card for that matter, using the built-in meter is still going to be be more accurate than using the built-in meter to meter a difficult scene. That's his rationale. At least there isn't any bright lights or something to fool the meter.

For your situation, if you had bracketed all along, you'll soon find that for certain situations, you just need a certain compensation. Over time, it becomes 2nd nature. E.g. for bright snow, you will add 1.5 - 2 stops exposure, that kind of thing. The ultimate will be acquiring the skill of judging which part of the scene is "middle gray" and meter from there. If you need to, of coz, you can burn some film and bracket 2 stops on either side in 1/2 or 1/3 stop increments. ;)

Regards
CK
 

denizenx

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#11
oh I roughly can tell if the metering for negative is waaay off, ie the black is gray etc, or the white is WHITE....

can anyone tell me why ppl set film ISO lower than DX? doesn't that blow out the highlights or clouds??

external light meter is tough right when ur subject is like 50m higher than u are? eg spire of church?

as for bracketing.. not digicam quite ex lah... maybe for impt functions....
 

Zoomer

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#12
Originally posted by denizenx
oh I roughly can tell if the metering for negative is waaay off, ie the black is gray etc, or the white is WHITE....

can anyone tell me why ppl set film ISO lower than DX? doesn't that blow out the highlights or clouds??

external light meter is tough right when ur subject is like 50m higher than u are? eg spire of church?

as for bracketing.. not digicam quite ex lah... maybe for impt functions....
Cos most film deliver nicer results when overexposed by 1/3 stop. :)
 

#13
Originally posted by Zoomer


Cos most film deliver nicer results when overexposed by 1/3 stop. :)
Actually, that's not quite true. It behaves like that because most of the colour negative films are not at its rated speed, e.g. ISO 400 is actually 250 or 320. Exposing at "1/3 overexposed" actually exposes it closer to its rated speed, giving you a closer, more accurate/correct exposure. This is also known as "re-rating" the film.

Regards
CK
 

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Paddington

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#14
Originally posted by ckiang


You went for the seminar as well? I was there too. ;) He claims his hands were perfectly 18%. Well, reading from your palm or a grey card for that matter, using the built-in meter is still going to be be more accurate than using the built-in meter to meter a difficult scene. That's his rationale. At least there isn't any bright lights or something to fool the meter.

For your situation, if you had bracketed all along, you'll soon find that for certain situations, you just need a certain compensation. Over time, it becomes 2nd nature. E.g. for bright snow, you will add 1.5 - 2 stops exposure, that kind of thing. The ultimate will be acquiring the skill of judging which part of the scene is "middle gray" and meter from there. If you need to, of coz, you can burn some film and bracket 2 stops on either side in 1/2 or 1/3 stop increments. ;)

/B]


Heh-heh.. Yup, I was there too! Actually from my own experiment, a grey card is no longer grey in bright conditions. So if you use a grey card, the camera is going to give an underexposure.

Yah, I do agree it's sometimes possible to find a middle grey scene and take exposure reading from there. But suppose you are photographing a snowy landscape and you use slides. Everything's white and it's hopeless to find a middle grey. And suppose the scene is so beautiful you want to take many different angles and compositions. How? Bracket every shot 2 times, +1.5 and +2?
 

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Paddington

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#15
Originally posted by denizenx
oh I roughly can tell if the metering for negative is waaay off, ie the black is gray etc, or the white is WHITE....
Yah but that's bcos it's really waaay off. You can't learn much from negatives if your exposure is out by +/- 1 or sometimes even +2 stops.
 

tsdh

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#16
Originally posted by ckiang
Actually, that's not quite true. It behaves like that because most of the colour negative films are not at its rated speed, e.g. ISO 400 is actually 250 or 320. Exposing at "1/3 overexposed" actually exposes it closer to its rated speed, giving you a closer, more accurate/correct exposure. This is also known as "re-rating" the film.
Regards
CK
CK, the film manufacturers didn't lie, they put the ISO rating correctly. But why most negative films are better if over exposed? it is because most of them have the latitude wider at the upper end (around -2/+3). Meaning it can capture 3 stops above the correct exposure, while only 2 stops at the bottom end.
By over-exposing, let say +1, I will pull the shadows since the captured range become -3/+2.
So it is not because the actual ISO speed is different than the published one.

