How E.I Calculated in SLR Camera???

[Sundar Raghavan]

Nikon Fm10-35mm Slr camera-

How ASA, Shutter speed and Aperture are interlinked in this camera to show the exposure is correct or not that is the TTL metering..

 

The camera that i have does not sense the ASA of the film which they call as Dx-code something that i am not sure.. Even when i keep wrong ASA , i have no effect in negative..

 

 

EXAMPLE- I Loaded 100ASA film and setting ASA manually in the dial, getting f-11 and shutt-1/60 as correct exposure in TTL.. When i turn ASA dial to 200 or 400 keeping same 100ASA film, it shows overexposure in viewfinder(TTL).. But it is correctly exposed in film.. And How this over and under indication in viewfinder works..

 

 

I wil also be happy if someone explain about dxcode and its working principle..

[jacob thomas]

Nikon Fm10-35mm Slr camera-

How ASA, Shutter speed and Aperture are interlinked in this camera to show the exposure is correct or not that is the TTL metering..

 

The camera that i have does not sense the ASA of the film which they call as Dx-code something that i am not sure.. Even when i keep wrong ASA , i have no effect in negative..

 

 

EXAMPLE- I Loaded 100ASA film and setting ASA manually in the dial, getting f-11 and shutt-1/60 as correct exposure in TTL.. When i turn ASA dial to 200 or 400 keeping same 100ASA film, it shows overexposure in viewfinder(TTL).. But it is correctly exposed in film.. And How this over and under indication in viewfinder works..

 

 

I wil also be happy if someone explain about dxcode and its working principle..

 

The Nikon FM10 does not read DX codes. DX codes work by having electrical contacts in the film chamber that make contact with the film cartridge (see wikipedia).

 

How are you judging whether you have the correct exposure? From prints/scans or is it reversal/slide film. Two stops overexposure might not be noticeable on prints or scans.

 

Do you have a light meter or another camera to compare the exposure with? It could be that the camera's meter is off or the batteries are flat.

[Sundar Raghavan]

I am judging exposure with the help of a spot meter in Nikon D90 and also the TTL metering... Now i am clear that Dxcode not available in my camera.. But i want to know how TTL meter calibrates exposure.. For Example- F-11,S-1/60, 100ASA is correct exposure .. Then if changing ASA alone , keeping 200ASA for f-11,S-1/60 shows over in TTL, keeping 50ASA shows Under... How this is Calibrated in Camera?? Wat is the mechanism?

[Cory Zapatka]

Sundar-

 

Just as opening up one stop allows TWICE the amount of light in, halving or doubling the ASA allows half as much or twice as much light.

 

f/2.8 lets in twice as much light as f/4

shutter speed of 1/60 lets in twice as much light as 1/120

and an ISO/ASA of 100 makes the camera twice as sensitive as 50.

 

Its a simple code in your camera that changes the sensitivity of the TTL meter.

 

Therefore, keeping your shutter speed and aperture the same but doubling or halving the ASA will make your camera read as under one-stop or over one-stop.

 

Hope this makes sense.

 

I am judging exposure with the help of a spot meter in Nikon D90 and also the TTL metering... Now i am clear that Dxcode not available in my camera.. But i want to know how TTL meter calibrates exposure.. For Example- F-11,S-1/60, 100ASA is correct exposure .. Then if changing ASA alone , keeping 200ASA for f-11,S-1/60 shows over in TTL, keeping 50ASA shows Under... How this is Calibrated in Camera?? Wat is the mechanism?