Metering modes - not much difference ?

Having tried out all the metering modes - spot, centre etc, I must admit that there doesn't seem to be a great deal of difference.

Spot metering in particular doesn't seem to produce the results I expect - anyone else have any thoughts on this ?

thanks

simon

well that deppends very much upon what you expect.

At the end of the day, all three are designed to achieve the same end - to aid you in selecting the correct exposure for your photograph.

Metering is based upon the assumption that the average over the metering area will be a mid tone. For many images, this a fairly valid assumption, and the first metering systems simply applied this assumption directly. The whole scene was considered equal and an average brightness reading was used to determine the correct exposure.

Over time, various improvements have been applied to this system, to give a better "hit rate" of correct exposures. There are three modes present in the K10D, as you have observed, and they work as follows:

1. Pattern metering (is that the correct Pentax term? I get lost) - This is Pentax's most advanced metering mode. It splits the scene into 16 segments and uses cunning cleverness of which I have no real knowledge to decide how to weight those segments in its readout.

2. Centre Weighted Average - This was the forefunner of pattern metering. It assumes that the object of interest is somewhere near to the centre of the scene, so the reading is biased towards the reading from the centre. Note that the outside is still used, it is simply given a lower weighting.

3. Spot Metering - This mode is reserved for really hard lighting situations and will probably usually be used in conjunction with manual exposure (indeed on some older Pentax bodies the only way to engage spot metering was to first engage M mode). Metering is performed considering only a small spot in the centre of the scene, and the rest is ignored. On the K10D, the spot metering area corresponds roughly to the size of the central circle in the viewfinder.



If you point all three modes at a low contrast scene which really is roughly even brightness throughout, you'll get the same result from all three.


If, on the other hand, you select a complex scene with wide tonal variation then you will get different results. Spot metering particularly should give you a wide variation of meter reading as the spot moves from bright to dark areas

Thanks for the explanation but to be honest I'm very familiar with the cameras functionality - spent hours pouring over the manual when I first purchased it

The main reason for my post is that I sometimes shoot in High contrast lighting and previous to owning the GX10 (K10D) I always used Spot Metering as "average metering" didn't achieve the exposure I required.

With the GX10 I don't find spot metering producing greatly differing exposure even in high contrast scenes - I now almost always use "Pattern".

To be honest Pattern actually works very well in most instances - maybe the "average" metering of the K10D is just so much better than my previous camera that it copes with high contrast scenes more effectively. Not complainng but just making the observation really

thanks

simon

Mongoose, you are fast becoming a master of clear and concise elucidations of often complex questions.

Can we assume an academic career awaits you?

Keep it up, prof.

G

Thanks George, that's very kind. Now, if only I could convert my understanding of the technology into photographic ability!

Simon, it is my experience that whatever Pentax pattern metering actually does works extremely well in almost all situations. My K10D tends to stay on pattern almost all the time.

They say a picture is worth 1000 words, so here is a 4000 word essay These are terrible photographs which I just snapped to demonstrate the difference between pattern and spot metering. All taken with the K10D and kit lens.




This is the pattern metering shot. You could argue that it's a touch underexposed, but it's broadly speaking correct. The important thing to note is that the meter reading remains constant if I change the composition while keeping similar proportions of wood, phone and wall.




Now I have flicked over to spot metering and changed the composition very slightly. The spot is on the table, which is slightly darker than a mid tone. The camera pulls up the exposure to brighten the table and the scene ends up slightly over exposed.




Moving again so that the spot covers the phone, we get a more drastic overexposure to try and bring the black phone up to mid grey.




finally putting the spot on the cream wall causes some underexposure to bring the brightness down to mid grey.

If I leave the camera on pattern mode, then none of these three is enough of a change in the composition to change the meter output at all, while in spot mode going from the phone to the wall gives a change of 3 full stops.

I hope this little demo helps to show what difference it's supposed to make. I certainly agree that in most situations pattern metering is your best option.

Mongoose

What are the lottery numbers going to be this Saturday ?

6 13 26 31 35 and 42

I've been using centre weighted metering on my K10d as the default method after finding that the 16 segment metering option gives me a higher proportion of underexposed shots than expected. I'm actually disappointed in the segment metering mode. However its no real problem because there is always a solution. Any shot with more than a 20% proportion of bright cloud in it always appears underexposed with straight forward segment metering. If I take a traditional landscape shot with centre weighted it appears ok. Take the same shot with the segment metering and it appears underexposed unless I use a graduated ND filter.

That's my current experience with the metering modes.

I agree, and I'm suprised that Simon doesn't find a "great deal of difference". As Mongoose's examples prove, there can be a significant difference between the three modes.

Thanks. i've bought the ticket

lol, well if you win I expect a cut

Mongoose

Apart from the stray "bonus ball" your prediction was utterly hopeless. I am afraid you have dropped a few notches from "Master of all knowlege".

But hey, even gurus have their off days I suppose.

Curses! bang goes another Nobel prize! back to the drawing board I suppose......