Aperature/Shutter Speed

[shingfan]

Weaving Wax....one thing at a time.

if original is f/16, ISO 100, 1/250
then you moved f/16 -> f/11..this is moving one stop bigger in aperature....thus allowing more light to enter.....so adjust to the same exposure....you would either need to reduce the ISO or shutter by one stop....so you would use either ISO 50, 1/250.....or ISO 100, 1/500

 

[Weaving Wax]

OH!!! So, either way you go. It's the same exposure. It doesn't matter if I move the ISO or Shutter Speed. Thanks..

 

[Weaving Wax]

Ok, I really want to understad this. I've read books and stuff, but it's still difficult for me to grasp.

Ok...

I can move either the shutter speed OR the ISO the same amount of times I move the Aperture, BUT in the opposite direction, correct? I don't move both?

Ok...some questions to make sure I got it..

1. You can only change the ISO on the fly with digital, so...for film would I just move the shutter if I only work in 400 ISO?

2. Do I always start with f.16 and work my way from there or can I start from anywhere?

Sorry I just really want to get this...

 

[shingfan]

for me....depends on what i'm shooting.....most of the time i would start with shutter speed......and then determine what aperature is required.......unless i'm interested in playing with DOF>..then i would start with aperature and then adjust shutter....but this is only good for still life when shutter speed is less significant or with the aid of a tripod when the shutter become too slow........at the end.....this is the formula that you use

exposure = ISO * shutter / aperature ^ 2

 

[Weaving Wax]

So, ISO times shutter divided by aperature to the 2nd power, or times 2?

It's hard for me to determine what aperature is required if I can't make the connection between the 2.

I don't really get the formula...

 

[shingfan]

So, ISO times shutter divided by aperature to the 2nd power, or times 2?

It's hard for me to determine what aperature is required if I can't make the connection between the 2.

I don't really get the formula...

ISO (times) shutter (divided) by aperature square

let me give you an example

say this would be an ideal setting to obtain a proper exposure in a given situation

ISO: 100
shutter: 1/100
aperature: 2

exposure = ISO * shutter / aperature^2 = 100 * 1/100 / (2)^2 = 0.25

to achieve exposure value of 0.25...you have many options

ISO: 200, shutter 1/200, aperature: 2
or
ISO: 400, shutter 1/400, aperature: 2
or
ISO: 100, shutter 1/200, aperature: 1.4
or
ISO: 200, shutter 1/100, aperature: 2.8

you have many many coptions....at the end you want to obtain 0.25 as exposure

but of course....you cant carry a calculator with you all the time when shooting picture....so what most ppl do is...they know what setting woudl provide a good exposure at a certain situation....then if they need to change shutter....they would not touch the ISO...but adjust the aperature to acheive the same exposure.......unless they are already at hte largest aperature...then they would need to adjust the ISO to compensate for the remaining factor....is this more clear?

 

[Weaving Wax]

Ok...so...that will come up with one number, correct? I don't do well with math, never did. Didn't get a proper High School Diploma because of it. So, I'm still clueless with the formula.. I have no idea how to get the right numbers to plug into the formula. And what do I do with 1 number?

I'd just like to understand the chart and work it that way.. I work better if there's a visual.

 

[shingfan]

Ok...so...that will come up with one number, correct? I don't do well with math, never did. Didn't get a proper High School Diploma because of it. So, I'm still clueless with the formula.. I have no idea how to get the right numbers to plug into the formula. And what do I do with 1 number?

I'd just like to understand the chart and work it that way.. I work better if there's a visual.

if you are not good with numbers and think that formula is too hard....i think getting a light meter would be a good idea...or dont use full manual.......not necessary to use full manual unless you are doing something creative with the exposure

the chart is basically a table of all combination that would yeild the same exposure value.......after you finish the chart and understand it....hopefully you'll understand how the formula works

let me try to use a real life example...

you have coins in your pocket....nickel, quarter, and penny

if i ask you to give me 50 cents.....what would you give me?...you can give me 2 quarters.....50 pennies....10 nickels....or combintion of the three kinds.....but you try to sum up to 50 cents right?....is the same idea with exposure....you play with ISO, aperature, and shutter to come up with the ideal exposure all the time...except the exposure formula works a little differently.....

try to understand it like this.......if you add/remove either ISO/aperature/shutter.....then you would want to remove/add the same amount from other variants.......ISO and shutter weight the same with the except of the aperature weighting double....

