DPChallenge: A Digital Photography Contest You are not logged in. (log in or register) 
 

DPChallenge Forums >> Tips, Tricks, and Q&A >> f/stops & shutter speed - help please!
Pages:  
Showing posts 26 - 38 of 38, (reverse)
AuthorThread
 01/24/2005 12:56:25 PM · #26
i'm not sure how your camera/lens works - but it is possible all of your aperture settings are not availble at all zoom settings. sometimes with a long zoom - the aperture can't open as much. f:2 might not be available until you zoom out some. if that is the case you would have to use a one stop slower shutter speed instead to compensate ( to let the same amount of light in as f:2 would ).


01/24/2005 01:09:01 PM · #27
Originally posted by dsb_mac:


As an anology imagine yourself eating yummy whip cream from a big hose. So you open wide and eat whip cream til you pass out. Then you wake up feeling hungry again and go for more. This time you make a small hole with your mouth. What happens now? You have to keep your mouth open longer till you pass out because your mouth is smaller. Each time you get the same amount of cream but notice the different ways you can do it. This is the same with exposure.



I must say, I'm amazed. Does anyone know where to get a whip cream hose?
 01/24/2005 01:24:36 PM · #28
Originally posted by SummerBreeze:
Thanks everyone for your helpful information - I get it now...I think since we had to rush through everything it was really hard to know exactly what to do.

Here is a question maybe someone can answer, when I'm out there taking pictures - sometimes the camera will not let me stop down a full stop. Like, let's say I take the picture at f/4 (because that's the recommended setting) & then when I try to stop down & go to f/2 it won't let me go down to that (even though it's in manual mode). Any ideas why that happens?

The c4000 only offers f2.8-f11 apeture settings. (Which actually is pretty good for a non-slr) How have you gotten it to recommend a setting in Manual ? Or are you following the + - setting in the corner ?
 01/24/2005 02:10:18 PM · #29
Originally posted by SummerBreeze:
Here is a question maybe someone can answer, when I'm out there taking pictures - sometimes the camera will not let me stop down a full stop. Like, let's say I take the picture at f/4 (because that's the recommended setting) & then when I try to stop down & go to f/2 it won't let me go down to that (even though it's in manual mode). Any ideas why that happens?


Lets complicate this a little further. f/2 is not the next stop from up (as in open up) from f/4. f/2.8 is.

This is your scale of full stops.

1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 44, 64

The lower the number the more the light is alowed into the camera. Thus to go from say f/8 to f/5.6 is to open up one stop.

As far as you not being able to reach f/2 that is probably because that aperature setting is not on the particular lens you are using. Not all lenses have the full range of f/stops. For instance very few lenses for 35mm cameras will stop all the way down to f/64. Many won't go past f/22.

And only a fast lens will stop down below f/2.8. (even f/2.8 to f/8 can be condsidered extremely fast as you get farther up in the telephoto range)

Some (very expensive) lenses will open all the way to f/1. That type of lens is not one you are using in your photo class.

I hope this helps.

Message edited by author 2005-01-24 14:29:47.
 01/24/2005 02:23:53 PM · #30
I must say, I'm amazed. Does anyone know where to get a whip cream hose?

LOL

I always use the example of a water faucet. You can open up the faucet a little and take a minute to fill a glass, or open it up all the way and take a second to fill the same glass. The amount you open the faucet is the aperature, and the time you have the faucet open is the shutter speed. Either way, you fill the glass (proper exposure).
 01/24/2005 02:30:53 PM · #31
Summerbreeze,

It sounds like you got TONS of info and may have a handle on it now but here is the way I learned it...think of the f-stops as the iris of your eye, when you are in a dark room it opens more to allow more light in, when you are in the sun it closes down to allow less light in. As far as the shutter speed goes, the more open your iris/shutter the more light comes in so it doesn't have to be open as long to get what it needs. It also helped me to open the camera (without film of course) and look in the back at the shutter as you adjust the f-stop and shutter speed, you will actually see how long it's open and how much when you take the picture.

Good luck on your courses

Message edited by author 2005-01-24 14:31:22.
 01/24/2005 03:14:21 PM · #32
nsbca7-
Ok, you are saying that every time you move up and down on this scale:
1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 44, 64

- then you are moving 1 full stop. So, from going from f/4 to f/2.8 you are increasing 1 full stop. And from going from f/4 to f/5.6 you are decreasing 1 full stop.

See, this is why this is so confusing. My instructor says when you select the next number you are only moving a half stop, so you have to double it....so the way he describes if if you start at f/4 you would actually go to f/8 for one complete stop down (in this case 5.6 would only be a half stop). I know I didn't misunderstand him because I emailed him to see if I was doing the assignment right. I gave him my first three shots as an example of what I have been doing. He said I am doing half stops, not 1 full f/stop.

