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wide aperture vs postprocessing for shallow DOF

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Bezbozny

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I hear about many people buying very expensive lenses in order to produce a shallow DOF in the portraits and i would like to ask if there is a difference in obtaining the same effect with a little post processing in photoshop. I am thinking of buying the sigma 50mm 1.4 for my canon 40D buy i am thinking if at the end the result will be the same and i will be throwing money for no reason. I am not a pro so i dont make money from my pics and i am not rich either to buy expensive glass easily.

Another thing that i would like to add is that with a smaller aperture you get sharper image and by postprocessing the background you get both a very sharp image and a shallow DOF, while from what i read many lenses are not very sharp when they are wide open.

I know that the real thing is always bettr than faking it...but at the end of the day...is there a really huge difference?

Thank you in advance,

Bezbozny.
 
In theory there is nothing that says you can't. The question is just how much time you need to spend on it. You probably need to spend a lot of time on EACH pictures if you want to have something even only half decent. I would much rather just use a fast lens. Some of the fast primes are not that expensive it's well worth the investment.
 
The 50mm f/1.4 isn't all that expensive of a lens ($340 US) and will allow you to take pictures in much darker conditions than you could do at f/5.6 or f/8. Of course, you can still use the f/1.4 at f/8 if you want but you can't use an f/5.6 lens at f/1.4.

It would seem to me to be a lot of unnecessary work to blur the background in post-processing when you could buy a sharp, fast lens that will do it all for you.

As an alternative, you could buy the 50mm f/1.8. It is very cheap and still much faster than the kit zoom (if that is what you have).
 
IMO It's pretty challenging to add DOF via PP. I've been a Photoshop user since v6 and I can tell you there is no guaranteed way to mimic the effect. If your subject cannot be well masked (outline selected), it'll never work. Even when it does work it generally has a 'fake' feel to it in comparison to the real thing.

The amount of time required to add DOF to an image PP compared to just using the lens features is drastically different.

If you're really interested in a nice bokeh and DOF, go with the real effect. You could spend up to an hour on one image trying to add it PP.
 
Bezbozny said:
[…] i would like to ask if there is a difference in obtaining the same effect with a little post processing in photoshop. […]
Click to expand...
ok, but then you're "photoshoping" and not "photographing", no?

food for thought, i'd say!
--
regards, alexandre
 
In certain very simple cases you can do it. The subject must be easy to isolate - with a reasonably simple outline. Hair? Forget it.

Then, there has to be a reasonably simple distinction between what should be sharp and what should be blurred. As soon as you have background objects at different distances, which should have different amounts of blur. it becomes tremendously difficult. Foreground blur is even more difficult. Blur which varies from one part of a subject to another - as opposed to varying only between discrete objects - is the most difficult of all.

One aspect of blur is impossible to fake in a single photograph. A large aperture lens "sees around" the edges of out-of-focus objects, incorporating things into the blur which would be occluded if the object was in focus.

So in general the answer is you can't do it, or when you can it will usually take a lot of work and a lot of skill to produce a fairly unsatisfactory result.
 
Steve Balcombe said:
In certain very simple cases you can do it. The subject must be easy to isolate - with a reasonably simple outline. Hair? Forget it.
Click to expand...
Such as:


Steve Balcombe said:
Then, there has to be a reasonably simple distinction between what should be sharp and what should be blurred. As soon as you have background objects at different distances, which should have different amounts of blur. it becomes tremendously difficult. Foreground blur is even more difficult. Blur which varies from one part of a subject to another - as opposed to varying only between discrete objects - is the most difficult of all.
Click to expand...
Such as:


Steve Balcombe said:
One aspect of blur is impossible to fake in a single photograph. A large aperture lens "sees around" the edges of out-of-focus objects, incorporating things into the blur which would be occluded if the object was in focus.
Click to expand...
Such as (there was a wire mesh between us - it was at the zoo):


Steve Balcombe said:
So in general the answer is you can't do it, or when you can it will usually take a lot of work and a lot of skill to produce a fairly unsatisfactory result.
Click to expand...
Right. Look at it this way. If it takes you half an hour to do an image (and it will, easily) if you need to do one image and you save $400, that's $800 an hour! Great! If you have to do 100 images, it's $8 an hour. 1000? $0.80 an hour. And those are some painful, frustrating hours, let me tell you.

