Help needed

Dear goodness !

I left the house this morning at 8.40 and got back in at 4.30 to find you had all been very busy on my education

OK a few comments [ if no-one minds ]

Graham - the article you pointed me to looks great , the first paragraph illustrated it nicely and then spoilt it by describing me >

I'll come back to that one later when I've hopefully started to understand depth of field a bit better - I seem to be stuck on the Goalie in the goal mouth at the moment - that I can understand

Peter - article will be read in short bits so it hopefully goes in . I love the definition of Circle of Confusion

Simonarthurs - what a great idea - I ain't got a tripod I'd trust with my K-x and I probably won't get one because of my limitations with weight . The table will be cleared and I'll see what I can do - I've an interesting little terracotta statue that I can use for the subject .

Ken - thanks for that tip I'll have a go

Chris -- I don't think he's a sweetie man - I'll try a bottle of wine - but thanks - again something that if it works for me , should help.

Martin - I'm leaving my 50-200 in the bag at present - I don't feel ready for it - though there are a couple of shots I want to get using it - but since it's still pretty cold , and cold affects my hands badly [ I lose sensation ] I don't want any accidents swapping lenses . The bigger one can wait till we have some warm days. Also sorry you've lost me totally here

Don - struggling a bit to visualise that - it makes sense - but the idiot has to work out how to set it up

With apologies for the very long post - but you have all given me such a lot of help here that it really does have to be acknowledged .

The lever in front of the shutter release button is the same, and suggests:
Pull right for DOF preview, push left to turn the camera off.
In the menu you can set two options. Using the lever to close down the aperture so you see the effect in the viewfinder or make a test image that shows on the display.(digital preview)
Perhaps an other owner can confirm this or prove me wrong, obviously.

Edit:
The Pentax website shows, I am right. See specs under viewfinder. Its found under the programmable green button. Not the lever switch, I was referring to. Sorry.

Martin it seems you're right with your edit, just had my uncles K-X in my hand and you can't pull the lever further like with the K10D.
I haven't tested the green button though
I went for diner there and just returned so didn't read your message.

Also when you look up the specs of the K-M it didn't had an optical preview so I'm glad they changed that!

@Angela what we are talking about is that you can set the camera so that when you press the green button it close down the aperture and you can see the effect of that in your viewfinder.
Since you can see how big the DOF is you can see how to place it correctly for the effect you want.

Only problem is that if you use f/22 and it's a bit dark then your viewfinder darkens almost completely.

OK - moving slightly sideways from the above - I need a bit more info.

Tomorrow as long as it's not disgusting, I intend to go and try and get my homework shot for this week It's something I got before on the P&S and is quite nice - if I manage it I should get the 'thing' in sharp focus and there is plenty of background stuff which should be nicely out of focus [ I hope ]

BUT where I will be, is near some running water which I'd also like to have a go at . If it's running fast , and I would expect it to be, I'll need to 'freeze' it - so that means a small aperture - Yes ? So how small is small ? bearing in mind I'm not totally doing this manually - he told me to use Av so I'll stick with that and it's still too cold for the 50-200m lens .

I'm not expecting these to be marvellous - but I'm using these ideas to try and get to grips with Aperture

With running water...

If you want to "freeze" it you will probably need a large aperture to give you a fast shutter speed, the down side is you get shallow depth of field.

If you want the blurry, milky effect for the water use as long an exposure as you can which will require a small aperture and, incidentally, give you a large depth of field.

Obviously, there are in-between possibilities, and you can also change the ISO but I think that is next weeks lesson!

Best wishes, Kris.

shutterspeed is how you freeze action, not aperture. Sure there is a correlation between wider apertures and faster shutterspeeds, but nonethe less it is shutterspeed that matters.

for example:
you could stop your lens right down to f32 and set your iso higher and even add light to get a fast shutter speed (flash duration being the other way to get a faster shutter speed but that is another learning curve), if your shutter is fast enough, and there is enough light for a proper exposure you can freeze action.

another example, you could have your aperture wide open at f 1.4 and still get a slow enough shutter speed to blur motion by shooting when the light levels are low or by using nd filters to cut the light.. as long as you got a proper exposure, and slower shutter speeds you get motion blur.

womble is right that there is a correlation, between aperture and shutter speeds at any given iso, but the best way to think of this is "Shutter controls motion blu/freezing, at ANY given aperture/iso setting."

