ESP vs Spot Metering?

smithaa02 wrote:

So I'm familiar with the basics of ESP vs Spot. But I am more curious to know the nuances of spot metering (especially on the TG series).

Can you achieve identical results between the two by merely adjusting EV? Or does spot metering do other hidden things under the hood?

It depends on the scene lighting. ESP mode meters at the center of the scene and applies a slight bias towards the light value found there. But, it also evaluates the rest of scene and attempts to come up with a exposure to balance the brightest areas with the darkest ones. If the scene has perfectly flat lighting, the ESP and Spot metering values will be pretty close. It doesn't make any sense to use spot metering then change exposure to the evaluative value.

My problem with the TG series spot metering mode is it uses a fairly small area. I only use it when it makes sense. Wished a center weighted mode was offered.

Why would you think spot mode changes other parameters? It's just limits where light levels are measured.

- Does spot metering have different focus method (relative to ESP)?

No, the 2 functions are independent of each other.

- Will spot metering result in a different AWB calculation?

AWB attempts to determine the color temperature of the light source. It needs to evaluate the entire scene. But if metering causes clipping in any of the color channels, white balance calculations will probably be corrupted.

- Will spot metering affect contrast?

No

Also does spot metering affect the black point?

No, that's a function of the JPEG engine. It doesn't care how the scene was metered.

When I change the EV, usually the blacks stay black. But this doesn't make sense if I'm changing SS/ISO/A. Shouldn't the blacks change to say a dark grey with more light? I assume then that Olympus changes their contrast algorithm to compensate for what the sensor provides. If this is the case, then do black points change for spot metering?

If you use positive compensation, the blacks will move up in level. It's a global adjustment. But the JPEG engine will squeeze those darker values into a fairly small range of the tone curve. Again, the JPEG engine doesn't consider what metering method was used.