--
Lee Jay
(see profile for equipment)
 
alexandre_k said:
Bezbozny said:
[…] i would like to ask if there is a difference in obtaining the same effect with a little post processing in photoshop. […]
Click to expand...
ok, but then you're "photoshoping" and not "photographing", no?

food for thought, i'd say!
Click to expand...
whatever keeps us happy. there is nothing odd about "photoshoping" and it is a skill in itself just like "photographing" ... food for thought :)

As for OPs question, my own assessment is doing it in PS is a very hard way to achieve the same (if you attain the skill to achieve it consistently). So the assumption about little post processing may be an oversimplification. It may be good enough to spend the time and effort to get a handful of images processed and prove the point that it can be done, but when people start taking pictures on a regular basis, they quickly find out that the right tool can do it more quickly for them

Now, DOF is only half the story when talking about fast lenses. To me, the more important factors are ability to get better shutter speeds in lower light and the possibility of better AF (since AF works on wide open aperture)

--
PicPocket
http://photography.ashish-pragya.com

 
Sometimes you can sort of fake narrow DOF in post, depending upon the photo, by selectively blurring areas of the photo -- but this is a poor substitute for doing the blur in the camera in virtually every case.

Dan
Bezbozny said:
I hear about many people buying very expensive lenses in order to produce a shallow DOF in the portraits and i would like to ask if there is a difference in obtaining the same effect with a little post processing in photoshop. I am thinking of buying the sigma 50mm 1.4 for my canon 40D buy i am thinking if at the end the result will be the same and i will be throwing money for no reason. I am not a pro so i dont make money from my pics and i am not rich either to buy expensive glass easily.

Another thing that i would like to add is that with a smaller aperture you get sharper image and by postprocessing the background you get both a very sharp image and a shallow DOF, while from what i read many lenses are not very sharp when they are wide open.

I know that the real thing is always bettr than faking it...but at the end of the day...is there a really huge difference?

Thank you in advance,

Bezbozny.
Click to expand...
--
---
G Dan Mitchell - SF Bay Area, California, USA
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Gear List: Cup, spoon, chewing gum, old shoe laces, spare change, eyeballs, bag of nuts.
 
Thank you very much for your answers which were very interesting and informative. The truth is that i have recently bought the canon 50mm 1.8, but unfortunately i don't use it because i found something like a crack in one internal lens component (not in the front or back element). I currently can not replace it since i will be back to the shop that i bought it in 3 months. i am afraid to use it because it might spoil some pics. So in 3 months that i will change it i was thinking if it would be wise to invest in a better lens like the sigma 50mm 1.4 instead having the current one replaced for the same lens.

Oh and some pics of the problem in case that you have a better insight than me. The lens is brand new and has never been used (yes i know.. i should check it at the store before buying it...)

http://www.flickr.com/photos/40510676@N03/3727990603/
http://www.flickr.com/photos/40510676@N03/3727990493/
http://www.flickr.com/photos/40510676@N03/3727990435/
http://www.flickr.com/photos/40510676@N03/3727990347/
http://www.flickr.com/photos/40510676@N03/3727990245/
 
Bezbozny said:
i don't use it because i found something like a crack in one internal lens component (not in the front or back element).
Click to expand...
sure it's not a dust spec or something rather than a crack? Anyway, here is an interesting take on it: http://forums.dpreview.com/forums/read.asp?forum=1029&message=32371488
Bezbozny said:
I currently can not replace it since i will be back to the shop that i bought it in 3 months.
Click to expand...
Hmmm... so will they replace it after 3 months? If yes, then you should wait
Bezbozny said:
i am afraid to use it because it might spoil some pics.
Click to expand...
try to take some pictures and see if you can spot anything ;-)
Bezbozny said:
So in 3 months that i will change it i was thinking if it would be wise to invest in a better lens like the sigma 50mm 1.4 instead having the current one replaced for the same lens.
Click to expand...
I would be happy if shops here let me use a lens for 3 months and then upgrade. Better than saving for next lens or renting out

--
PicPocket
http://photography.ashish-pragya.com

 
I called them and they told me that they will replace it. I explained to them that i am abroad at the moment and can not go to the shop.
 
Bezbozny said:
I am thinking of buying the sigma 50mm 1.4 for my canon 40D buy i am thinking if at the end the result will be the same and i will be throwing money for no reason.
Click to expand...
You have to decide for yourself: how much time is your lens worth? I take about 100~200 pictures in a standard outting... PP each one for shallow DOF, at 10 minutes per (???), it would take more than 24 hours extra PP to work through.

--
-CW

よしよし、今日も生きのいい魂が手に入ったな
 
It is just a piece of dust inside the lens. Quite normal, it happens even with much more expensiv lenses. It should not be a problem at all. You will not see this partical in the image.

Cheers

Richard
 
Thank you for your reply. I am not so sure that it is a piece of dust, but even if it is it is a huge one! I have lenses that have a lot of dust inside and it does not look like this...
 
just when I wanted to select some samples from my archive I saw your post. Nothing to add. This can not be done (in reasonable time anyway) in photoshop. Not by me anyway, maybe by some highly skilled, and therefore expensive, photoshop pro.

Rob
--
'Life is funny but not Ha Ha funny. Peculiar I guess'. (Mr. E.)
 
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