A rant on aperture

[imhotep]

The point I'm at with my photography is something like this - the only thing that seems to be consistent between all of my shooting sessions is that a small fraction of my photos are actually representative of the vision that I had for them.

Most of the time, the problem seems to center on my lack of mastery with setting my aperture. The kind of dissappoints I'm talking about are, for example, a background that is out of focus when I wanted it to be as sharp as the foreground. Sometimes it could be just the opposite - an entire table of decorations at a wedding is in focus, and all I wanted was for the rose closest to my lens to be sharp with the rest blurred.

I'm having these problems despite my best efforts to learn about how to use and choose my camera settings appropriately. My head is literally spinning from all of threads I've read on choosing the right aperture, ISO, and flash settings for a given situation. There's so much information and so many things to learn that I'm feeling overwhelmed trying to apply it all.

Should I just set my camera to P and my lens to AF and get over it? I don't want to do that. That's how I started out a few years ago, and those were the days of getting zero photographs that matched my vision. These days at least I get a few here and there :)

[cdifoto]

Just remember small f number = narrow depth of field and large f number = deep depth of field. If you want to blur the background, open up your lens. If you want everything in focus, stop it down. Short of having a DOF calculator with you at all times, choosing the right aperture for the right DOF is more guesstimation than anything. It comes easier with practice.

[Billginthekeys]

it sounds like you need to learn a bit about depth of field, and the way that your focal legth, aperture, and distance effect it. Depth of field is the effect that allowes a certain amount of a picture to be in focus, and certain parts out of focus. I will start by giving some general rules. in general. the smaller Fstop number you are using, the wider open the aperture, and the thinner of a depth of field that will be achieved (aka, low fstop= less in focus). Another rule is that the longer mm the lens, less will be in focus. Hence a telephoto will allow more background blur of a subject than a wide angle. Also, the distance between your subjects has a lot to do with this. first of all, for good subject isolation (aka thin depth of field) you will want to be as close to the subject as you can in the foreground (whats in the front of the image), and you will want the background as far away as possible. this creates a large difference in the background blur, because a much higher Fstop would be required in order to get the background to be in focus. and there comes in the opposite meathod. if you want two things to be both IN focus. you need to get them as close together (in distance from the lens, not parrellel to eachother) and if possible use a higher fstop in order to widen your depth of field and get as much of the frame in possible. and on your camera there is an easy way to see how much depth of field you have. it is the depth of field preview button, located on the front of the camera body under the lens release. simply press it down, and it will close the lens diaphram down to the aperture you have selected, and show you what is going to be in focus. once you are happy, set the shutter speed to match (if it is too slow you may need a tripod) and shoot the picture (mind you you have to release the depth of field button before you do this).

So that would be my depth of field basics guide. now get out there and experiment with that and see what you come up with.

[Woolburr]

Once again...give "Understanding Exposure" by Bryan Peterson a read. Great way to clear up those lingering questions. Remember that f/1 is a very narrow depth of field...just like the number 1 is very narrow.....f/22 is a wide depth of field...just like the number 22 is wider than the number 1.

[tlc]

a very good way to learn is to take a chart - mark your aperture down each time and each time taking it either down or up a notch - taking a picture with each change of course.

view your photos and match them up according to the chart and see the difference - also, its best if you take a pic of the same thing. that's how we learned in class, you can read read read until your blue in the face, but seeing it happen in front of your eyes somehow stays with you.

:p

[Jason77]

have you tried using the DOF preview button on the camera? i've been finding that to be pretty useful.

[In2Photos]

have you tried using the DOF preview button on the camera? i've been finding that to be pretty useful.
Beat me to it. The DOF preview button is a great tool. Simply press the button while looking through the VF to see what the DOF will be. It will darken the VF so use it in brighter conditions to really see the effects. Also if you have a flash attached to your camera the DOF preview button becomes a modeling light. Some cameras offer the ability to turn this feature off though.

[imhotep]

Also if you have a flash attached to your camera the DOF preview button becomes a modeling light. Some cameras offer the ability to turn this feature off though.

So does this mean that if my flash is attached, then the button will only illuminate the light and that the DOF preview feature is trumped?

[imhotep]

Once again...give "Understanding Exposure" by Bryan Peterson a read.

Thanks. Amazon here I come.

