Some questions about shutter speed and F...

Discussion in 'Photography Beginners' Forum' started by flask, Jul 25, 2006.

  1. flask

    flask TPF Noob!

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    Hi guys. I just found this place and i think i've found a very good place :p
    Anyway....
    Off course you guys have more experience than me, and that's why i'm here, in order to understand what i've done wrong :(


    Anyway, this morning i took my 350D to take some pictures (i'm really a n00b! i know that, and i want to become better...)
    It was a sunny day, here at the beach, so i switched to Manual mode in order to play a little bit :p
    That's when the problem started.

    I put ISO at 100, and F to 22 (to a great image in depth of field). I don't have a tripod, so i set the shutter speed to 800 since the 18-55 lenses don't have IS...

    Result: the picture came out almost black:(


    I tried also but indoors to make a macro shot of my phone with F set to 16 and the camera 'said' that there was to much exposure. So i set the shutter speed to 30 and it went fine, but since i don't have a tripod you're guessing wich was the final result lol. A bit blured :(


    So, isn't possible to solve this problem?
    What if i wanted to shoot my phone with no flash and with a shutter of 250 at least? I can't solve this questions?


    Sorry for the bad english and for so many questions.:lovey:
     
  2. GoM

    GoM TPF Noob!

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    With the first problem, your low F stop (22) combined with your very fast shutter speed (1/800) to let in next to no light, even with the higher ISO. As you lower your F stop (to let in less light), you need to also lower your shutter speed (more towards 1/4, 1/2 sec, etc.) in order to let the 'correct' amount of light in. What I like to do is, once I find an object, take the same picture about 10-20 times, each time changing the aperture and/or shutter speed and gauging the results. If I want to just take one or two pictures at a time, then I'll keep it on automatic (or change the mode).

    So basically, whenever you decrease the f-stop, you let in less light, so to combat this you generally have to increase the shutter speed.
     
  3. flask

    flask TPF Noob!

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    This F thing is a bit confusing... by decreasing you're saying that for example the aperture go from F18 to F20?

    So there is no way to solve this problem in the camera? Only with post work?

    Ok, i was starting to think that there was a problem with the lens or the camera lol

    Sorry for so many questions lol and thank you for the fast response :)
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Welcome to the forum.

    Your camera has a built-in light meter. When you use Auto (P or [] mode) the camera sets both shutter & aperture for you...based upon the level of light coming into the lens. Same thing with Av or Tv, except that you get to choose one of the variables.

    In Manual mode, the camera's meter is still working. Do you see the scale across the bottom of the viewfinder? That is the meter scale. If you put the camera into manual mode, you should change the settings until the 'needle' is in the middle of the scale (while point the lens at your scene). You can then change the settings away from the middle of the scale...but you will be under or over exposing the scene.

    Here is a good analogy I've read. Exposure is like filling a bucket of water from a tap. You always need to fill the bucket with water...just like you have to fill the film/sensor with light. If you open the tap just a little bit...it will take longer to fill. If you open the tap a lot, it will take less time to get the same amount of light.

    If you close the aperture down to something small like F22...then it will take longer to 'fill up with light'. Same thing when you go the other way...if you open the aperture, then you will need to have the shutter be faster (less time)...otherwise it will let in too much light.

    Take your example of F22 and 1/800. You made the aperture very small and at the same time made the shutter speed very fast...basically you let very little light into the camera...and that's why it was just black. You can't just pick those settings at random. If you wanted to get lots of DOF, then you were right to use F22 but then you have to see what shutter speed the meter will give you...if it's too slow to hold without getting blurry...then you need to...a)Use a tripod or support b)Open up the aperture c)turn up the ISO.

    If you wanted to shoot your phone with a shutter speed of 1/250....set your camera to Tv mode and see what aperture the meter recommends. If it flashes...then you don't have enough light. You could pick a slower shutter speed or add light with the flash or just use any light...or move to a brighter spot.

    As for what shutter speed to use. The rule of thumb is to use a shutter speed that is faster than the focal length you are using (x 1.6 for your camera). So if you are zoomed to 50mm you will need at least a shutter speed of 1/80 (use 1/90).
     
  5. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Yes, going from F18 to F20 is decreasing the size of the aperture (bigger number = smaller aperture (hole).


    The way to solve this problem is to use the correct settings for the light you are working in. If you really want to use whatever settings you want...you will need to use your own light source...like studio lighting etc.

    The suggestion to keep trying different settings is a good one. Eventually you will figure it out. Or, don't use manual mode at first. Just use P mode or Tv or Av...look at the settings that the meter is giving you...that is what you have to work with. You can change one of the settings...but you much change (or let the camera change) the other setting to compensate. It's all about give and take.
     
  6. flask

    flask TPF Noob!

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    Oh! I'm starting to get the idea :p Tomorrow i'll try to take more shoots..

    And answer me this please. I saw the manual, and it said something about mirror blocking. It is set to disable, but i want to know if i still can shoot pictures (in manual or automatic, because the disable option can only be accessed in the creative mode, not the basic (point and shoot))with a lot of light and in some cases the sunset without damaging the CMOS sensor:confused:.
    Do i need a filter to attach in the lenses?

    Thanks a lot for the support!:D
     
  7. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Are you referring to Mirror Lock Up? That is a setting you can use that makes the mirror flip up, then the camera waits and then takes the shot. This is useful when you are shooting while on a tripod and using a remote or the self timer. Normally when you press the button, the mirror flips up out of the way (notice the viewfinder goes dark)...the movement of the mirror may cause the camera to shake...which may cause the image to be slightly blurry. So if you are on a tripod and don't want any shake at all...then use Mirror Lock Up mode.

    There are lots of things that can't be adjusted when in point & shoot mode []...or the picture modes on the dial. I have a similar camera...and I haven't used any of those modes for at least a year. Just the 'creative' modes.
     
  8. flask

    flask TPF Noob!

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    Yes, that mirror thing i understood by reading the manual, but thanks anyway :)

    Do you use any type of filter for the sun? Or i can shoot at the sun or reflections at any time? With the mirror blocking disabled off course...

    That it's my concern. This is expensive equipment.
     
  9. Digital Matt

    Digital Matt alter ego: Analog Matt

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    You won't hurt the sensor, but you might hurt your eyes by looking at the sun.

    I would suggest reading up about the basics of photography, so you can choose your settings manually with some knowledge behind it :)

    Check out this site:http://www.photo.net/learn/making-photographs/
     
  10. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Correct exposure at the beach on a sunny day at ISO 100 is around f/22 @ 1/100th (or maybe even a little slower depending on the scene). So at 1/800th of a second you were underexposing by at least 3 stops. Read up on how to use your meter in your instruction manual.
     
  11. flask

    flask TPF Noob!

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    I just found that out :p
    Thanks to all that supported me here :)

    Another question....

    I took this photo just an hour ago.

    [​IMG]

    Look at the horizon in the circles.

    Is this a problem of the camera, lenses or just a commom problem using this type of lens?
     
  12. Unimaxium

    Unimaxium TPF Noob!

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    I'm not sure I see the problem :confused:
     

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