Ehhhhhh......OK.
Firstly: To freeze fast moving subjects like running water, flying birds, cars etc....You must use a fast shutter speed. This usually means that the aperture is wide open or near wide open.

To use your example of running water.
Imagine the bottom of a bucket is your sensor. And the water from the tap is the light.

The diameter of the adjustable snout on the hoze is the aperture.
The crane which you use to determine the amount of water is the shutter speed.

If you open up the crane two third(1/60 sec) and set the snout at the smallest opening( F22) possible it takes say 1 minute to fill the bucket.

Now open the crane one third(1/30 sec) and set the snout at the middle opening (F.It would also take one minute to fill the bucket.

Now...returning to the camera settings. The time it takes to expose a certain scene correctly is determined by the amount of light hitting the sensor(aperture opening) and the period of time(shutter speed) the light hits the sensor.

So...to prevent a moving subject from blurring you need the shutter speed to be fast enough. But to expose correctly there must be a certain amount of light hitting the sensor. This is managed by the aperture.

Example;
To freeze the following moving subject in motion.
1# Walker in the street at normal pace: 1/30 sec.
2# Jogger running 1/100 sec
3# Bicycle driving on the road 1/250
4# driving car at 50 mph 1/500

Sorry if my example is looking a bit childish, but this is the simplest way I can explain the correlation between aperture and shutter speed.

OK - Kris = you are correct he's starting on ISO next week

Don = thanks - some of that is beyond me at present - but the basic info is going in - in conjunction with

Martin - the simple terminology that makes sense to me . I love your examples - written down for use in future - thank you

OK - so all being well tomorrow the K-x and I will go for a wee walk in the park and it will be interesting to see what I bring back from this .

Well today's walk with the K-x has been a disaster

I was told to put it in Av and shoot at an aperture of 2.8 - couldn't achieve that - nearest I could get until the very last 3 [ of 31 ! ] was 5.6. I played with the focal length a bit trying to get the subject as large as possible , but still retaining some background .

The last 3 pics I got at f4 and f3.5 - and I've done better with the Kodak C703 !!

I don't consider any of these to be keepers

It seems the "education" you're getting is not compatible with your equipment!

Your teacher should know that f2.8 is not available with the kind of zoom lenses that most of the pupils would have.

I don't think that is possible with the lens you are using (I'm presuming you're using your 18-55).

It's not too much to ask is it?

Thanks guys - you make me feel much better . He didn't actually ask us what we were using - I ~think~ from what he said he has a N...n but I could be wrong.

Until we have better [ ie warmer ] weather up here the 18-55 stays on the camera. Yes I can switch lenses , but thanks to various elbow dislocations and other fractures [ yeah - both arms ] in cold weather my sense of touch can go for a burton , so switching lenses is not a good idea except in the house , and I'm not 100% convinced that if I put the 50-200 on it would fit in my small Lowepro Bag.

Monday evening should prove interesting when I tell him I could not do as he wanted

I suspect that the teacher's thinking is rooted in the old film days when most photographers used a 50mm prime lens as a "standard" lens. These lenses have a large maximum aperture: typically f1.7 to f2.

Of course you can use a prime lens, or a fast (large aperture) zoom lens with your digital camera as well, but it's not common for beginners to have one these days.

You can get fairly close to f2.8 at the wide end of your 18-55mm (f3.5), but not at the long end where f5.6 is the maximum.

It's the long end where f2.8 would be most effective as well, in terms of producing shallow depth-of-field for dramatic effect.

The 18-55 does focus quite close, I don't know if you like to photograph flowers or small objects but you should be able to really see the transition from sharp to blur if you focus to an object nearby.