NTP Challenge: Aperture and Depth of Field (DOF)

[ricktas]

As it has been a while since we did this challenge, and we have had quite a few members join to learn how to use their shiny new camera's with more control over the results, it is time to give the NTP challenges another round.

Our 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 (or larger - remember smaller F stop numbers are actually bigger apertures) and one at f22, of the same subject.

Post both photos in this thread, with comments about what differences you notice between the two photos , what the effect of aperture had on the shutter speed, and how you could use this difference to make your future photography more creative.

Looking forward to seeing the results and discussion.

[bigdazzler]

You really do put a big effort into helping the newcomers to the game Rick .. for that you should be applauded mate, well done.

[ricktas]

Thanks Darren. It is a bit of a balancing act, between encouraging new members to join in and learn, and also providing something challenging for the experienced members as well.

[bigdazzler]

I bet it is .. the simplicity of these challenges is the key, both in as far as whats required to complete them and the way they are set out and explained. Id imagine thats gold for people that are totally new to all of this jargon that we throw around.

[seastorm]

Thanks Rick, this is great!! Nothing like a challenge now and again to help speed up the learning process, I think of it like an exam or assignment

Now, to find a subject.....

[bigdazzler]

Now, to find a subject.....

thats the thing about Aperture and DOF .. its one of the most basic fundamentals, yet arguably the most creative aspect of SLR photography .. you can make just about anything interesting by mixing it up

[seastorm]

Right-o, here's my contribution. I took 2 photos, one on f/2.8, and the other f/32. I thought I'd use a waterfall as my subject, that way the differences are very noticeable between the 2 apertures.

The photos are taken with my D40, Aperture setting, and the Tamron 90mm f/2.8 Macro lens.

Photo 1, f/2.8.
Photo 2, f/32. (Sorry Rick, I forgot it was supposed to be f/22, I just turned it to the max f. number allowed on my camera....)

I can see that in Photo 1, the shutter speed is very fast, hence the water drops are very noticeable, it gives the impression that the movement is frozen in time. Also the depth of field is around the water - the foreground and background objects are blurred. Because the shutter speed was fast (1/800 sec), the image was a bit on the dark side. To counter this, I would need to either slow down the shutter speed, or possibly choose a higher ISO?? (please correct me if I'm wrong here).

In Photo 2, just about everything in the photo is in focus, and the water looks like it's flowing, ie it gives the impression of movement. Because the aperture is on f/32 (ie small), the camera thinks it needs more light, so it slows down the shutter speed (down to 1/6 seconds). The depth of field is way much larger than with a smaller f number.

I would use a small f number (narrow depth of field) if I want to draw a person's attention to a particular area of the photo, ie bring out the subject a bit more to the viewer. A slower shutter speed give the impression of movement, and a fast shutter speed and large aperture to make everything crystal clear in the picture and freeze movement.

[Kym]

Dramatic difference! Excellent example of both DoF and shutter speed.

[seastorm]

Excellent example of both DoF and shutter speed.

Thanks Kym!!

Hopefully my little contribution will help others as well, I tend to learn faster if I can see it rather than read about it

[ricktas]

Good work. You mention slowing the shutter speed down for the first and raise the issue of changing either the shutter speed or the ISO. Increasing the ISO will increase the shutter speed even more. A higher ISO will counter a dark photo, given you keep the Aperture and shutter speed the same. Yes you can slow the shutter speed, but you risk an over-exposed photo then.

You have just discovered the exposure triangle. ISO / Shutter speed / Aperture are all inherently linked. Each one can be adjusted independently of the others, but all three need to be considered to get a correctly and creatively exposed photo.

[seastorm]

Thanks, Rick

I think I'll need to do some more experimenting because I'm still a little bit unsure how ISOs affect a photo.

But yeah, with regards to the exposure triangle, it's one of those formulas (or is it formulae?) that photographers need to consider. I read somewhere that photography is a mix of art and science, I suppose this is the scientific part of it.

[Kym]

I think I'll need to do some more experimenting because I'm still a little bit unsure how ISOs affect a photo.
But yeah, with regards to the exposure triangle, it's one of those formulas (or is it formulae?) that photographers need to consider. I read somewhere that photography is a mix of art and science, I suppose this is the scientific part of it.

This thread explains it. http://www.ausphotography.net.au/for...ad.php?t=24079
Post #2 of that thread shows the relationship in a diagram.

