Full body portrait with shallow DOF?

[Youhong]

hmmm.... personally think that technical aspect is very important... one can paint a very beautiful picture in mind but may not be able to reproduce it on a "hard copy" because of the lack of skills or knowledge to get it... :think:

 

[oneheart]

hee.. didnt even know there's this thing called the DOF calculator.. amazing!
btw, if i get a sigma 70-300mm f/4-5.6 APO DG macro, will i be able to get the effect? I understand that i'll need to stand quite far fr my subject in this case.. but i thot this is quite a multi purpose lens since it can zoom very far, it means i can shoot things like birds and it does macro too. If it has a long focal length, can i use it for full body portrait?
Thanks so much!

 

[Astin]

Using DOF Calculator without understanding DOF is like, hmmmmm :think:

 

[Deadpoet]

What we have here are tech geeks who feels that they know how to shoot beautiful photographs. The technical aspect of photography is of course important, but it is not the most important, it is just one of the many things.

Spending time calculating the DOF, might as well spent it on things that will yield a better and more beautiful picture.

 

[D70sshooter]

hee.. didnt even know there's this thing called the DOF calculator.. amazing!
btw, if i get a sigma 70-300mm f/4-5.6 APO DG macro, will i be able to get the effect? I understand that i'll need to stand quite far fr my subject in this case.. but i thot this is quite a multi purpose lens since it can zoom very far, it means i can shoot things like birds and it does macro too. If it has a long focal length, can i use it for full body portrait?
Thanks so much!

I think better place your subject far from the background. At 300mm, you have to shoot from far, and slight movement will produce blur picture.

 

[evershine]

oneheart, usually people shoot portrait using F/2.8 and lower.

Clockunder already answer your query..."if i get a sigma 70-300mm f/4-5.6 APO DG macro, will i be able to get the effect?"

QUOTE
But then, I don't think you can find any very long telephoto lens with aperture bigger than F/2.8. Moreover, even a F/2.8 for long telephoto lens is very very heavy and expensive. That is why some serious portrait photographers still prefer full frame in order to get the shallow DOF which they can get with a relatively short focal length lens and a very large aperture.

UNQUOTE

.

 

[Astin]

hmmm.... personally think that technical aspect is very important... one can paint a very beautiful picture in mind but may not be able to reproduce it on a "hard copy" because of the lack of skills or knowledge to get it... :think:

Any physics teacher can explain DOF, that does not imply that any physics teachers are photographers.
(on a lighter side, any maths teacher can explain how to win in casino, but that does not imply maths teachers are gamblers...)

 

[DeSwitch]

if yr background is far from yr subject, you will have nice bokeh. else just use photoshop to create the effect. The free Picasa does it well too.

in theory, shorter focal length will have a deeper DOF than tele lens at the same aperture setting. so a tele does helps to give you better bokeh IMHO.


I'm a total newbie so i may be wrong.

 

[oneheart]

if yr background is far from yr subject, you will have nice bokeh. else just use photoshop to create the effect. The free Picasa does it well too.

in theory, shorter focal length will have a deeper DOF than tele lens at the same aperture setting. so a tele does helps to give you better bokeh IMHO.


I'm a total newbie so i may be wrong.

so sorry, just to clarify.. u said shorter focal length will give DEEPER DOF, so the longer i go, like 200mm, i will get a SHALLOWER DOF?

 

[Gunjack]

Yes indeed. But it does not equate to better bokeh, but rather shallower DOF and bringing the background closer in respect to the subject...

 

[DeSwitch]

the bokeh will also depends on the quality of the lens used, what yr BG is. With a messy BG, you wont get nice bokeh.

http://deswitch.multiply.com/photos/photo/62/46

only used Picasa to get this effect. i dont shoot models. more of a nature shooter so those gurus please dont attack me for poor shots ok. Just want to point out that post processing can bring out the effect too.:sweat:

 

[oneheart]

Yes indeed. But it does not equate to better bokeh, but rather shallower DOF and bringing the background closer in respect to the subject...

shallow DOF != better bokeh. Shallow DOF does not equal better bokeh because it depends on ur background?

