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Thread: A few basic but scattered questions regarding Aperture, Tv and Av modes etc.

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    A few basic but scattered questions regarding Aperture, Tv and Av modes etc.

    Apologies in advance, as I'm 100% sure the answers to these questions will be covered in other threads. I just noticed the NTP challenges in this forum, which I'm keen to try out asap. But I'm just hoping to get a few basics sorted at the moment, before the weekend. I also apologise in advance for any incorrect terminology.

    For the record, I am using a Canon 40D with a 18-200mm Canon Lens. Now:

    1. When taking landscape photos, usually in the wee hours of the morning before and up until sunrise, in the Av mode I am setting the aperture to f22 (the highest it will go). I do this to hopefully capture as much detail in every corner of the image and get what I hope is the best DOF. However, I have noticed a lot of similar (though obviously far superior) images on this forum are taken at f16.

    Can I just ask the benefit of using f16 instead of f22 in a moderately low light landscape photo? Is it that the f16 allows for a quicker shutter speed and therefore less movement? And the f22 allows for a longer shutter speed and more chance of movement?

    2. For my Canon 40D, is there a way to set the shutter speed in Av mode? Or alternatively, a way to set the aperture in Tv mode? At ISO 100 in each mode, I find it very easy to white out a photo setting a long shutter speed in Tv mode, but I can't see how to manually set the shutter speed in Av mode. I assume it's auto in this mode?

    Aside from using the Manual Mode (I assume), I was just curious to know if there is a method using Auto Focus to set both the Aperture and Shutter Speed?

    3. I have also been playing around home with the Aperture. Taking photos outside in the full sunshine of my pups and beer bottles (a new assignment I have set myself - humerous, to me at least). The problem I am constantly getting, setting a really low f number, like, for example, f4 or even f8... the images are turning out soooo dark. Even in full sunshine. I started out with the low ISO to keep the images sharp and noise free, then I went up to 400. But they kept coming out dark. Do I need to increase ISO to over 1000, but then will it bring too much noise and unsharpness to my photos? I ended up setting the ISO to Auto, but they were still coming out dark when I had it on a really low Aperture setting. Is there something really simple I'm missing?

    4. Easy one. I see a lot of you guys taking shots with super long shutter speeds... as in minutes even. The longest shutter speed I can get on my camera, that I know of, is 30 seconds. How on earth do you get a longer shutter speed than 30 seconds using the Canon 40D?

    Sorry again, guys, these are probably all really stupid questions. But any help would be most appreciated. Thanks.

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    1) you don't necessarily want every last detail highlighted. Eg. Rolling hills in the background don't need to be super sharp and may actually detract from the image.

    2) Yes, the big dial at the back (in AV mode) adjust the exposure compensation by lifting / lowering the shutter speed.

    3) What mode are you using? It would seem, your shutter speed is way too high.

    4) Remote releases often have their own timers

    Quote Originally Posted by Geoff79 View Post
    Apologies in advance, as I'm 100% sure the answers to these questions will be covered in other threads. I just noticed the NTP challenges in this forum, which I'm keen to try out asap. But I'm just hoping to get a few basics sorted at the moment, before the weekend. I also apologise in advance for any incorrect terminology.

    For the record, I am using a Canon 40D with a 18-200mm Canon Lens. Now:

    1. When taking landscape photos, usually in the wee hours of the morning before and up until sunrise, in the Av mode I am setting the aperture to f22 (the highest it will go). I do this to hopefully capture as much detail in every corner of the image and get what I hope is the best DOF. However, I have noticed a lot of similar (though obviously far superior) images on this forum are taken at f16.

    Can I just ask the benefit of using f16 instead of f22 in a moderately low light landscape photo? Is it that the f16 allows for a quicker shutter speed and therefore less movement? And the f22 allows for a longer shutter speed and more chance of movement?

    2. For my Canon 40D, is there a way to set the shutter speed in Av mode? Or alternatively, a way to set the aperture in Tv mode? At ISO 100 in each mode, I find it very easy to white out a photo setting a long shutter speed in Tv mode, but I can't see how to manually set the shutter speed in Av mode. I assume it's auto in this mode?