This is why I am confused, you select the next number & say it's a full stop (just as I did) - but he says you have to double it. So in other words, I have broken the scale down to whole & half stops numbers:

1, 2, 4, 8, 16, 32, 64

1.4, 2.8, 5.6, 11, 22, 44,

So, if I get an initial f/stop from the first line, then I move backwards or forward to complete a full stop. And if I get an initial reading from the second line, I move backwards or forward to get a full f/stop. So:

F/4
+1 = f/2
-1 = f/8

F/5.6
+1 = f/2.8
-1 = f/11

Is this correct for a FULL F/stop?

As far as not being able to go below f/4 in some instances, perhaps it is the lens. It is a 28-80mm.

Ironworker-
I'm not using my digital for the photography class, the class is for film photography. I'm using a Cannon EOS 650.

**I apologize if I gave anyone a headache in this thread, there just seems to be conflicting information & it's hard to know what to follow**
 01/24/2005 03:21:19 PM · #33
SummerBreeze,

nsbca7 is right about the scale. On most SLR cameras there are additional stops (1/2 or 1/3 stops depending on the camera).

To see this, set your camera to either aperture priority or manual and change the aperture while keeping the shutter button half depressed. Watch what numbers show.

The following page gives a good description of f-stops and shutter speed.

//www.luminous-landscape.com/tutorials/zone_system.shtml

Message edited by author 2005-01-24 15:37:41.
 01/24/2005 03:46:48 PM · #34
Originally posted by SummerBreeze:
nsbca7-
Ok, you are saying that every time you move up and down on this scale:
1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 44, 64

- then you are moving 1 full stop. So, from going from f/4 to f/2.8 you are increasing 1 full stop. And from going from f/4 to f/5.6 you are decreasing 1 full stop.

See, this is why this is so confusing. My instructor says when you select the next number you are only moving a half stop, so you have to double it....so the way he describes if if you start at f/4 you would actually go to f/8 for one complete stop down (in this case 5.6 would only be a half stop). I know I didn't misunderstand him because I emailed him to see if I was doing the assignment right. I gave him my first three shots as an example of what I have been doing. He said I am doing half stops, not 1 full f/stop.



If that is indeed what your instructor said, then he is wrong! The values that nsbca7 gave are correct for full stop changes. That should be well known by your instructor, and I suspect that you have misunderstood.
 01/24/2005 03:57:25 PM · #35
Originally posted by SummerBreeze:
nsbca7-
Ok, you are saying that every time you move up and down on this scale:
1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 44, 64

- then you are moving 1 full stop. So, from going from f/4 to f/2.8 you are increasing 1 full stop. And from going from f/4 to f/5.6 you are decreasing 1 full stop.



Correct. You never stated, or I somehow missed what camera you are using, but most older manual focus lenses have half stop increments that are not marked in numbers on the ring but are there in clicks and that is what your teacher is talking about. f/9.5 would be a half stop between f/8 and f/11.
 01/24/2005 04:02:43 PM · #36
Originally posted by SummerBreeze:
Thanks everyone for your helpful information - I get it now...I think since we had to rush through everything it was really hard to know exactly what to do.

Here is a question maybe someone can answer, when I'm out there taking pictures - sometimes the camera will not let me stop down a full stop. Like, let's say I take the picture at f/4 (because that's the recommended setting) & then when I try to stop down & go to f/2 it won't let me go down to that (even though it's in manual mode). Any ideas why that happens?


Same thing happens to me!
 01/24/2005 04:09:56 PM · #37
Ignore this if it is confusing, but sometimes extra detail helps things click...

It's easy to understand how leaving the shutter open for twice as long will let twice as much light hit the film. That's why the sequence of shutter speeds doubles: 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/125, 1/250. To make things a little easier to remember, they are rounded so you have 1/30 and 1/60 instead of 1/32 and 1/64. The difference is very small, so can be ignored.

The f-stop is different. A setting of f/x means that the opening is the focal length of the lens (f) divided by x. So if you have a 50mm lens at f/2, the opening has a diameter of 50/2 or 25mm. But that's the diameter; the amount of light the lens lets through depends on the area of the opening, which is proportional to the square of the diameter. So to double the amount of light that reaches the film, you need to increase the opening not by 2, but by the square root of 2 (1.414...). If you double the diameter (or half the f/number), say from f/8 to f/4, you quadruple the amount of light that gets through, which is two stops.

So to decrease the aperture by one stop, you multiply it by 1.4, or just use the next number in the sequence 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 44, 64, etc. To decrease the aperture by two stops, you multiply it by 2, or skip a number in the same sequence.
 01/24/2005 05:10:10 PM · #38
Originally posted by thewriterside:

I must say, I'm amazed. Does anyone know where to get a whip cream hose?


I always keep one handy in my camera bag!
Pages:  
Current Server Time: 08/03/2025 07:13:32 PM

Please log in or register to post to the forums.


Home - Challenges - Community - League - Photos - Cameras - Lenses - Learn - Help - Terms of Use - Privacy - Top ^
DPChallenge, and website content and design, Copyright © 2001-2025 Challenging Technologies, LLC.
All digital photo copyrights belong to the photographers and may not be used without permission.
Current Server Time: 08/03/2025 07:13:32 PM EDT.