Challenge I - Aperture and Depth of Field

[ricktas]

Our first challenge to our members that want to learn to take control of their digital camera is based on the Learning Centre topic : Experimenting with Aperture

We would like you to set your camera to Aperture mode (sometimes called A or Av mode). Check your camera manual in need, on how to set your camera to Aperture mode.

We want you to go out and take two photos of the same subject. One at the largest aperture your lens will allow and one at the smallest. So take one photo at f4.5 and one at f22, of the same subject. Then post both photos in this thread, with comments about what differences you notice between the two photos.

[clm738]

f4.5
only Noah in focus
shutter 1/160
file size 63.4kb

f22
more people in focus
shutter 1/6
file size 85.7kb

[clm738]

Have now also noticed exposure difference

[Jcas]

F4.5 Background not focused
F22 Background in focus.

[bigdazzler]

with these, remember distance between subject and background has a great effect on DOF also ..

[ricktas]

So if you wanted to take a nice portrait shot of a friend, given the above tests, what aperture would you use, and how would you place your subject in relation to the background?

[Seven]

Im thinking with portraits the background needs to be blurry in someway.

So I would have a f4.5 to 8 and try to have the backdrop blurred out. If I was to have a high f20 or something the background would be more in focus and take away from the portrait.

However if there was something nice behind them or it was a portrait of someone standing in front of a place of interest eg holiday snaps of places you have been I would select the background to be blurred. Slightly maybe but not as much if I was taking a portrait.

I would hopefully still in a portrait get something with structure behind them like nice set of rocks or colored things that don't over power the person.

Oh and focus on the eyes and nose with spot meter to grab the settings based on the important part. Probably would try to get lighting right and find out side better as still getting used to flashes

[Seven]

Went out and did the challenge and found some interesting things that I worked out.

First photos definitely showed how you can get blurred back ground to keep the attention on the part of picture you want the attention.

The second set shows when working with a flash how it totally affects the photo contrast. I was amazed at the level of contrast difference and it also gave me a better understanding of focal points of the lenses.

I also found that the lens needed at least a few cms of distance between the point of interest to the focused part. Yet with my bigger zoom lens its not as bad.

Further more to previous post I would also have at least 30cm to 1 mt distance between background and the portrait shot.


I also cropped in on the leave to show some sort of reasoning behind just cropping the point of interest, but still having a blurred background

Something I also noticed was that the image slightly looked a bit more zoomed in with out changing the zoom and not quite sure why?

[clm738]

Hi Rick
I would use a large aperture and place them some distance from the background to make it more OOF.

[NikonNellie]

With a close portrait you would want your subject to be the main point of interest and your background OOF so that the viewer's eye is not distracted elsewhere in the shot. I would therefore set my aperture to the largest setting that the camera would allow, e.g f4.5 ( even larger if your camera will allow it). I would have them standing close to the background.
If you want your subject to be a part of a scene ( say standing in front of an historic building) then I would have them stand further away from the background and set my aperture to a smaller setting e.g. f22, critically focus on my subject and not the building. I should then have a shot where both my subject and the background are in focus.
I HOPE THIS IS CORRECT!

[NikonNellie]

42 Degrees in Sydney today so I did not venture outside to take my photos instead I took a couple of shots inside. The first one was f5.6, which was the largest aperture my lens would allow. The second photo was f22. Both photos had an ISO of 125 and I used the natural light coming in through the window. The venetian blinds are probably not the best background but you can distinguish that one background is crisper than the other.

[ricktas]

Good work everyone. So now you are learning what Aperture does, and will be able to creatively use it to change the way your photo looks. It is a bit more complex than just choosing an aperture though.

The other parts of the equation is the distances objects are from the camera, AND the aperture selected. Remember DOF means Depth Of Field, the distance front to back in your photo that will be in focus, from the focal point, at a given aperture. The last component to affect the DOF, is the focal length of a lens, a Lens at 50mm and f4.0 will have a different DOF to the same lens at 200mm and f4.0

Take this example:

Your subject is 2 metres from your camera
You are using a 50mm f1.8 lens (the great standard portrait lens) and its reasonably cheap to buy.

