In shutter-priority with exposure locked take a picture and...

[jmorton]

I was just fooling around and trying out locking the exposure using the info provided in that posted video (great video) and I took a picture.

When I viewed the picture I was pleased to see that the shutter speed of 1/48 and aperture of 5.6 were displayed but also there was a small square with the +/- sign in it: the exposure compensation symbol and the value +2.75 just to the right of it.

When I took the picture I had the exposure locked at +11 with an aperture of 5.6 and shutter speed of 1/48. So it appears to me that the +11 relates to the +2.75 as meaning that each step in the exposure as you manually increase it represents 1/4 of a stop thus +11/4 = +2.75 fstops.

Does this make sense? :hv20-smilie03:

JM

[Dodgy Nick]

Very interesting jmorton! Could you repeat the exercise with different exposure settings to see if it is consistently the exposure value / 4?

[jmorton]

"Very interesting jmorton! Could you repeat the exercise with different exposure settings to see if it is consistently the exposure value / 4?"

I just got through trying it again.

Yesterday when I tried it it was late afternoon around 5:30pm. Tonight it was about 9pm.

Yes. It does in fact work out to be the exposure compensation setting in steps (-11 to +11) / 4 = the exposure compensation displayed in the picture mode in each picture. What I think this indicates is that each step of compensation in exposure lock is equivalent to +/- 0.25 fstops.

Tonight I locked the aperture to 7.3
I took a picture at each exposure setting beginning with 0. Then I took eleven pictures increasing the exposure one step to +11. Then I went back to zero and took another picture. Then I took eleven more pictures decreasing the exposure one step to -11.

Then I went into the SD card mode. I viewed each picture and it clearly showed the exposure compensation increasing or decreasing 0.25 fstops per step throughout the entire range. But this is not reflected as clearly in the apertures displayed.

Below are some data. What is your interpretation?

JM

shutter speed is 1/48 throughout

before exposure lock on Auto: F1.8 no exposure adjustment
(the data is not displaying properly. There are three columns. The first column is Range. The second column is Exposure Compensation. And the third column is fStop.)

Range Exposure fStop
Compensation
-11 -2.75 F19.0
-10 -2.50 F17.0
- 9 -2.25 F16.0
- 8 -2.00 F15.0
- 7 -1.75 F14.0
- 6 -1.50 F12.0
- 5 -1.25 F11.0
- 4 -1.00 F10.0
- 3 -0.75 F9.5
- 2 -0.50 F8.7
- 1 -0.25 F8.0
0 0.00 F7.3 locked
+ 1 +0.25 F6.7
+ 2 +0.50 F6.2
+ 3 +0.75 F5.6
+ 4 +1.00 F5.6
+ 5 +1.25 F5.6
+ 6 +1.50 F5.6
+ 7 +1.75 F5.6
+ 8 +2.00 F5.6
+ 9 +2.25 F5.6
+10 +2.50 F5.6
+11 +2.75 F5.6

[tootom]

Range Exposure fStop
Compensation
-11 -2.75 F19.0
-10 -2.50 F17.0
- 9 -2.25 F16.0
- 8 -2.00 F15.0
- 7 -1.75 F14.0
- 6 -1.50 F12.0
- 5 -1.25 F11.0
- 4 -1.00 F10.0
- 3 -0.75 F9.5
- 2 -0.50 F8.7
- 1 -0.25 F8.0
0 0.00 F7.3 locked
+ 1 +0.25 F6.7
+ 2 +0.50 F6.2
+ 3 +0.75 F5.6
+ 4 +1.00 F5.6
+ 5 +1.25 F5.6
+ 6 +1.50 F5.6
+ 7 +1.75 F5.6
+ 8 +2.00 F5.6
+ 9 +2.25 F5.6
+10 +2.50 F5.6
+11 +2.75 F5.6


Hi jmorton,

from -11 to 0 your explanation is right: compensation step = 0.25 fstop. This is also show by the fstop-values.
From +3 to +11 the aperture stays at 5.6, but I'am sure the exposure in your pictures has changed! (according to compensation step = 0.25 fstop like above in your table) Here the exposure is contolled by the internal ND-filter, which is variabel with a range of 2.5 fstops.

For futher expanation see "blur by diffraction" under "camcorder information".
With "full aperture step" I meant fstop and with "correction step" compensation step. My german english is getting better ;-)


tootom