Further advice required.

Discussion in 'Photography Forums' started by Bristol Pete, Mar 8, 2006.

  1. Bristol Pete

    Bristol Pete
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    OK, So I am learning all about aperture as we have learnt this week. So far worked out that a lower number gives a bigger depth of field and visa versa.

    However, tonight, I worked out that to get a 'still/sharp' shot indoors I needed to up my ISO to 800 or 1600 to get the shot (no tripod yet). However, Should I be looking at shutter rather then ISO here as other people have stated that they always shoot in 100 ISO and would this apply to outside too?

    As ever all advice is gratefully recieved.:smashin:

    Here are a couple of hand held shots and I think there is a notable improvement from my first depth test shots. I have also worked out that over riding and going for manual focus can help.

    Pete.
     

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  2. richard plumb

    richard plumb
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    sharp is a couple of things. Aperture and shutter speed.

    aperture is usually best at f8, so if you're aiming for a really sharp picture, try that.

    next is shutter speed. Sharp means not shaking the camera, so you need approx 1/focal length to avoid that - eg 1/50 for a 50mm lens. Bear in mind you have a 1.6x crop camera, so figure 1/100 for a 50mm lense just in case.

    so if you can get f8, 1/100 at 50mm, you should have no problems getting a sharp picture.

    Thats it.


    Oh, of course indoors where its really dark for a camera ( your eyes will have adjusted), you may not be able to get f8, 1/100. Thats where ISO comes in . Its just the sensitivity of the 'film'. Higher ISOs mean you get away with less light for the same picture.


    eg ISO 100 - f8, 1/25 (too slow!)
    ISO 200 - f8, 1/50 (getting there)
    ISO 400 - f8, 1/100 (lovely!)

    I usually find indoors even with the 50mm f1.8 that I'm bumping the ISO up. try to keep the lowest possible to get cleaner images, but the 350d will go up to 1600 pretty nicely (I'd say you could use 100-400 without a worry, but shifting up to 800, 1600 only when needed as you will get some additional noise)
     
  3. Bristol Pete

    Bristol Pete
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    Thanks Rich. I can see an improvement already from the shots of Mum the other night. Can you? I have done some with a higher F and a nice even picture so I think this is going in.....

    Looking forward to the weekend so I can get out with the camera in daylight. going to go out and shoot in aperature mode onoly and get used to that for a while and then move onto shutter etc.

    Thanks,

    Pete :)
     
  4. senu

    senu
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    Im sure there are cleverer chaps here but Ill attempt to help;)
    Sharpness depends more on lens quality, focus accuracy, smallest aperture possible for good exposure ( unless you want to be creative with DOF).
    Where ISO comes in is how it affects shutter speed and motion blur as well as digital noise. One can have sharp poorly exposed pics or well exposed blurred ones ( I know .. I have a few:rolleyes: )
    The ISO in film makes for very fine (minimal /no grain pics) at 50 / 100 etc. This however supposes the lighting conditions are optimal. The "fast" films use higher ISO and are able to capture the image with less light. In essense they are more light sensitive.but they do so at the expense of grain.

    What that implies is that if the lighting is average, A shot at iso of 100 will need to be exposed for a longer period than iso 400 to give the same level of exposure. If the object is still and a tripod is used , fine.. If not there will be motion blur on the lower iso.( because the exposure time is longer)
    In the digital realm, grain is replaced by digital noise which increases with gain. Gain is the electronic change in sensitivity to light by the ccd/ cmos sensor.
    The higher the iso, the more likely you can get a well expose image from suboptimally lit scene without motion blur because the increase in gain counteracts the need for longer exposure to light . However the elements of digital noise begin to creep in.
    For silky smooth noise-free images a lower iso is best but unless the exposure time is brief ( because lighting is ok) or object is still/ tripod is used the risk is one of motion blur.
    The 350D ( and all of canon cmos sensors) have good noise characteristics so
    going to ISO 800 ( or even 1600 in the 350D) is not a bad thing if lighting or rapid movt require it. Certainly for sports rapid movt shots where very fast shutter times are needed a higher ISO is needed to get a blur free pic
    Also, Razor sharp night shots are often made with a tripod with high iso

    So your best bet for that razor sharp picture is, good lighting, which in turn will allow low iso, as well as fast shutter speed and high f stop ( small aperture). You will definitely get this on a well lit outdoors shot
    Some of the costlier (IS) image stabilising lenses attempt to correct shake during picture taking by some complex optical means.

    Sorry to go on..:oops: .I hope some of it makes sense:boring:
     
  5. Bristol Pete

    Bristol Pete
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    Thanks so much. I must seem like a real pain but I certainly wish to use my camera in manual mode even though it is no slouch in auto mode. Desperate for the weekend to arrive so I can get out and take some pics.

    I can already see how I can improve my Bristol zoo pics with a high aperature, shutter speed etc as looking at the exif data the black and white lion was shot in F10, 1/500, ISO 250 in auto mode. When I go back which will probably be in a couple of weeks I will try other things and hopefully be able to buy my tri-pod by then. I have also worked out that I did not shoot in highest quality and I may even try RAW. Of course the brilliance of immediate results via the digital medium is superb and only last night I had to explain to Dad that I was not 'wasting film' in his words :D (Love my Dad, he is an absolute gem)

    Thanks again,

    Pete.
     
  6. Bristol Pete

    Bristol Pete
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    One final question about Fstops is that I have been unable to get lower than F4 on my camera and I pressume that this could be down to the lens or indeed light.

    Is this the case?

    Thanks.

    Pete.
     
