Ad
Ad
Ad
Pages: [1]   Bottom of Page
Print
Author Topic: Canon s70 and light metering  (Read 1611 times)
Goldilocks
Jr. Member
**
Offline Offline

Posts: 88


WWW
« on: January 10, 2006, 11:33:31 PM »
ReplyReply

I'm running out of time to return the Canon s70, and I'm not sure if it does what I expected it to do. One thing that bugs me (or I can't figure it out) is how
to use the metering system so that you can see what aperture and speed
it wants to shoot at before you shoot. It seems that no matter where I
point the camera (only in Manual shows the f-stop and
speed before shooting and I'm not sure if that is the suggested settings, or settings that I have put in) the same numberts show wether I point at shadows or
hightligts, no matter wether I choose spot, evaluative, or center
weigthed (even in manual)
      There are some other related items that I'm confused about.
 I'd like to know how I can use the inbuilt light metering system to give me readings of highlights and shadows so that I know ahead of time what the difference in light
readings are within my picture and what settings will be used.
 For instance in RAW or JPEG, outside, it kept using 1/1000 of a
second and just changed the aperture, consequently blurry images (lack of depth of field) when aperture was at 2.8 for a landscape shot with foreground and
background. And I don't know this information before I take the
picture. In the above scenario, I was in Program mode on the dial. The shooting
information in the software says Program AE
Was the camera designed that way?, What am I not understanding? Or is
something set somewheres that I don't know about? Or do I have a
camera that needs to be returned because it is not working properly.
I'd appreciate if someone can get back to me asap.
If I set it to aperture priority mode, then how would I know
what speed I'm about to use before I press the button?

Goldilocks (Linda)
Logged
kenstrain
Newbie
*
Offline Offline

Posts: 23


« Reply #1 on: January 11, 2006, 03:06:00 PM »
ReplyReply

I think I have answered your questions below  

"One thing that bugs me (or I can't figure it out) is how
to use the metering system so that you can see what aperture and speed
it wants to shoot at before you shoot."

I only use my S70 in "M" (and saving in RAW) so M first, then Av.
 
I assume you've set the display mode (display button toggles it) to one that shows something on the LCD.

M - mode.
If the LCD tells me I'm way off, I adjust the shutter speed until I like what I see.  The numbers displayed at the bottom of the LCD are your choices.  The info on the LCD - the number at top left when you half press the shutter button - is the difference between your choice of shutter/aperture and the suggested exposure in EV units (-2 to 2 in 1/3 EV).  Note it only reads once each time you half-press the shutter (to do with the exposure lock function in Av mode, see below).

After the first exposure I look at the histogram (display button in preview mode allows this to be shown). If you have strongly-saturated, bright areas take care, but otherwise it should be filled nearly to the right side.
If I got it wrong I adjust.  All other exposures under the same light are then straightforward - the same!  

I nearly always set the aperture to f4  when I switch on the camera (i.e. at 5.8mm focal length) and let it drift to f5.3 on the last 3 steps of the zoom - I find that gives good quality and reasonable depth of field in all cases, but then I use other cameras for subjects where that is inappropriate).  

Now I will try Av mode.  It tells me the suggested shutter speed on the LCD (the number appears after half-press of the shutter button, and is locked until the button is released).  It is to the left of the aperture value which is always displayed in this mode (if the display is on).  If I find that the exposure is not what I want I can use the FUNC button to access the exposure compensation.  After trying that I find that M is easier!  Some people like exposure-lock, but I prefer M (on all my cameras).

"There are some other related items that I'm confused about.
I'd like to know how I can use the inbuilt light metering system to give me readings of highlights and shadows so that I know ahead of time what the difference in light
readings are within my picture and what settings will be used."

Point the camera at highlights, take a reading in Av, point at shadows, take another reading?   Not sure what you want here.

"For instance in RAW or JPEG, outside, it kept using 1/1000 of a
second and just changed the aperture, consequently blurry images (lack of depth of field) when aperture was at 2.8 for a landscape shot with foreground and
background. And I don't know this information before I take the
picture. In the above scenario, I was in Program mode on the dial."

My dial will never go to P mode, even for you!  I suggest Av mode for this
purpose   (Back to M, tape back on to hold it there!)
Wow, I forgot I had f2.8.


"If I set it to aperture priority mode, then how would I know
what speed I'm about to use before I press the button?"

See above.  If it does not show up on the display I do not understand what you are doing - I cannot avoid it on mine if the display is on at all.

EV - exposure value (equal to lens stops or factors of 2 in shutter speed).


Ken
Logged
Dale_Cotton
Sr. Member
****
Offline Offline

Posts: 580


WWW
« Reply #2 on: January 11, 2006, 06:51:18 PM »
ReplyReply

I'm going to add a bit to Ken's comprehensive response...

> I'd like to know how I can use the inbuilt light metering system to give me readings of highlights and shadows so that I know ahead of time what the difference in light

This is a job for Mr Spot Meter. Your S70 has spot metering, although like even on an expensive dSLR, any in-camera spot meter will take in too much of the scene for really accurate work, unless you are a) very close to the subject or b) are using a very long lens to get close to the subject.

Nevertheless, the formula for finding your exposure is very simple:

Spot meter the brightest part of the scene then subtract X stops
Where X = the highlight latitude of your camera's sensor


(You really don't care about the shadow reading if you are doing expose right RAW. For JPEGs the only time you might want to place the highlights anywhere but at the right extreme would be if the dynamic range of the scene is smaller than the dynamic range of the camera [technically the exposure latitude of the camera]. In that case the camera's own evaluative meter will work fine, so you don't need to spot meter.)

Now you have to find out what X equals.  On a sunny day compose a picture of a scene with glaring regions such as white clouds or the white part of houses that are in the sunlight. Looking at the in-camera histogram, change the shutter speed until the overexposure bar on the right just goes away. The number of stops you had to reduce the exposure = X; and X is probably 2.5, 2.7, or 3. Double check your answer on several other scenes.

The only way you can use aperture priority and still get a perfect exposure value without doing trial and error + histogram is to spot meter the brightest part of the scene with 3 stops of negative exposure compensation. I'd be shocked if the S70 has 3 stops negative exposure compensation.

If all the above remains confusing after a few readings, drop me a line using the e-mail facility on this forum.

I wouldn't panic about the S70: it's still got to be the best camera for your needs. Metering with a compact camera is always a trial; so is DOF. There is no camera made that is not a mixture of strengths and compromises. You already know its strengths, now you also know its weaknesses. The easy work-around is to cheat by ignoring everything above and bracket like heck.
Logged
Pages: [1]   Top of Page
Print
Jump to:  

Ad
Ad
Ad