Portrait picture help

[KrypticChewie]

I'm really new to photography. I've been doing a little reading on the net and I've seen some cool portrait pictures with the background blurry. I have tried a couple using a Canon A720IS with a 2x zoom lens attached and different aperture sizes. I came up wit these but is there a way to get the background more blurry?
http://picasaweb.google.co.uk/KrypticChewie/TryingThePortraitThing

 

[Happy Hour]

Take you 2x teleconverter off. it doubles your aperture and you need a smaller aperture to get the blurry backgorund. set your lens to the smallest aperture that it can go say 3.5 or whatever it is. Then get as close to your subject as possible and that is as blurry as it gets!

 

[KrypticChewie]

Really? I read that to get blurry it helps if you zoom more and a telephoto lens helps. Are you saying that the teleconverter does not help as a teephoto lens does?

 

[dbrandon]

I would have said move your subject further from the background, but judging by the pics, the subject-background distance is already quite large. So maybe that's the best your going to get with that lens.

Telephotos are great for background blur, but i'm not sure of the technical qualities which make them so. Maybe it's the physical aperture size. E.g. a 200mm f2.8 lens is going to give a much more blured background than a 50mm f1.8, won't it :S I'm not sure !

 

[LaFoto]

As you can see, the background IS blurred (but working with such a long lens requires a lot more light than working with a normal lens, so you easily get motion blur since you can not longer hold your camera still enough for the exposure!), but even so, where there is the house and fence behind the person, you get so many recognisable structures that the background remains distracting. No matter if it is blurred or not. The other two photos are better in that respect, what with just the green on the hill as background.

You will find out that when you zoom out, your widest open aperture (smallest f-number) will become smaller than when the lens is put to "normal". Maybe you would want to try to stay in "normal" but use the widest opening (which might be f2.8 instead of f5.6 in the 2x zoom function).

To tell you the truth, I know too little about the camera you used, and don't quite get if you attached a converter or only just the in-built zoom function... so I cannot REALLY help.

But "neutral" backgrounds (just as only a green bush, or the sky) may also help you get in the right direction (use fill-flash when you make the bright blue sky your background!, i.e. switch on the flash even though you are out in bright daylight).

 

[Happy Hour]

I would have said move your subject further from the background, but judging by the pics, the subject-background distance is already quite large. So maybe that's the best your going to get with that lens.

Telephotos are great for background blur, but i'm not sure of the technical qualities which make them so. Maybe it's the physical aperture size. E.g. a 200mm f2.8 lens is going to give a much more blured background than a 50mm f1.8, won't it :S I'm not sure !

ummm... Your backwards 50mm F1.8 is going to give a blurrier picture than f2.8. now also I don't think were talking about a lens that has a f stop of 2.8 fully zoomed at 200mm!that would be around a $5,000 lens & if you can afford that lens you better know how to use it. I have a 75mm f2.8 taking a portrait with this lens and at f2.8 you cannot see anything in the background. Now if i take my 2x Teleconverter and put it on the camera before the lens it will now give me a f5.6 aperture which is not even close to being blurry compared to the f2.8. now if were talking about a teleconverter that screws on the front of the lens, it does not change your F stop but does lessen the quality of your picture! It's like using a magnifying glass It make everything bigger but it's more blurry than when you see the image with your own eyes. now if were talking about a P&S camera i think your out of luck! they focus more on trying to get everything in the picture the same rather than blurring out the background. at least mine does.

 

[dbrandon]

ummm... Your backwards 50mm F1.8 is going to give a blurrier picture than f2.8. now also I don't think were talking about a lens that has a f stop of 2.8 fully zoomed at 200mm!that would be around a $5,000 lens & if you can afford that lens you better know how to use it. I have a 75mm f2.8 taking a portrait with this lens and at f2.8 you cannot see anything in the background. Now if i take my 2x Teleconverter and put it on the camera before the lens it will now give me a f5.6 aperture which is not even close to being blurry compared to the f2.8. now if were talking about a teleconverter that screws on the front of the lens, it does not change your F stop but does lessen the quality of your picture! It's like using a magnifying glass It make everything bigger but it's more blurry than when you see the image with your own eyes. now if were talking about a P&S camera i think your out of luck! they focus more on trying to get everything in the picture the same rather than blurring out the background. at least mine does.

Hmmm are you sure ? I was just basing it on something like a 70-200 2.8 zoom, which has a much larger physical aperture at 200 wide open than a 50 1.8 would.

I could be all wrong, but i thought it was the actual size of the aperture that mattered for DOF.

Oh well, i dunno But yes you're quite right, anyone who can afford a lens like that will most likely know how to use it !

