Please help with setting f number in Canon EOS350 Rebel XT

sunny79 · 27th April 2009

Hello everyone! I am a newbie, both to this forum and to SLR photography. I have a little baby on the way and so, I really want to figure out how to take photos where my subject is sharp and distinct and the rest of the background is blurred. I have a Canon EOS 350D digital rebel XT. Till now, I have used only the automatic modes.

I read the manual and figured out that I need to use the AV mode. So, I turned the camera on, set the dial to the AV mode. Then, I looked at the LCD display and turned the wheel (next to the shutter button). This is when I got really confused. I would really appreciate your responses to my questions below -

1) By turning the wheel, a number on the LCD display either increases or decreases. Is this the aperture value?

2) How do I translate the aperture value into an F number? Most of the manuals I read about setting the aperture only talk about F/stop values. What aperture number does an F stop of 2.8 translate to?

3)I am only using the standard EFS18-55mm that the camera came with. I cannot invest in pricier lenses for the next few months. Do you think I can take any pictures with the subject clearly against a blurred background with this lens?

4) What kind aperture value would you recommend for photographing a child in a sunny park?

Thank you so so much!

Dream Merchant · 27th April 2009

If you're looking at numbers like 3.2, 3.5, 4, 4.5 etc, yes, that's the aperture value.

Just set it to the smallest NUMBER you can, and be sure to select the AF point that goes over your baby's eye, or whichever part you want sharp.

'2.8' is an aperture value. By itself, it does not translate to another value.

Yes, just use your kit lens. Set the aperture as described above. Go as close to baby as possible. You will naturally NOT get the same degree or smoothness of 'blurred background' (boke or bokeh), but since you mentioned not being able to afford another lens at the moment, just maximise what you have.

In sunny parks, you could stop down the lens to f/5.6 or f/8 if you don't mind the background being more in focus. That will give you your lense's 'optimum' sharpness and contrast (more or less) and probably cover minor focusing errors.

The EASIEST thing you can do before baby arrives, is SHOOT and PRACTISE A LOT in the same exact location/conditions that you will likley be photographing baby at/under. You could also see if you can borrow something like a 50mm f/1.4 or f/1.8 lens from a friend for awhile. It will make your life much easier when photographing baby in less than ideally lit conditions and also offer better overall performance and bokeh than your kit lens.

Hope this helps some and CONGRATS!

CS TAN · 27th April 2009

I think with your kit lens, the best you can go is f/3.5 (wide) and f/5.6 (long) if you want to create 'blur' background.

Like what Dream Merchant said, get as close to the baby as you can. You will need to have some distance between the baby and the background to create the bokeh effect. Since the baby is always lying down so it is quite hard to create this distance. Perhaps you can get your wife to hold the baby if you want to create the 'blur' background.

sunny79 · 27th April 2009

Thank you so much for your responses. So, for setting F value to 3.5, what is the aperture value I should choose on the lcd? After looking at the manual, I thought the F value and aperture number are inversely proportional to each other?

ahbian · 27th April 2009

Originally Posted by sunny79

Thank you so much for your responses. So, for setting F value to 3.5, what is the aperture value I should choose on the lcd? After looking at the manual, I thought the F value and aperture number are inversely proportional to each other?

Your LCD is displaying the F/value, so just set it to 3.5. It means f/3.5.

Dream Merchant · 27th April 2009

See my earlier post.

Numbers like 3.5, 4, 5.6 and sometimes in between like 3.2 ARE the aperture values, or rather, designation. I would suggest getting into the physics and mechanics only a bit later on, if your main objective for the near future is to get nice or decent photos of the coming baby.

But it's GREAT that you're interested! Not many photographers are.

27th April 2009	#1
sunny79 New Member Join Date: Apr 2009 Posts: 2	Please help with setting f number in Canon EOS350 Rebel XT Hello everyone! I am a newbie, both to this forum and to SLR photography. I have a little baby on the way and so, I really want to figure out how to take photos where my subject is sharp and distinct and the rest of the background is blurred. I have a Canon EOS 350D digital rebel XT. Till now, I have used only the automatic modes. I read the manual and figured out that I need to use the AV mode. So, I turned the camera on, set the dial to the AV mode. Then, I looked at the LCD display and turned the wheel (next to the shutter button). This is when I got really confused. I would really appreciate your responses to my questions below - 1) By turning the wheel, a number on the LCD display either increases or decreases. Is this the aperture value? 2) How do I translate the aperture value into an F number? Most of the manuals I read about setting the aperture only talk about F/stop values. What aperture number does an F stop of 2.8 translate to? 3)I am only using the standard EFS18-55mm that the camera came with. I cannot invest in pricier lenses for the next few months. Do you think I can take any pictures with the subject clearly against a blurred background with this lens? 4) What kind aperture value would you recommend for photographing a child in a sunny park? Thank you so so much!

27th April 2009	#2
Dream Merchant Member Join Date: Jan 2007 Posts: 4,150	Re: Please help with setting f number in Canon EOS350 Rebel XT If you're looking at numbers like 3.2, 3.5, 4, 4.5 etc, yes, that's the aperture value. Just set it to the smallest NUMBER you can, and be sure to select the AF point that goes over your baby's eye, or whichever part you want sharp. '2.8' is an aperture value. By itself, it does not translate to another value. Yes, just use your kit lens. Set the aperture as described above. Go as close to baby as possible. You will naturally NOT get the same degree or smoothness of 'blurred background' (boke or bokeh), but since you mentioned not being able to afford another lens at the moment, just maximise what you have. In sunny parks, you could stop down the lens to f/5.6 or f/8 if you don't mind the background being more in focus. That will give you your lense's 'optimum' sharpness and contrast (more or less) and probably cover minor focusing errors. *The EASIEST thing you can do before baby arrives, is SHOOT and PRACTISE A LOT in the same exact location/conditions that you will likley be photographing baby at/under.* You could also see if you can borrow something like a 50mm f/1.4 or f/1.8 lens from a friend for awhile. It will make your life much easier when photographing baby in less than ideally lit conditions and also offer better overall performance and bokeh than your kit lens. Hope this helps some and CONGRATS!

27th April 2009	#3
CS TAN Member Join Date: Sep 2007 Location: West Posts: 2,147	Re: Please help with setting f number in Canon EOS350 Rebel XT I think with your kit lens, the best you can go is f/3.5 (wide) and f/5.6 (long) if you want to create 'blur' background. Like what Dream Merchant said, get as close to the baby as you can. You will need to have some distance between the baby and the background to create the bokeh effect. Since the baby is always lying down so it is quite hard to create this distance. Perhaps you can get your wife to hold the baby if you want to create the 'blur' background.

27th April 2009	#4
sunny79 New Member Join Date: Apr 2009 Posts: 2	Re: Please help with setting f number in Canon EOS350 Rebel XT Thank you so much for your responses. So, for setting F value to 3.5, what is the aperture value I should choose on the lcd? After looking at the manual, I thought the F value and aperture number are inversely proportional to each other?

27th April 2009	#6
Dream Merchant Member Join Date: Jan 2007 Posts: 4,150	Re: Please help with setting f number in Canon EOS350 Rebel XT See my earlier post. Numbers like 3.5, 4, 5.6 and sometimes in between like 3.2 ARE the aperture values, or rather, designation. I would suggest getting into the physics and mechanics only a bit later on, if your main objective for the near future is to get nice or decent photos of the coming baby. But it's GREAT that you're interested! Not many photographers are.