True ISO ? Have *you* checked?

[PauHana]

I would like to here from users about their experiences concerning exposure. Another professional studio photographer and I have consistently found that ISO 100 is closer to 75 or 50. My hand held meter confirms this. (Please don't weigh in on incident vs. reflective meter readings - that was taken into consideration) Do we have a couple of rare cameras that are just a bit off or is this common ?

[Topngu]

If you set Iso 100 and have ligth source EV 12 then :
ex you use M mode shutter speed at 125 what is f:
stop for correct meter? the answer :5.6....
my question is :if you have EV15 and set 1000 speed
what is correct f: stop?
How do you come up with 75 or 50 ISO,it's is one f: stop
difference!
I did check ISO...and TTL with changing difference ISO...
all come out good...i used these equipment:
S2,F100,Minolta meter IV,ZTS ligth box model V,Macbeth Color
Checker, 50mm af,35-70/2.8 af D,180/2.8 afedif.

[memobug]

PauHana

When was the handheld meter last calibrated?

Regards,

Matt

[PauHana]

Matt;

The MinoltaIV light meter was repaired and calibrated about three years ago. Its readings are accurate with two types of Ektachrome, Polaroid sheets and my Phase One digital back. It just doesn't *seem* dark on the LaCie monitor, the numbers the color picker show me its under. Having an ISO 50 chip is inconvienent but not the end of the world. My main concern is consistency and wondering if my camera is the one in a hundred that is not the indicated speed.

[Ron Green]

Oddly, I've had the same problem. Except, even manual metering yields .5 - 1 stop underexposure. Therefore I believe the problem is in the accuracy (or lack thereof) of the indicated shutter speeds. When I adjust the over/under accordingly, everthing is fine.
RBG

[picthis]

It happens sometimes that chips are off.
I shot a grey card and the checked the historygram to see if the history was in the middle. Mine was. If not then change the f stop until it is and note how off it is. If it's too far off I'd send it back

[robinchee]

with studio flash, my exposure on manual is spot on ..

[Marvo]

I've just done a job shooting street scenes on a cloudy day with S2 + Nikkor 24-85 on program mode and EVERYTHING has come out half to one stop under exposed. Studio flash metered with minolta is fine. I'm very nervous now about the TTL metering. I'm going to have to do some tests that I haven't got time for. I'll post back.

Marvo.:mad:

[Marvo]

On another note...
I've had a Minolta III for 16 yrs and a Minolta IV for 9 years.
Every transparency I shot with the III was coming back under exposed, & so were the test polaroids I shot. I sent the meter back to Minolta and it came back recalibrated but it is giving the same reading as before it went away which after extensive shooting and checking against different lab processes and different batches of ektachrome, it was apparent that the meter is 0.6 to 0.7 of a stop underexposing for BOTH ambient and studio flash sittuations, shooting with any lens on a Bronica or a Hasselblad.
I thought all of my troubles would be over when the IV came out so I got one - mucho dinero!
I couldn't believe it when I compared the two. They were exactly the same (or maybe I could believe it) ie 0.7 or two thirds of a stop underexposing. I raised it with Minolta who took the new IV back for checking and they said it was bang on. That was 9 years ago and since then I've had the meter set to 64 ASA when shooting 100 ASA trannie film (ie two thirds of a stop up) and have ALWAYS had a correctly exposed transparency when shooting the average full brightnes range subject. Have Minolta ever taken their meter out, shot a roll of trannie, processed it and looked at the pictures?
Now the S2 is giving me pictures about two thirds of a stop under!
Can anyone tell me if I'm the most unlucky guy on the planet with meters AND Minolta's calibration dept. or is everyone out there all shooting their stuff two thirds of a stop under!!!

Marvo.:(

[robinchee]

Shooting outdoors on a s2pro with no flash on P or A .. no compensation .. the exposures are spot on.. typically around iso 400 ..

[PauHana]

Marvo;

In my original post, I stated that my Minolta hand held meter was accurate with transparency film. It *IS* accurate assuming that Kodak & Fuji 100 ISO 'chrome film is 80 or 75 ! For years it has been a known fact that Kodak and Fuji rate their films as accuratly as GM and Ford rate gas mileage - kind of - sort of - maybe....... So for the past 20 years, ISO (or it used to be ASA) has been a "suggestion" to me as to where to base my exposures. When I switched to digital 2 years ago, I was hoping that an advertised exposure index was as it said it was. Those who say their exposures (with film or digital) are " dead on" may not have as critical applications as you or I. So, long answer short - you are not the only one rating film differently than the manufacturer. I am now compensating one half to two thirds over exposure with my S2.

[Mark Uehling]

Beware that the digital camera ISO will vary somewhat based on the color of the light source. As the camera adjusts for color, it adjusts the gain of the RGB channels to match the light source. This is kinda of like when you put an 80A filter over the lens, you loose a couple stops of light.

[Marvo]

Hi Mark,
Have you got any idea if the preset white balance options have built in compensation for this gain adjustment reqired under different colour temperature light sources? One would think that Fuji would have built in a correction of exposure to go with the correction of colour even under the "auto" white balance setting. ....Wouldn't they???...
From a logical point of view (which is not always the manufacturers point of view), a slight increase in noise from upping the effective ISO to compensate is much more easily suffered than an underexposed shot.
Yet more testing required I suppose!!!!

Marvo.

[PauHana]

Mark;

Excellent observation - various wavelengths would cause different responses. I wish that were the answer though - all of my tests and 75% of my shooting is done with strobes (either my Speedotrons or Metz on camera) Thanks..........