    Aside from using the Manual Mode (I assume), I was just curious to know if there is a method using Auto Focus to set both the Aperture and Shutter Speed?

    3. I have also been playing around home with the Aperture. Taking photos outside in the full sunshine of my pups and beer bottles (a new assignment I have set myself - humerous, to me at least). The problem I am constantly getting, setting a really low f number, like, for example, f4 or even f8... the images are turning out soooo dark. Even in full sunshine. I started out with the low ISO to keep the images sharp and noise free, then I went up to 400. But they kept coming out dark. Do I need to increase ISO to over 1000, but then will it bring too much noise and unsharpness to my photos? I ended up setting the ISO to Auto, but they were still coming out dark when I had it on a really low Aperture setting. Is there something really simple I'm missing?

    4. Easy one. I see a lot of you guys taking shots with super long shutter speeds... as in minutes even. The longest shutter speed I can get on my camera, that I know of, is 30 seconds. How on earth do you get a longer shutter speed than 30 seconds using the Canon 40D?

    Sorry again, guys, these are probably all really stupid questions. But any help would be most appreciated. Thanks.
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    Hi Geoff,

    I'll try and answer your questions

    1. f16 would give your a quicker shutter speed and possibly create less noise in the photo, I know some camera's create alot of noise the longer the shutter speed. I hope someone else can give you a more detailed explanation on this point.

    2. You cannot change your shutter speed in AV mode, the camera chooses your shutter speed based on the Aperture you want to use. And similarly you cannot choose your aperture in TV mode as they are automatic modes. edit - oops it seems you can do that, sorry I dont use AV or TV mode, I just thought they were semi-auto modes...apologies

    Not sure what you mean by using autofocus to set aperture and shutter speed? Normally when shooting landscapes in low light situations manual focus is the best choice.

    3. Do you have any examples to show us and the exif data? If its full sun, and using f4 then your shutter speed is too fast and you need to slow it down, you can do this in Manual mode by choosing your aperture, then using exposure compensation, and adjust your shutter speed accordingly so that you get correct exposure.

    4. You need to get a remote for this, set your shutter speed to bulb then expose for as long as you want.
    Last edited by triptych; 10-06-2011 at 9:12am.
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    As above, already well answered I think.

    Definitely would like to see some examples posted up of the darker photos. Lens cap is still on? All I can think of is maybe exposure compensation is right down, quite possible given that you've been playing around with the dials? On the 40D, after you've focused, and assuming you have the wheel turned on, just rotate the wheel where your thumb is clockwise/counter clockwise, and you'll see a dial in the eyepiece (or the external display) flicking around between -2, -1,0,1,2. It may be down around the -2 or -1 mark if it's coming out dark.

    I'm suspecting that these problems could be some of the reason why you're getting whited out images in Av or Tv mode as well. For a quick cheat, if you want to use full manual- go into Av or Tv mode and take note of the shutter speed and the aperture value. Then go over to manual, flick in those exact same readings, and then adjust the aperture or shutter speed according to what you want.

    I'd definitely make sure your exposure compensation was on 0 though. Rotate the big round wheel so it reads 0

    exposurecomp.jpg

    Hope that helps
    Chris
    Last edited by Bax; 10-06-2011 at 9:34am.

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    Quote Originally Posted by Scotty72 View Post
    1) you don't necessarily want every last detail highlighted. Eg. Rolling hills in the background don't need to be super sharp and may actually detract from the image.

    2) Yes, the big dial at the back (in AV mode) adjust the exposure compensation by lifting / lowering the shutter speed.

    3) What mode are you using? It would seem, your shutter speed is way too high.

    4) Remote releases often have their own timers
    Thanks Scott!

    1. Cool, so it's just a matter of personal preference? Fair enough.

    2. Haha, excellent. So basic, but I will play around with that and see if I can get some joy.

    3. Still in Av mode. Looks like I might need to apply (2) to this one. So where I've probably been going wrong is using my camera hand held in these instances, when I might need a tripod for this too?