Back in the day ISO (aka ASA aka DIN) was the rating of speed of film (how reactive to light the film was).

In the digital they kept the same ISO scale and applied it to the sensor and the level of amplification of the sensor signal.

So a film camera set up with ISO 400 film, f/16, and 1/125 second exposure should produce an image print of very similar exposure (assuming default processing) to a digital camera on the same settings.

[seastorm]

Thanks, Kym, I like diagrams, it helps me understand faster I will read up on it.

Cheers, all!!!

Actually, where are all the others? Please, please get involved and contribute to this thread, it will certainly help others and will definitely help you, I've learnt a bit more already!!!

[wandera]

Ok here goes, my first attempt at one of your challenges:
Both photos taken tonight about 5.30pm, at our fish pond water fall in our yard, home made pond & fall.
Camera Olympus E-410 First photo; F Stop f/4.2 Exposure time 1/60 sec iso was 1600 (opps didn't check that before taking photo) focal lenth 48mm Metering mode pattern
Second photo F stop f/22 Exposure 1/2 sec all other things the same.
I am facinated in the difference in colour & light between the two photos, I used a tripod & did not move between photos. so now let me learn what I did right & what I did wrong. thank you for this segment as I realy want to learn & don't have the funds to do a course
Keep up your great work it is appreciated

[etherial]

Somethings not right here, I wouldn't have expected such a huge difference in color between these two shots?

[seastorm]

There seems to be a lot of noise, I'd say due to the high ISO. Photo 2 also seems to be a bit overexposed.

Can somebody verify what I mentioned please, I'm still learning myself..

[ricktas]

Agree something else is going on here Deb. Cause you didnt include EXIF with your photos it is hard for us to tell what is happening. You mention ISO 1600 for the first photo, did you fix that for the second? If so, it is hard to compare the two. You will probably need to try again with the same ISO on both.

[shaggydog]

G'day,

I have been slowly plugging away at the aperture challenge for a while now. I'm a little frustrated (but not disheartened).
Maybe foolishly, I chose people as my subject(s). Unfortunately, although I am choosing to change only the aperture (as per the challenge), I find the camera often meters differently between shots.
I feel I need to have a better understanding of many more aspects of the camera than just aperture to be successfully completing this challenge (or maybe just choose a less dynamic subject and composure).
I'm really only posting this as I received an email from the forum telling me to post more messages. However I hope this makes some other struggling newbies feel a bit better too.

Cheers

[ricktas]

G'day,

I have been slowly plugging away at the aperture challenge for a while now. I'm a little frustrated (but not disheartened).
Maybe foolishly, I chose people as my subject(s). Unfortunately, although I am choosing to change only the aperture (as per the challenge), I find the camera often meters differently between shots.
I feel I need to have a better understanding of many more aspects of the camera than just aperture to be successfully completing this challenge (or maybe just choose a less dynamic subject and composure).
I'm really only posting this as I received an email from the forum telling me to post more messages. However I hope this makes some other struggling newbies feel a bit better too.

Cheers

Hey, firstly you dont need more understanding of your camera to do this challenge. That is the idea of the NTP forum, you learn one camera feature, then move onto the next and then start combining them. All the while learning what each function and part does.

Aperture affects depth of field, so if your people subjects are close to the chosen background etc, you will not notice as much variation as you would if they are several metres from the background.

Post some examples of what is happening and we can guide you on your way.

[shaggydog]

Thanks Rick,

I just managed to get something today that I think will show the DoF changes the aperture challenge is looking for. It will also (but not strikingly), show some of the problems I was mentioning...

I notice that even though the shutter speed automatically varies to account for the change in aperture, there still appears to be a change in the overall colour of the photo. I'm not clever enough to specify this change, but it seems like a slightly different exposure (on the wider aperture, the picture appears lighter than on the smaller aperture, even with the adjustment in exposure time).
Not seen in these pictures, as the lizard was very accommodating and sat still, is the introduction of motion artefact with smaller apertures (obviously due to longer exposure time). I struggle with this when taking pictures of people, but as you mentioned Rick, that's for another topic...

My camera: Canon EOS 50D
Lens: 24-105mm f/4L IS USM
For these pictures:
The constants: Focal length 105mm; ISO 400; flash not fired; hand held
Picture 1: Aperture f/4; Shutter Speed 1/2000
Picture 2: Aperture f/22; Shutter Speed 1/60