 

[bikeuphill9]

Shingfan : What does the exposure number mean? I understand the formula, but have no idea how to apply the number I get to the different light conditions that I am shooting. Thanks.

 

[shingfan]

Shingfan : What does the exposure number mean? I understand the formula, but have no idea how to apply the number I get to the different light conditions that I am shooting. Thanks.

you would need different exposure value for different amount of available light....imagine you are shooting outdoor with plenty of natural light....you would only need a small amount of exposure.....on the other hand....if you are shooting indoor with limited light....you would need larger exposure.....as to what exposure value you need.....the best way to find out way be by trial and error....or again...use light meter to determine.......you wouldnt expect anyone to know what exposure value to use right off their head by looking at the light.....

you dont necessarily need to know what exposure value to use for different light condition....what you need to know is how to adjust ISO, aperature, shutter speed to achieve the same exposure under the same condition........play aroud with different setting to get more familiar with what setting to use

 

[GilTphoto]

I just explaining aperature usage in another thread:

http://www.thephotoforum.com/forum/showpost.php?p=655473&postcount=11

 

[Weaving Wax]

Thanks guys!! I like your post, GilT. I'll do some more experimenting and try to figure it out. Thanks for explaining things as well, shingfan.

 

[RacePhoto]

Thanks guys!! I like your post, GilT. I'll do some more experimenting and try to figure it out. Thanks for explaining things as well, shingfan.

If I had started out taking pictures, and had to worry about all the wheels, dials, ISO, EI, histograms, editing software and what not, I may have gone crazy. With that in mind...

Film, you put it in the camera, make sure the meter knows what speed the film is, and there you very well are, because it's not going to change for 24-36 pictures. Your ASA was set. So now it's ISO. Unless the situation changes, you could probably start with one ISO and not change it, unless you move from outdoors to indoors, the light changes or you go from shooting flowers to racing cars!

Point being, you can concentrate on two variables, instead of trying to juggle three. While they are related, the ISO is less of a matter of individual exposure and more concerned with the range you will have for all your exposures. Meanwhile shutter speeds and f-stops often change with every picture.

B&W film has more latitude than digital. Film cameras have far less control when taking pictures. I think that's good for learning, because you can build a good foundation on the core skills without electronic rescue from photoshop or some other editing software. Also without needing to carry a book to understand the menues and settings on the camera.

 

[xfloggingkylex]

I like shooting in aperture priority simply because its quicker (only adjust one thing) and if a snap a shot and it looks improperly exposed, my exposure compensation can adjust that with the spin of a dial.

As for ISO, I leave it on my lowest all the time and only up it if I cant reach the exposure I want with the equipment I have (no tripod for example).

 

[markc]

I can move either the shutter speed OR the ISO the same amount of times I move the Aperture, BUT in the opposite direction, correct? I don't move both?

One or both, as long as it adds up to the same number of spaces the first one moved. Basically all the moves have to add up to zero, however you do it.
+1/-1
-1/+1
+2/-2
-2/+1/+1
+3/-1/-2
-2/+4/-2

1. You can only change the ISO on the fly with digital, so...for film would I just move the shutter if I only work in 400 ISO?

ISO would be locked unless you change the roll, so yeah, you'd only be changing the shutter and aperture.

2. Do I always start with f.16 and work my way from there or can I start from anywhere?

That's just if you are using the sunny 16 rule, don't have a meter, and it's sunny out. If you have a light meter, which most modern cameras have built in, you start with whatever readings you get. And you can change any one of them first. In practice you don't have to know this since the camera usually takes care of it, but it's good to know what's going on, and why you can't take a narrow aperture shot with low ISO and fast shutter speed when there isn't much light. You can't move them all in the same direction. Something has to give.