 

[Mav]

Focal length, aperture, and subject distance all come into play as far as depth of field goes. Also, a 200mm f/2.8 isn't $5000. Both Canon and Nikon make 80-200mm f/2.8 telephoto zooms at around $1000. You can also get telephoto f/2.8 primes at about 200mm FL's for less than that. Nikon's 200mm f/2 AF-S VR - now there's a $5000 lens. :mrgreen:

You can make just about any DOF calculation here: http://www.dofmaster.com/dofjs.html

 

[Happy Hour]

Focal length, aperture, and subject distance all come into play as far as depth of field goes. Also, a 200mm f/2.8 isn't $5000. Both Canon and Nikon make 80-200mm f/2.8 telephoto zooms at around $1000. You can also get telephoto f/2.8 primes at about 200mm FL's for less than that. Nikon's 200mm f/2 AF-S VR - now there's a $5000 lens. :mrgreen:

You can make just about any DOF calculation here: http://www.dofmaster.com/dofjs.html

sorry about that it was a example! It's 2,914.00 for my camera for a fixed f2.8. And again if you can dump that much on a lens and have no idea how to use it (Your a MORON!!!) And if you look at the pics I don't think your gonna get that poor of quality pic from a 1,000- 3,000 lens!But that wasn't my point. He said he is using a 2x teleconverter which doubles your f/stop So do the Math Mav, I can do any mathematical crap I want But it wont change the fact that your going to get a less blurrier background with the 2x teleconverter on your lens. I just took 2 pics 1 with and one without the teleconverter the one without is much more crisp,cleaner,and the DOF is much shallower!

 

[dbrandon]

sorry about that it was a example! It's 2,914.00 for my camera for a fixed f2.8. And again if you can dump that much on a lens and have no idea how to use it (Your a MORON!!!) And if you look at the pics I don't think your gonna get that poor of quality pic from a 1,000- 3,000 lens!But that wasn't my point. He said he is using a 2x teleconverter which doubles your f/stop So do the Math Mav, I can do any mathematical crap I want But it wont change the fact that your going to get a less blurrier background with the 2x teleconverter on your lens. I just took 2 pics 1 with and one without the teleconverter the one without is much more crisp,cleaner,and the DOF is much shallower!

But surely providing you move back to compensate for the increase in focal length, you will still get the identical DOF with or without the converter ?

I'm not trying to say this is right, 'cos i am trying to figure it all out too (i have never used a converter !).

But taking a 200 2.8 as an example ...

200*1/2.8 = 71.43 (no coverter)

400*1/5.6 = 71.43 (2x converter)

Surely they'd give the same DOF effect ? I am maybe missing something very obvious here ! So feel free to tell me im barking up the wrong tree completely !

 

[Happy Hour]

But surely providing you move back to compensate for the increase in focal length, you will still get the identical DOF with or without the converter ?

I'm not trying to say this is right, 'cos i am trying to figure it all out too (i have never used a converter !).

But taking a 200 2.8 as an example ...

200*1/2.8 = 71.43 (no coverter)

400*1/5.6 = 71.43 (2x converter)

Surely they'd give the same DOF effect ? I am maybe missing something very obvious here ! So feel free to tell me im barking up the wrong tree completely !

ok I'm not a math wizard. but anyone here will tell you a teleconverter is going to give you lesser results. I'm not going by math but by proper exposure. setting my camera at f2.8 Iso 100 and then using my meter to adjust the shutter speed. Then using a teleconverter 2x My aperture is now at 5.6 A SMALLER HOLE ALLOWING LESS LIGHT TO HIT THE SENSOR my shutter speed now changes to compensate for the smaller hole through the lens! (Aperture) this isn't rocket science, so don't over think it. smaller hole longer DOF Bigger hole SMALLER DOF

 

[dbrandon]

smaller hole longer DOF Bigger hole SMALLER DOF

That's where i was coming from with my initial statement.

A 200mm 2.8 has a 'hole' 71mm in diameter.

A 50mm 1.8 has a 'hole' 27mm in diameter.

(i think !), so i just assumed the 200mm would give a blurrier background (shallower dof)

 

[Happy Hour]

your backwards 1.8 is a bigger hole than a 2.8 exactly double the size so if 2.8 has a 1/2" hole a 1.8 would be 1" <- just a example.not the real measurement! have you read understanding exposure?

 

[dbrandon]

What you say is right, based on the focal length being the same. But from my understanding, the aperture is dependant on the focal length.

f1.8 means that the holes diameter is 1/1.8 of the focal length which = 27mm on a 50mm lens. Do the same calculation for the 200mm, and the hole is much larger.

I have not read that book no, and it may well be useful for me to !

But i have read numerous sources on the internet, and thats my understanding of it. This was the one that got me thinking http://www.kate-harris.co.uk/technical-terms-aperture-basically-explained-7

 

[Happy Hour]

What you say is right, based on the focal length being the same. But from my understanding, the aperture is dependant on the focal length.

f1.8 means that the holes diameter is 1/1.8 of the focal length which = 27mm on a 50mm lens. Do the same calculation for the 200mm, and the hole is much larger.

I have not read that book no, and it may well be useful for me to !

But i have read numerous sources on the internet, and thats my understanding of it. This was the one that got me thinking http://www.kate-harris.co.uk/technical-terms-aperture-basically-explained-7

I have a 50mm @f/5.6 and a lens zoomed out to 200mm @f5.6 now I'm holding these side by side right in front of me right now,and the aperture blade holes look identical to me! now maybe on a 3 foot long $3,000 Canon lens I'm sure it's a bigger hole but do you have one? because i doubt the majority of people on here have one! So on everyday lenses use by the average person I do not think that is true! Actually I have 12 lenses here and every one I'm checking the hole looks to be the same size 2 f/5.6 I'm using this because all my lenses will at least stop down to this aperture. But F/5.6 is not a bigger hole on my 400mm lens than on my 50mm macro lensor my 28mm wide angle lens the hole all looks to be the exact same size at that aperture. Ok i just read your link and it completely backs up everything I have said! What are you reading that is telling you different?