As for the metering, I always use the camera's spot meter (never use matrix or center-weighted, except for casual photo or fast-action photo). I meter the object/point which I want to capture correctly, it maybe portion of the object. Sometimes, I metered several points in the scene visible thru my viewfinder, so that I have an idea on how wide is the dynamic range. If the dynamic range is too wide for my film to capture, then I have to choose which to capture and which to ignore. So I know what will be captured on the film, not guessing.
 

#17
Originally posted by Paddington


Heh-heh.. Yup, I was there too! Actually from my own experiment, a grey card is no longer grey in bright conditions. So if you use a grey card, the camera is going to give an underexposure.

Yah, I do agree it's sometimes possible to find a middle grey scene and take exposure reading from there. But suppose you are photographing a snowy landscape and you use slides. Everything's white and it's hopeless to find a middle grey. And suppose the scene is so beautiful you want to take many different angles and compositions. How? Bracket every shot 2 times, +1.5 and +2?
Well, you probably know that for snow, you need to +1 to 2, depending on the lighting. For bright sunlight, add +2. If not, +1 or 1.5 should do well. Then use that to shoot all your angles. The snow should come out nice and white. If unsure, then bracket.

From the book "Confused Guide to Spot Metering" (or something like that), it's summarised as follows:

1. Pick an area and spot meter.
2. If the area is bright white, +2
3. If the area is white, +1
4. If the area is middle grey, no compensation.
5. If the area is darker than middle grey, -1
6. If the area is black, -2.

Actually, the grey card reflects 18% (or 13%, depending on which school you belong to) of the light falling on it. It not necessarily has to remain "grey". 18% of a bright sunlight is obviously different from 18% of indoor flourescent. :)

Regards
CK
 

#18
Originally posted by tsdh

CK, the film manufacturers didn't lie, they put the ISO rating correctly. But why most negative films are better if over exposed? it is because most of them have the latitude wider at the upper end (around -2/+3). Meaning it can capture 3 stops above the correct exposure, while only 2 stops at the bottom end.
By over-exposing, let say +1, I will pull the shadows since the captured range become -3/+2.
So it is not because the actual ISO speed is different than the published one.
No, the rated film speed may not be right. That's why some photographers to speed tests on their film to find out its true rating. It's pretty well known that not all films are rated at their true speed. NPH 400 for example, is said to be closer to 250 or 320. The ISO equivalency of some digital cameras are also not correct for that matter.

Regards
CK
 

erwinx

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#19
agree with Ckiang. Bracket Bracket Bracket. (and then find out the Nikon matrix gives the right exposure most of the time ;) ) Still, with 3 bracketed exposures, you can make the image even more 'perfect' by doing a 'digital ND grad'.
 

tsdh

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#20
Originally posted by ckiang

No, the rated film speed may not be right. That's why some photographers to speed tests on their film to find out its true rating. It's pretty well known that not all films are rated at their true speed. NPH 400 for example, is said to be closer to 250 or 320. The ISO equivalency of some digital cameras are also not correct for that matter.
Regards
CK
Then you can sue the manufacturer for cheating :)
If you get a film and then test it based on the manufacturer's data sheet, then it will be correct.
What happen is;
The manufacturer use test pattern with precision lab equipment to measure film characteristic, including ISO speed. While the photographers use daily objects/scene and their camera without those precision supplies. Both will result in slight difference.
Most of those photographers are not technical freaks, so simply they say the rating is incorrect, and they do adjustment.
Do manufacturers know this issue? I believe they know for long, but till today they never amend their ISO labeling, because they have good evidence to support it. (pls take note that this issue happens on most of films, not just one or two, and become a 'generic issue').

If you read my description on the over-exposing vs film latitude, then you should understand what the issue is.
 

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