Here is a chart that shows what happens as you change aperture:

At F1.8 you focus on the subject at 2 metres, your DOF will be from 1.92m - 2.09m
At F2.8 you focus on the subject at 2 metres, your DOF will be from 1.87m - 2.14m
At F4.5 you focus on the subject at 2 metres, your DOF will be from 1.81m - 2.24m
At F8.0 you focus on the subject at 2 metres, your DOF will be from 1.68m - 2.48m
At F16.0 you focus on the subject at 2 metres, your DOF will be from 1.45m - 3.25m

So as you go to a smaller Aperture (larger F number) the distance front to back that is in focus is greater, so to effectively blur your background, you background will need to be further back from your subject.

But there is another additional aspect, and that is how far your subject is from you. Taking the example above again, but moving your subject to 5 metres away.

At F1.8 you focus on the subject at 5 metres, your DOF will be from 4.51m - 5.61m
At F2.8 you focus on the subject at 5 metres, your DOF will be from 3.94m - 6.85m
At F16.0 you focus on the subject at 5 metres, your DOF will be from 2.55m - 122.45m

So the further the distance from the camera to the subject, the greater the DOF.

Using Aperture effectively takes practice to know when to use it, how to use it and how to judge the DOF for your setting, so that you can make the background sharp or blurry, as you intend.

You can get small software programmes that calculate the DOF, using the focal length (lens), Aperture and subject distance. With that information they can calculate the near DOF limit, the Far DOF limit, the total depth and more. But who wants to cart a laptop and run some software everytime they need to know a DOF? The best way is to get out and practice in the real world, and learn from your results.

There several other factors that affect DOF, including the camera you are using (sensor size), There is quite a good DOF calculator here, but don't get to hung up on using it, try it to get an understanding, but you will learn more by getting out with your camera and taking shots for yourself.

[clm738]

Thanks Rick. What I do is to take most photos using a small aperture then the same photo using a large aperture and compare the two to try and learn how much is in focus and how to get the effect I want.Oh the joy of digital!!!

[Nanny]

I can see the difference in the background
in the first the background is blurred and the second is focused
and there is a difference in shutter speed.

[ricktas]

When in Av mode (aperture mode) and you change the aperture, the shutter speed adjusts accordingly, by the camera. At f4.5 the aperture is wide open so a lot of light can come through the lens to hit the sensor. The camera knows this so will select a faster shutter speed to ensure a correct exposure. When you take your shot at f22, the aperture opening is tiny, and the camera compensates by slowing the shutter speed to allow enough light through the small aperture, to again get a correct exposure.

Nanny has commented on this, and it teaches you that shutter speed and aperture are inter-related. When you start using manual mode, you will have to select both the aperture and the shutter speed. So it is worth understanding the relationship between the two now, while we are still working in Aperture mode.

[Nic076]

Great thread Rick. I have seen the difference quite a few times in many of my photos when I want a little more detail but suddenly need to be aware of the amount of light on the subject. Generally I have had to up the ISO to compensate.

I also took some photos for a friend a little while ago of her little girl. We were at a park and it was quite bright, and the lens I was using, although set to largest aperture was catching too much background detail. I then realised what you just mentioned about distance. By changing where she was sitting and how close the trees were behind her I managed to get them quite a bit OOF. It was really just trial and error at the time, but a good tip to remember.

[Jcas]

Thanks for the example, it all helps, cute little girl too

[lourdes]

Thank you for this, i can see it now.

[ricktas]

Does anyone have any questions regarding Aperture and using Av mode? Please feel free to ask anything. Even if you think its a silly question. The only way to get the answer is to ask.

[chelle]

i had a play with the aperture today (got myself a camera but i'll talk about that later... this first challenge is more interesting).
I noticed a few fun things. I knew what to expect already having read this thread but i took a gazillion photos of all sorts of different things just to see what happened.
These are my most "ah ha" moments....

The mandarin tree gave the proper result IMO. Small aperture, nice small focus area with the background nice and blurry.

But the ones of DS2 at the fence was interesting to me cos it showed me how much a plain boring photo could still be improved just by using a different aperture. The blurry large aperture photo reminds me of some of the results i got from my p&s and the smaller aperture photo has so much more definition in the subject.

And then the one i took inside in a lower light situation was really cool. It is something that i am going to make a mental note of and play around with in the future. The ghost image sort of effort makes me wonder if there are situations where i could do this deliberately ... ? Maybe not! LOL! but if i get a tripod down the track it's something i might fiddle with. Either way it made it totally obvious how the increased shutter opening time is effected by changing the aperture.