Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-06-2008, 09:20 PM   #1
Veteran Member
FHPhotographer's Avatar

Join Date: Jul 2008
Location: Fountain Hills, AZ
Photos: Gallery | Albums
Posts: 1,298
what don't I get about exposure?

After months of trying to learn, I guess I still don't understand exposure, or at least how the K100D "thinks" about exposure. Here are two examples, shot under the same conditions and both with a reading of 3@f/2.8 (0 EV), yet the first was a spot meter reading on the dark avacado and the second was a spot on the very bright banana. How can the meter "see" the same picture when it's focused on such very different bright/dark objects? One or the other should be under or over exposed, right? Or maybe not,




FHPhotographer

09-06-2008, 09:51 PM   #2
Senior Member




Join Date: Jan 2008
Location: Barrie, ON
Photos: Gallery
Posts: 174
I dont think that the "spot" metering is as small as we think it is. It looks like that the two objects overlap in the centre of both pictures. And the light source was not changed, and in my mind, the shutter speed, if it did need to be changed, would be minimal. I might be thinking incorrectly though.
09-07-2008, 02:10 AM   #3
Inactive Account




Join Date: Nov 2007
Location: Scotland, UK
Photos: Gallery
Posts: 37
I think Ghost has it nailed. Try it with the fruits separated you will get different results.



Mick
09-07-2008, 04:32 AM   #4
Senior Member
chrisman's Avatar

Join Date: Jan 2007
Location: Sydney
Photos: Gallery
Posts: 237
PhotoMe reports that both photos were shot with exposure set to Manual and both at f2.8. This would account for the exposure being identical in both shots.

Your focus however was set for Spot. This can be seen by comparing the depth-of-field in both photos - the second one is focussed on the banana.

I have not used a K100D, only a K10D, but you need to set the exposure to Spot, not just the focus.

09-07-2008, 08:08 AM   #5
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,314
I can't comment on how you metered, and how you made the shutter and apature settings, but in looking at the exif data, you are in manual mode, so unless you press the green button to set the metering to the new scene you will not have changed your camera's settings.

Manual means just that manual.
09-07-2008, 11:28 AM   #6
Senior Member




Join Date: Jul 2008
Location: NC USA
Photos: Gallery
Posts: 251
You shouldn't mix bananas with avocados...
09-07-2008, 12:46 PM   #7
Veteran Member
FHPhotographer's Avatar

Join Date: Jul 2008
Location: Fountain Hills, AZ
Photos: Gallery | Albums
Posts: 1,298
Original Poster
No green button response

QuoteOriginally posted by Lowell Goudge Quote
I can't comment on how you metered, and how you made the shutter and apature settings, but in looking at the exif data, you are in manual mode, so unless you press the green button to set the metering to the new scene you will not have changed your camera's settings.

Manual means just that manual.
Sorry, I don't have a green button on a K100. Now what?
FHPhotog
09-07-2008, 12:50 PM   #8
Veteran Member
FHPhotographer's Avatar

Join Date: Jul 2008
Location: Fountain Hills, AZ
Photos: Gallery | Albums
Posts: 1,298
Original Poster
Ah but they make a wonderful salad...

QuoteOriginally posted by jocko_nc Quote
You shouldn't mix bananas with avocados...
...they're both fruits, so if you slice and dice one of each, add some julienned jicima, fresh grind a few cumin seeds and toss with a touch of olive oil and fresh lime juice, and serve on a fresh romaine leaf, you get a wonderful summer salad.
FHPhotog

09-07-2008, 12:54 PM   #9
Veteran Member
FHPhotographer's Avatar

Join Date: Jul 2008
Location: Fountain Hills, AZ
Photos: Gallery | Albums
Posts: 1,298
Original Poster
Maybe that's the problem...

QuoteOriginally posted by chrisman Quote
PhotoMe reports that both photos were shot with exposure set to Manual and both at f2.8. This would account for the exposure being identical in both shots.
Your focus however was set for Spot. This can be seen by comparing the depth-of-field in both photos - the second one is focussed on the banana.
I have not used a K100D, only a K10D, but you need to set the exposure to Spot, not just the focus.
You're right about the exposure... but I thought exposure was set to the AF point, and maybe that's the problem? Is there anybody out there using a K100 who can help me out with this? Thanks,
FHPhotog
09-07-2008, 03:36 PM   #10
Veteran Member
Mike Cash's Avatar

Join Date: Jan 2007
Location: Japan
Photos: Gallery
Posts: 6,952
If you're in Manual mode, exposure is set to whatever the hell the photographer sets it to. Lots of folks seem to overlook that, somehow.

So of course you get the same settings if all you did was to shift the camera a bit. You could have picked it up, taken it outside, and pointed it at the sun and you would have gotten the same settings.

You should have done this in either Av or Tv mode if you wanted to see what sort of difference it would have made in exposure.
09-07-2008, 05:09 PM   #11
Veteran Member
FHPhotographer's Avatar

Join Date: Jul 2008
Location: Fountain Hills, AZ
Photos: Gallery | Albums
Posts: 1,298
Original Poster
I never thought of that...