 

[Galdor]

Hi Sis,

I think what he meant is, to get a good bokeh the background must be clean and blur rather than messy and blur while keeping your subject sharp. Hope I interpreted it correctly and you can understand what i am saying.

 

[ortega]

factors for less DOF

1. focal lenght - the longer the focal lenght the less DOF you get
2. aperture - the bigger the aperture (smaller f stop) the less DOF you get
3. camera to subject distance - the closer the distance the less DOF you get

other stuff for better bokeh
subject to bg distance - the further the better

 

[bigboy_cad]

Try this link, hope can help to everybody.

http://www.photonhead.com/exposure/exposure.php

 

[kzone]

1 & 3 seems to be inversely related, if long focal length then need to stand further away.. & if stand close than need wide angle... hmm.. how ah?

 

[Splutter]

I guess you can say 1&3 are inversely related, but quite a few tele lens have rather large min focusing distance, so it'll mean you can't get close even if you want to. Unfortunately for taking shots of people, I would say aperture is the most important factor that affects the so called "blur". There's actually a 4th factor, the sensor size which is actually the most important, but in the digital age, most of us are stuck in 35mm format since medium format and above are horrendously expensive.

Some shots taken using F1.2-F1.6 on 85mm
http://forums.clubsnap.org/showthread.php?t=232698

 

[kzone]

Ic... so a 300mm f/2.8 is a gd lens ro got bokeh effect but u have to stand far far away?

 

[Splutter]

Yes. Not to mention perspective change. Let's say you wan to show a mansion behind the model but want it to be "blur", it's not really practical to shoot with a 300mm in such scenarios since if you want the model to fit the frame, the background would probably be just a tiny part of the mansion.

 

[lastboltnut]

Hi, Clockunder, I think you have made a mistake here. A 50mm lens remains a 50mm lens when come to DOF calculation, it doesn't change with the Crop Factor (CF). Only Field Of View (FOV) changes with CF. So, when you calculate the DOF for DSLR, use the actual lens focal length....in this case 50mm, not 50xCF...

I do not have any experience using a DSLR taking portraits. I just know that around 85mm on 35mm format equivalent is ideal for taking full body portraits standing abut 5m away. If F/1.8 is used, then the DOF is about 0.36m (0.18m infront and 0.18m behind) and you get a very shallow DOF to have a blur background and the subject appears almost completely isolated.

Apparently, if you are using an APS-sized DSLR and want to maintain a similar shallow DOF, you would need to use a longer focal length and/or go closer and/or use a bigger aperture according to DOF. But then in order to maintain the same composition, you need to go further away instead of nearer. However, the longer focal length used to get a shallower DOF is negated by the further distance. (Use a DOF calculator to see what I mean).

For e.g. APS sized DSLR with a crop factor of 1.6x.
Focal length = 50mm
Distance necessary to mainain composition as 85mm on full frame= about 5m (about same as full frame because 50mm x 1.6 = 80mm on 35mm equivalent format)
Aperture = F/1.8
DOF = 0.67m (0.31m infront, 0.36 behind)

Focal length = 85mm
Distance necessary to mainain composition= 8m
Aperture = F/1.8
DOF = 0.59m (0.29m infront, 0.30 behind)

Focal length = 120mm
Distance necessary to mainain composition= 11m
Aperture = F/1.8
DOF = 0.56m (0.27m infront, 0.29 behind)

The decrease in DOF is very marginal because the shallower DOF of using a long focal length is offset by a need to move further away from the subject to maintain composition. So unless you can use a much bigger aperture, you won't be able to get a DOF as shallow as can be achieved on a full frame.

But then, I don't think you can find any very long telephoto lens with aperture bigger than F/2.8. Moreover, even a F/2.8 for long telephoto lens is very very heavy and expensive. That is why some serious portrait photographers still prefer full frame in order to get the shallow DOF which they can get with a relatively short focal length lens and a very large aperture.

So in the end, the practical way out for APS-sized sensor DSLRs is to have the subject stand further away from the background nad have a cleaner (i.e. not too cluttered background.