    4. Ah, I see. I think my remote may be a bit cheap/basic for this then.

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    Quote Originally Posted by triptych View Post
    Hi Geoff,

    I'll try and answer your questions

    1. f16 would give your a quicker shutter speed and possibly create less noise in the photo, I know some camera's create alot of noise the longer the shutter speed. I hope someone else can give you a more detailed explanation on this point.

    2. You cannot change your shutter speed in AV mode, the camera chooses your shutter speed based on the Aperture you want to use. And similarly you cannot choose your aperture in TV mode as they are automatic modes. edit - oops it seems you can do that, sorry I dont use AV or TV mode, I just thought they were semi-auto modes...apologies

    Not sure what you mean by using autofocus to set aperture and shutter speed? Normally when shooting landscapes in low light situations manual focus is the best choice.

    3. Do you have any examples to show us and the exif data? If its full sun, and using f4 then your shutter speed is too fast and you need to slow it down, you can do this in Manual mode by choosing your aperture, then using exposure compensation, and adjust your shutter speed accordingly so that you get correct exposure.

    4. You need to get a remote for this, set your shutter speed to bulb then expose for as long as you want.
    Thanks for that!

    1. I'll give the f16 more of a go compared with the f22 and see how I go with noise comparison. I was liking the f22 because it gave me a little longer on the shutter speed too, when I was after water movement, so I'll have to factor that in too.

    2. Hmmm, that's what I thought too. I'll play around with what Scott said and confirm this this afternoon.

    3. No examples here at work today, but I'll have some at home. It sounds like I do need to slow down the shutter speed. I was just looking for quick fixes on these types of photos to be honest, without a tripod set up etc. Maybe I'm just being too lazy about it. I really need to try the Manual mode sometime, just to see how I go.

    4. Again, definitely sounds like I have a very cheap remote. Not that I'm knocking it, it's been a great friend of mine and a loyal servant for a very long time. But I might have a sneaky look on ebay today for a more advanced one.

    Thanks again for your help.

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    Goeff, any remote will do the trick for longer than 30 seconds.

    However you will have to be in manual mode. If you keep flicking the wheel back you will hit 30", then one more back and you hit b. Which is bulb mode and it will allow you to leave the shutter open for as long as you want to stand there holding the button.

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    Arch-Σigmoid Ausphotography Regular ameerat42's Avatar
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    Look up the term "diffraction". It can affect image quality as well.
    Am.
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    Quote Originally Posted by Bax View Post
    As above, already well answered I think.

    Definitely would like to see some examples posted up of the darker photos. Lens cap is still on? All I can think of is maybe exposure compensation is right down, quite possible given that you've been playing around with the dials? On the 40D, after you've focused, and assuming you have the wheel turned on, just rotate the wheel where your thumb is clockwise/counter clockwise, and you'll see a dial in the eyepiece (or the external display) flicking around between -2, -1,0,1,2. It may be down around the -2 or -1 mark if it's coming out dark.

    I'm suspecting that these problems could be some of the reason why you're getting whited out images in Av or Tv mode as well. For a quick cheat, if you want to use full manual- go into Av or Tv mode and take note of the shutter speed and the aperture value. Then go over to manual, flick in those exact same readings, and then adjust the aperture or shutter speed according to what you want.

    I'd definitely make sure your exposure compensation was on 0 though. Rotate the big round wheel so it reads 0

    exposurecomp.jpg

    Hope that helps
    Chris
    Thanks Chris. I did let out a laugh at the lens cap comment. When it comes to me and photography, sadly it's not out of the question.

    Anyway, thanks for the other info too. Sounds like I have some playing around to do.

    Oh, and one other quick thing. I can't post photos of beer bottles with labels on them here, can I? I might not even be able to show these shots for you guys' inspection.

