Learning to shoot in Manual mode.

[kiranshankar]

Hello All,

 

I am trying to get used to shooting in Manual mode. I also purchased the book

'Understanding Exposure' by Bryan Peterson and I am in the process of completing

the exercises mentioned in the book.

I have one question while learning the ISO I noticed that in the book it is

mentioned that when you increase ISO from ISO 100 to ISO 200. The shutter speed

changed from 1/125sec to 1/150 sec in the view finder ( even though in the book

it is mentioned that they are just examples) On my XTI i was never able to get

that kind of shutter speed. The shutter speed which was displayed for me was

like 0.6" and 1.3" ( I was tryin to aim at a subject under fluroscent light). I

would like to know If there is some converson for 0.6" and 1.3" ?.I searched the

XTi manual and i could not find any information regarding that.

 

 

- Kiran

[mendel_leisk]

0.6" and 1.3" are:

 

"6/10" and "1 and 3/10" seconds.

 

Canon shows fractions such as one quarter of a second or smaller in the traditional way, displaying the number in the bottom of the fraction. For example:

 

1/4, 1/8, 1/15 display as:

 

4, 8, 15 respectively.

 

But any shutter times longer than 1/4 second, the display reverts to that decimal of a second format. I do not like it myself, find it hard to understand, and end up checking the manual again-and-again for these.

 

BTW, if you're getting these greater than 1/4 second exposure times, and are hand-holding the shot, you need to raise your ISO a few steps, until you get back to at least "15" (1/15) of a second exposure time. Try 1600 for starters. Or get into some brighter light.

[charliexia]

"-means seconds. so 0.6" means 0.6 seconds and 1.3" means 1.3"

when you increas you ISO by one stop your shutter speed should twice as fast. ceteris paribus. so if at ISO 100 your shutter speed is 1.3" and you switch your ISO to 200, keeping apature, focus and the metering consistant your shuttery speed should be about 0.6"

[leopoldstotch]

<p><i>"...increase ISO from ISO 100 to ISO 200. The shutter speed changed from 1/125sec to 1/150 sec in the view finder ( even though in the book it is mentioned that they are just examples) On my XTI i was never able to get that kind of shutter speed"</i></p>

<p>You didn't get shutter speeds like that because there wasn't enough light. Shutter speeds are not constants, and to get correct exposure, they will change depending on how much light is available, and which aperture you use. I'm sure if you keep reading the book, it will become clear.</p>

[brad_w]

0.6" means that the shutter is open for six tenths of a second. " is a common abbreviation

for seconds. Shutter speeds and aperture values are rounded off to a single decimal place,

so a shutter speed of 1.3" means that the shutter is open for twice as long as 0.6". In

other words, the sensor is receiving an additional stop of light.

 

Changing ISO from 100 to 200 acts similarly - the sensor is twice as sensitive to light at

200 than at 100. So - assuming that the aperture value is constant - shooting at ISO 100

and 1.3" shutter speed yields the same exposure as ISO 200 and 0.6".

 

If you're working in manual mode, changing ISO does not automatically change shutter

speed. If you're indoors shooting directly at a light source, the contrast of the scene will

be very high - there is a large difference in brightness between the darkest and lightest

parts of the frame. In these sitauations, multi-segment metering will be very sensitive to

the exact position of the light source in the frame, and varying the composition slightly

will make the computer choose a different exposure. That's why the exposure appears to

be "off" by 2/3 of a stop in the example you gave: 1/150 at ISO 200 instead of the

expected 1/250. (I'm assuming "150" is not a typo.) Solution: be sure you are using

center-weighted or spot metering. In those modes, the camera/computer is not making

any guesses about which parts of the scene it thinks that you want exposed properly.

don't think the Rebels have spot metering, however. If you are already using center-

weighted metering, and still having this problem, use a tripd to ensure consistent framing.

 

-B

[kiranshankar]

Thanks for the response. I was just trying to try out the exercise part mentioned in the book. I probably did not get the same shutter speed as mentioned in the book because i was shooting under flouroscent light i guess.

[leopoldstotch]

I think the point of that excercise was to help you realize the effect raising ISO has on shutter speed (I.E. Double the ISO, Double the shutter speed). Getting the same shutter speed as the book is irrelevant, it was just an example meant to teach you what raising ISO will do.

[brucecyr]

"when you increase ISO from ISO 100 to ISO 200. The shutter speed changed from 1/125sec to 1/150 sec in the view finder"

 

Surely you've made a typo. Also you should review that material again thoroughly until you understand why raising the ISO from 100 to 200 will NOT change the shutter speed from 1/125sec to 1/150sec. What should the second shutter speed be?

[kiranshankar]

At this point of time all i remember about ISO is he compares it to worker bees. So 200 workers bees can do the work quicker than 100 worker bees :) which means when i change ISO from 100 - 200 the shutter speed to should be less compared to what it was for ISO 100. Did i get that right?

[brucecyr]

"Did i get that right?"

 

Half a point. For a full point, figure out the exact expected shutter speed assuming all other factors are equal.

[tdigi]

Yes I agree that it gets confusing as you get into the seconds. For most shots you really

will not use an exposure over 1/15 if you are holding the camera. I get confused with how

Canon meters in manual mode.

 

I understand it treats the flash as a fill flash in man. mode but when I am composing a

shot the meter will say I am underexposed but I know when my flash fires the shot will

look right. How can you trust what the meter is saying if its not taking the flash into

account? anyone else have a hard time understanding this?