[In2Photos]

So does this mean that if my flash is attached, then the button will only illuminate the light and that the DOF preview feature is trumped?
I would have to check that. In reading my XT manual it states that the DOF preview button will also lock exposure. I wonder if this also refers to the flash exposure. I don't have anything handy right now but could check for you later.

[Billginthekeys]

have you tried using the DOF preview button on the camera? i've been finding that to be pretty useful.

Beat me to it. The DOF preview button is a great tool.
actually i beat you both to it in the second responce (only second because mine took longer to type than cdi's) :p

[In2Photos]

actually i beat you both to it in the second responce (only second because mine took longer to type than cdi's) :p
Tell you the truth yours was just too damn long to read.:p

[Billginthekeys]

Tell you the truth yours was just too damn long to read.:p
well as long as the OP doesnt think so :confused::D

[unix04]

Once again...give "Understanding Exposure" by Bryan Peterson a read. Great way to clear up those lingering questions. Remember that f/1 is a very narrow depth of field...just like the number 1 is very narrow.....f/22 is a wide depth of field...just like the number 22 is wider than the number 1.

i bought that book the other week and read through it. it's a very good book, but i was wondering about the whole metering against the sky/green concept he talks about.

would metering against the sky/green give my 30D the most accurate reading possible? he mentions something about -2/3 underexposure for digital cameras as well.... i was wondering how applicable this is to my camera.

[imhotep]

I would have to check that. In reading my XT manual it states that the DOF preview button will also lock exposure. I wonder if this also refers to the flash exposure. I don't have anything handy right now but could check for you later.

Well my 580ex comes in on Friday, so if nothing else, I can slap in the camera and see for myself :)

[Jason77]

Tell you the truth yours was just too damn long to read.:p

:D that's actually why i didn't notice it... i just skimmed it. :oops:

either way, billg and in2photos... very well put by both of you.

[In2Photos]

So does this mean that if my flash is attached, then the button will only illuminate the light and that the DOF preview feature is trumped?
Alright I just checked and with the flash attached the DOF preview still stops the lens down.

[Blue S2]

Easy,, F/1 is SUPER BLURRY, F/22 is very sharp. It gradually changes for all the numbers in between. Take a picture of one single object at each aperature and compare them. Study those shots a few times and see the difference. It will make a lot more sense afterwards.

[liza]

It will all become clear to you with practice. Keep shooting, and don't become discouraged! :)

[montreal]

I also found in the beginning that what I learned in books or on the forum was very difficult to apply in reality (I always ended up with at least one setting that was wrong... f. ex. ISO). But as the Lady in her prime says, it all comes with practice. It's much like learning a new language... in the beginning it's difficult to use the theory you have learned but you just have to jump into it and not be afraid. It will come.

[Lightstream]

Most of the time, the problem seems to center on my lack of mastery with setting my aperture. The kind of dissappoints I'm talking about are, for example, a background that is out of focus when I wanted it to be as sharp as the foreground. Sometimes it could be just the opposite - an entire table of decorations at a wedding is in focus, and all I wanted was for the rose closest to my lens to be sharp with the rest blurred.
:)


Couple of points - Are you using automatic focus point selection or center point only? Set it to center-only. Then focus on the subject that you want to be in focus. It doesn't sound like an aperture problem to me.

Second point - I had the same lens and its {mis}focusing was ALL over the place. If setting center point AF and pointing the center dot at the subject you want doesn't at least yield some decent results it may be the lens.

[StewartR]

Another useful resource for helping to understand aperture and depth of field is The SimCam (http://www.photonhead.com/simcam/).

[imhotep]

Couple of points - Are you using automatic focus point selection or center point only? Set it to center-only. Then focus on the subject that you want to be in focus. It doesn't sound like an aperture problem to me.

Second point - I had the same lens and its {mis}focusing was ALL over the place. If setting center point AF and pointing the center dot at the subject you want doesn't at least yield some decent results it may be the lens.

I have always used the center dot to focus. Which lens were you referring to, the Tokina 12-24 or the Tamron 28-75? So far my Tamron seems to be a pretty sharp copy.

[imhotep]

Another useful resource for helping to understand aperture and depth of field is The SimCam (http://www.photonhead.com/simcam/).

Pretty cool.