    For all those thinking 'What on earth is this tool doing taking photos of beer bottles?' allow me to quickly explain:

    Whenever my wife and I go on holidays overseas, I (obviously to most, I hope) drink nothing but the local/native beers in our holiday destination. For memory's sake, I always decide to take a photo of the beer bottle too. Preferrably in a typical holiday setting. I have some fun shots of Fiji Premium on the golden shores at low tide, Vanuatu Bitter on reef on an outgoing tide, Vailima doing something silly in Samoa, three different local beers lined up in a row on our balcony in the Cook Islands with the ocean as a backdrop (*drools*) - that was a good shot... but yeah, though the years I've gathered quite a collection.

    At home, though, my friends and family know me as the chameleon of beer drinking. Every time they see me I have a new case of a different beer that I've picked up for a sweet price. I must have drunk hundreds of different beers in recent years, and I've decided now that it doesn't only have to be on holiday that I document all the different types - why can't I do it at home too?

    So starting last weekend I decided to snap at least one shot of every single different beer I consume, and I'll see if I can get a whole album's worth. My mate collects the actual bottles and cans of all the different beer he's had - me, I'm thinking of the more space concious method. I already have my walls lined with about 8 million CDs. Plus, it keeps it interesting because I don't want the same shot twice.

    So if you're out taking photos at the beach and you see some idiot lying on the sand with incoming waves approaching a beer bottle in the shallows... well, it's probably me.

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    Quote Originally Posted by Bax View Post
    Goeff, any remote will do the trick for longer than 30 seconds.

    However you will have to be in manual mode. If you keep flicking the wheel back you will hit 30", then one more back and you hit b. Which is bulb mode and it will allow you to leave the shutter open for as long as you want to stand there holding the button.
    Oh, okay. I get it. So you don't actually set anything for 3 minutes, for example? You just hold the button down for 3 minutes in this bulb mode? That explains it! Thanks!

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    Geoff in Manual Mode the exposure compensation is cancelled , Like Bax said, If using AV or Tv make sure the scale is on Zero, BTW , With the 10-20 Sigma, I hardly ever go over f10 for my seascapes, Mostly f8, Most lenes have a sweet spot around that Area, Geoff, Just try manual mode , Set ISO 100, Pattern metering, On the back big wheel set your aperture to whatever, Then using the top dial near the shutter button start dialing in the Shutter speed till you get the right exposure by checking the shot on the lcd screen , Dont touch anything else just keep on adjusting the shutter speed and checking , Thats an easy way
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    Quote Originally Posted by Geoff79 View Post
    Oh, okay. I get it. So you don't actually set anything for 3 minutes, for example? You just hold the button down for 3 minutes in this bulb mode? That explains it! Thanks!
    That's the one, and you can buy remotes off eBay that allow you to set the timer. For example if you really wanted to, you could have it setup to take X shots, for X minutes duration each, X minutes apart.

    As for the photos of the beer bottles, I'm sure we've all done it before!! But I did it purely because it was there and it was still, at least your reason has a bit more purpose than mine.

    Anyway, best of luck, keep us updated and post up some pics. I don't think it's a problem having any beer logos or anything here.

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    Quote Originally Posted by Bax View Post
    That's the one, and you can buy remotes off eBay that allow you to set the timer. For example if you really wanted to, you could have it setup to take X shots, for X minutes duration each, X minutes apart.

    As for the photos of the beer bottles, I'm sure we've all done it before!! But I did it purely because it was there and it was still, at least your reason has a bit more purpose than mine.

    Anyway, best of luck, keep us updated and post up some pics. I don't think it's a problem having any beer logos or anything here.
    Excellent, thanks!

    If it's okay to post these silly beer shots, maybe I'll start a thread or something, when I get the photos sorted. In a moment of pure luck and glee, I kicked a long-dead old external hard drive back to life just last night and got ALL my photos from it before it dies again. I was actually really concerned about photos I'd have lost if I never got it working again, but now I'm back in action.

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    Geoff, another member mentioned looking up the term 'diffraction'. This was an attempt to explain why a lot of photographers would choose an aperture of f/16, rather than f/22 to get optimal sharpness for a landscape image. When you use a really small aperture, you start getting diffraction occurring. Someone correct me if I'm wrong, but I believe this is where light is bent when passing through a small opening. What this means for your images is that rather than being nice and sharp, you'll end up with fuzziness all over the frame.