  7. barongreenback

    barongreenback
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    Yes - your lens probably says something like f/4-5.6 this means that at its widest, f/4 is available and at the end of its range, f/5.6 is available. More expensive lenses will give you a wider aperture.
     
  8. richard plumb

    richard plumb
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    don't worry too much about fstops (IMO)

    shallow DOF is good, but you get that in spades with a DSLR. even f5.6 at a wide lens (eg 18mm) should give you pretty shallow DOF. fast lenses (wide aperture) are useful in low light - indoors - but I tend to use flash otherwise my shutter speed is too slow for kids etc.

    Separate your subject from the background slightly can help too.
     
  9. Jazz Monkey Jr

    Jazz Monkey Jr
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    A quick guide on ISO settings:

    You want the lowest ISO you can, this is usually ISO 100. This will give you the cleanest picture, as you increase the ISO you also increase the noise, but the 350D is pretty good at removing the noise automatically.
    When you have got less light you can either use a tripod to keep the ISO down or you can up the ISO to enable you to hold the camera by hand, or you can use a flash.

    Make sure that you check your ISO before taking any important pics as you may have left it set high, experiment as much as you can, it is much cheaper to learn with a digital camera as all the shots are free.
     
  10. dave_bass5

    dave_bass5
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    I would point out that a little bit of post processing adds a lot to the final image.
    It been pointed out so many times that shots from DSLR's can be a bit soft and benefit greatly from a little sharpening and if you use a high ISO then something like NeatImage or Noise Ninja can really help get rid of the noise.
    I mainly use Elements 4 (although i have PSCS2) to correct levels and shadow/highlites using lightmachine and use focalblade on the final output.

    Dave.
     
  11. Peakoverload

    Peakoverload
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    The best way to understand aperture, shutter speed and ISO is to understand that they are all relative to each other. Let me explain.

    Exposure is all about letting light a certain amount of light through the lens for a certain amount of time and allowing it to hit either a sensor or film that has a certain amount of sensitivity to light. The biggest important thing to remember is that there is no such thing as ONE correct exposure, as you will see there are various settings for exactly the same scene that will all produce a shot that is exposed correctly. What is more accurate is that there may be ONE correct Creative Exposure i.e. an exposure that gives the correct depth of field, freezes the action or allows for motion blur etc etc.

    So how do ISO, aperture and shutter speed relate to each other? Well the difference between any two settings i.e. ISO 100 and 200, 1/125th and 1/250th, f/2.8 and f/4 is ONE stop of light.

    Therefore the following exposures will all produce a shot that is correctly exposed i.e. no blown highlights or too dark,

    f/2.8 @ 1/125th ISO 100
    f/4 @ 1/250th ISO 100
    f/2.8 @ 1/60th ISO 200
    f/4 @ 1/125th ISO 200

    What this is showing is that if you increase one you must decrease one of the others. As I say each of those settings will give the same exposure so all of them are correct but probably only one of them is the correct creative exposure for you shot.

    If you are shooting hand held at 60mm you want to be using a shutter speed of at least 1/125th to avoid camera shake so you might want to use f/2.8 @ 1/125th ISO 100. However f/2.8 may be to shallow a depth of field for your shot so you drop to f/4 (or smaller) but your shutter speed will drop below 1/125th which you need to avoid camera shake so you increase your ISO to 200.

    Your camera has three main settings, forget about the creative zones for a second, Aperture Priority, Shutter Priority and Manual.

    In Aperture priority you can specify an aperture to give you the depth of field you want. The camera then chooses the shutter speed based on what's available against your ISO setting. If the camera chooses too slow a shutter speed, whack up your ISO.

    In Shutter Priority you can specidy a shutter speed to suit your focal length and or the action you are shooting. The camera then sets the aperture based on what's available at your ISO setting. If the camera chooses too small an aperture whack up your ISO, if it chooses too large an aperture decrease your ISO or choose a faster shutter speed.

    In Manual you do it all, you choose the aperture and shutter speeds from what's available at your current ISO, if you cant set a small enough aperture or fast enough shutter speed, whack up your ISO.

    Most lenses (although not all) have a minimum aperture of f/22 so this is the smallest aperture you can set, the largest aperture you can set will be marked on the front of your lens. The best lenses have a fixed aperture throughout their entire focal range and the smaller the number the better e.g f/2.8 is better than f/4. Other lenses drop one or more stops throughout their focal range and are marked, for example, f/4-5.6. So lets say you have a 70-300mm f/4-5.6 lens this means that at 70mm the maximum aperture will be f/4 but at 300mm it will only be f/5.6. Your camera wont allow you to select an aperture that is larger or smaller than what the lens will allow and it will flash if you select an aperture that wont let in enough light or too much light for lighting conditions you are in. If this happens choose another aperture, shutter speed or ISO combination.

    HTH
     
  12. Zone

    Zone
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    I think you have been given a lot of useful information to digest Pete :lesson:

    So one more won't hurt :D and is the one thing that no one seems to have mentioned!
    The Histogram, probably the most underused but most useful tool in your camera's armory, get used to looking at it after every shot.

    A simple graphical image showing where the different brightness and intensity levels are across the 5 stops of so of latitude your camera's sensor is capable of recording are, the trick being to keep the levels within this latitude without the image hitting either side, right hand=blown out whites etc.

    simple eg
    Try taking a shot and look at the histogram, if the image is too bunched either blown to the right or underexposed to the left then look at altering your settings, to darken an overexposed shot would be upping shutter speed and/or a smaller aperture or smaller iso if possible, vice verse for an underexposed shot.
     
  13. senu

    senu
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    Pete.....gosh.... bet you wish youd never asked now:rolleyes: :rotfl:
    Its all good fun , Happy snapping!;)
     

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