QuoteOriginally posted by Mike Cash Quote
If you're in Manual mode, exposure is set to whatever the hell the photographer sets it to. Lots of folks seem to overlook that, somehow.

So of course you get the same settings if all you did was to shift the camera a bit. You could have picked it up, taken it outside, and pointed it at the sun and you would have gotten the same settings.

You should have done this in either Av or Tv mode if you wanted to see what sort of difference it would have made in exposure.
Mike, I'll take as an article of faith that you're giving me the straight poop on this, but to a novice it seems counterintutive: the camera light meter isn't linked to the settings, or the rendered image, and I don't need it except to tell me if it thinks the settings I've chosen are under/over exposed . I suppose a good term would be that the lightmeter (in Manual) is uncoupled from the image?

And...now that I type if out, it makes sense that manual means manual . That's a tough swim upstream against the notions that a novice comes into this with. Thanks, I think....
BHPhotog
09-07-2008, 05:24 PM   #12
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by FHPhotographer Quote
to a novice it seems counterintutive: the camera light meter isn't linked to the settings
Of course it is. But in manual mode, the meter doesn't *do* anything except tell you how under- or over- exposed it thinks the picture will be with the current settings. It won't actually try to fix the problem for you until you hit the AE-L button (which is the K100D equivalent of the Green button in this context).

BTW, despite our preconceived notion that the avocado is dark and the banana light, in the grand scheme of things, they are not actually all that different - both are considerably darker than the background, and the lightest areas on the avocado are actually no darker than the darkest areas on the banana. So depending on *exactly* where your spot meter is pointed, it is not actually unreasonable that the meter would suggest the same exposure in both cases.

QuoteQuote:
I suppose a good term would be that the lightmeter (in Manual) is uncoupled from the image?
If you had looked at the display to the right side of the viewfinder, you'd have noticed it telling you whether it thought the exposure was too bright (positive numbers), too dark (negative numbers), or right on (0.0). At least, for lens that support auto-exposure. With manual exposure lenses (ones with an aperture ring not set to the "A" position), you only see that display while holding the DOF preview button.
09-07-2008, 05:24 PM   #13
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,314
QuoteOriginally posted by FHPhotographer Quote
Sorry, I don't have a green button on a K100. Now what?
FHPhotog
I believe on the K100 (all single thumbwheel dslrs) it is the AE-Lock button while in manual mode, or to see the meter reading (over / under exposure) use the DOF preview (the on off switch pulled past on)
09-07-2008, 05:35 PM   #14
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,231
QuoteOriginally posted by FHPhotographer Quote
Mike, I'll take as an article of faith that you're giving me the straight poop on this, but to a novice it seems counterintutive: the camera light meter isn't linked to the settings, or the rendered image, and I don't need it except to tell me if it thinks the settings I've chosen are under/over exposed . I suppose a good term would be that the lightmeter (in Manual) is uncoupled from the image?

And...now that I type if out, it makes sense that manual means manual . That's a tough swim upstream against the notions that a novice comes into this with. Thanks, I think....
BHPhotog
Yep, manual means manual. It is just as manual as my old Ricoh Singlex TLS with the meter switch turned off. When you are in M mode your meter essentially does nothing unless you purposefully inject it into the process by pressing the AE Lock button (I think that is how it works on the K100D). This stops down the lens momentarily and allows the meter to see the same light that the detector sees. It then applies its best estimate of good settings and turns itself back off. You are then free to modify the settings as suits you.

Steve
09-07-2008, 06:02 PM   #15
Veteran Member
alohadave's Avatar

Join Date: Jan 2008
Location: Quincy, MA
Photos: Gallery | Albums
Posts: 2,024
QuoteOriginally posted by stevebrot Quote
Yep, manual means manual. It is just as manual as my old Ricoh Singlex TLS with the meter switch turned off. When you are in M mode your meter essentially does nothing unless you purposefully inject it into the process by pressing the AE Lock button (I think that is how it works on the K100D). This stops down the lens momentarily and allows the meter to see the same light that the detector sees. It then applies its best estimate of good settings and turns itself back off. You are then free to modify the settings as suits you.

Steve
It doesn't even stop down the lens since the lightmeter knows what the aperture is set to and can calculate the correct exposure (assuming that it's not a manual lens). What pressing the AE-L/Green button does is calculates what the camera would choose as the optimal aperture/shutter combination based on the pre-programmed exposure curve.

The camera has a set of aperture/shutter speed combinations that it selects based on the available light, this is called the program line. Pressing the AE-L/Green button activates this program and overrides your manual settings. It's like switching into P mode for a second without moving any dials.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dslr, exposure, meter, photography, spot
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Nature Don't Feck With Me! donallison13 Post Your Photos! 1 11-02-2010 09:10 PM
Nature Don't Feck With Me! donallison13 Post Your Photos! 1 11-02-2010 06:27 PM
HI,I'm Don Dryer d-dryer Welcomes and Introductions 3 11-10-2009 07:47 PM
Don Neal donneal Welcomes and Introductions 2 01-25-2009 05:10 PM
Don in Louisville craftsmansky Welcomes and Introductions 3 10-28-2007 04:21 AM



All times are GMT -7. The time now is 02:25 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top