    You may want to check this page out here - http://www.secondpicture.com/blog/di...apertures.html

    It has some really good examples showing the fuzziness from diffraction, compared to using some larger apertures.

    After searching a little, I found one person suggesting that diffraction starts occurring with your 18-200 lens at around f/8. Which means if you stop down to f/11 or further, you will actually end up with images that are less sharp than at f/8. Diffraction gets worse as you stop down further, so the diffraction occurring at f/11 won't be as bad as the diffraction occurring at f/22. So it can be a bit of a compromise between how much depth of field you want, and how much diffraction you're prepared to live with.

    I know you didn't ask about this, but judging by your questions it may be of interest to you. If you want to maximize the amount of in focus area within your photos, something you'll be interested in calculating is 'hyper focal distance'. You can calculate it on the net here - http://www.dofmaster.com/dofjs.html
    Just put in the details of your camera, and what focal length you're going to use (ie 18mm) and what aperture you're going to use (ie f/11 or f/16). Subject distance doesn't really matter at this point, but change the feet to meters if you're more comfortable with those measurements. Then press calculate. You will see Hyperfocal distance listed on the right hand column, near the bottom. With 18mm at f/11, on a canon 40D, this distance is 1.53m. So when you go out next time, try setting your camera with those settings, focus on something that is about 1.5m away (keeping in mind you'd rather over estimate and focus on something that's further than 1.5 than something that's closer.)

    Find the hyperfocal distances for 18mm at f/8, f/11, and f/16, then try using them out in the field, each time focusing at the corresponding hyperfocal distance. You might be surprised by your results as to which aperture settings produce the sharpest images. Another listing in that depth of field calculator is the near focus limit. I checked how that changes between f/8, f/11, and f/16, you only gain an extra 40cm each time you make the aperture smaller. Considering the near focus limit at f/8 is 1.76m, you don't actually gain any extra benefit by making your aperture smaller, unless you have something you want in focus closer than 1.76m...

    Phew - that turned out a bit longer than I expected... hope it's helpful - if anything's not clear, feel free to ask

    Luke

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    Quote Originally Posted by Lucas View Post
    After searching a little, I found one person suggesting that diffraction starts occurring with your 18-200 lens at around f/8. Which means if you stop down to f/11 or further, you will actually end up with images that are less sharp than at f/8. Diffraction gets worse as you stop down further, so the diffraction occurring at f/11 won't be as bad as the diffraction occurring at f/22. So it can be a bit of a compromise between how much depth of field you want, and how much diffraction you're prepared to live with.
    Luke
    Hmm, Luke. That's comprehensive, and the reference to diffraction was a good one. The excerpt above needs just a bit of combing...
    An 18-200mm zoom lens represents a great range of focal length and hence a corresponding range in the effects of diffraction. You cannot imply that the effects will be the same throughtout the range. This is what the above quote seems to hint at.

    The aperture represented by f/22 is going to be about 11 times wider at f=200mm than the same aperture at f=18mm.

    Am.

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    Quote Originally Posted by Lucas View Post
    Geoff, another member mentioned looking up the term 'diffraction'. This was an attempt to explain why a lot of photographers would choose an aperture of f/16, rather than f/22 to get optimal sharpness for a landscape image. When you use a really small aperture, you start getting diffraction occurring. Someone correct me if I'm wrong, but I believe this is where light is bent when passing through a small opening. What this means for your images is that rather than being nice and sharp, you'll end up with fuzziness all over the frame.

    You may want to check this page out here - http://www.secondpicture.com/blog/di...apertures.html

    It has some really good examples showing the fuzziness from diffraction, compared to using some larger apertures.

    After searching a little, I found one person suggesting that diffraction starts occurring with your 18-200 lens at around f/8. Which means if you stop down to f/11 or further, you will actually end up with images that are less sharp than at f/8. Diffraction gets worse as you stop down further, so the diffraction occurring at f/11 won't be as bad as the diffraction occurring at f/22. So it can be a bit of a compromise between how much depth of field you want, and how much diffraction you're prepared to live with.

    I know you didn't ask about this, but judging by your questions it may be of interest to you. If you want to maximize the amount of in focus area within your photos, something you'll be interested in calculating is 'hyper focal distance'. You can calculate it on the net here - http://www.dofmaster.com/dofjs.html
    Just put in the details of your camera, and what focal length you're going to use (ie 18mm) and what aperture you're going to use (ie f/11 or f/16). Subject distance doesn't really matter at this point, but change the feet to meters if you're more comfortable with those measurements. Then press calculate. You will see Hyperfocal distance listed on the right hand column, near the bottom. With 18mm at f/11, on a canon 40D, this distance is 1.53m. So when you go out next time, try setting your camera with those settings, focus on something that is about 1.5m away (keeping in mind you'd rather over estimate and focus on something that's further than 1.5 than something that's closer.)

    Find the hyperfocal distances for 18mm at f/8, f/11, and f/16, then try using them out in the field, each time focusing at the corresponding hyperfocal distance. You might be surprised by your results as to which aperture settings produce the sharpest images. Another listing in that depth of field calculator is the near focus limit. I checked how that changes between f/8, f/11, and f/16, you only gain an extra 40cm each time you make the aperture smaller. Considering the near focus limit at f/8 is 1.76m, you don't actually gain any extra benefit by making your aperture smaller, unless you have something you want in focus closer than 1.76m...

    Phew - that turned out a bit longer than I expected... hope it's helpful - if anything's not clear, feel free to ask

    Luke
    Holy wowser, Luke. Thanks a million for that. I did see the diffraction post and had a quick look but I was a little bamboozled. Your post has made it super clear, and you've certainly made me re-think my f22 attempts. As I've said several times in my photo threads, and other people have commented, I do still get a bit of fuzziness and images not as sharp as I know they could be. But this helps a lot. I'll investigate the 2nd part of your message in detail too - thanks a heap!

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    Hi Geoff,

    I would recommend you read the book "Understanding Exposure" by Bryan Peterson. You wont regret it and you will learn so much from it, and after reading it you will be confident in using your camera on Manual.

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    Quote Originally Posted by ameerat42 View Post
    Hmm, Luke. That's comprehensive, and the reference to diffraction was a good one. The excerpt above needs just a bit of combing...
    An 18-200mm zoom lens represents a great range of focal length and hence a corresponding range in the effects of diffraction. You cannot imply that the effects will be the same throughtout the range. This is what the above quote seems to hint at.

    The aperture represented by f/22 is going to be about 11 times wider at f=200mm than the same aperture at f=18mm.

    Am.
    Hmm, very interesting, I hadn't considered that before - something I'm going to have to investigate further. Thanks for the heads up!

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    Member harmo's Avatar
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    Hi there,
    It's true that higher F stop values will increase depth of field, and I agree with the responses above where detail may not always be a benefit to your shot. But it's a fact that lenses have a "sweet spot" where everything sharpens up (stopped down from wide open) somewhere usually between f8 and f11. I've had some pretty decent landscape shots done as low as f11 (that was a surprise, I can tell you). While that's usually a bit low for most landscape work, it's important to figure out how best to use each of your lenses. Take the same shot multiple times while trying a few values ranging from f8 to f22 and see how you go, you might be very surprised at what works for you!

    I hope this helps!
    Harmo

  20. #20
    It's all about the Light!
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    its really complicated when you consider the limit of diffraction.
    http://www.cambridgeincolour.com/tut...hotography.htm

    Simply... a lower f/stop is sharper, so maybe at shorter focal lengths and apertures at f/11 or f/16 you can get a better result.

    On the other hand, night shots you may want the star effect of diffraction.

    You have a bunch of creative choices here.

    Generally for landscape, esp. in low light, use a tripod!
    Last edited by Kym; 10-06-2011 at 7:02pm. Reason: spelling
    regards, Kym Gallery Honest & Direct Constructive Critique Appreciated! ©
    Digital & film, Bits of glass covering 10mm to 500mm, and other stuff



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