Digital 101---Depth of Field

Jarrell Conley · May 20, 2002

And you did a fine job of lassoing, Iso.

ISOMatrix said:
Here is hopefully another example of breaking the rules. Though
there is nothing special with these images, I hope they do
illustrate MDTrouts point of using digital processing techniques to
break the boundaries of Depth of Field physics.

Here is the original image shot at f5 1/241 7.7mm. Although I had
enough available shutter to have opened up the aperture for more
shallow a depth of field........I didn't...lol.

--------------------------------------------------------------------------------------------------
The following image has less depth of field and hopefully draws
attention to the glove a bit more. I did this digitally in
photoshop.

The reduced depth of field was done using a gaussian blur. I first
duplicated the original layer (making sure it was the top layer.) I
then selected the glove w/ the Magnetic Lasso, then inverted the
selection so that everything EXCEPT the glove was selected.

I DID NOT APPLY A GAUSSIAN BLUR AT THIS POINT HOWEVER! I then
created a layer mask and used a linear gradient to make a gradual
fade so that the top layer faded from the fence to close to the
glove (100% to 0% opacity). Only then did I try various amounts of
gaussian blur. By doing this I had hoped to create a natural
blurring effect that was most severe at the distant objects of the
photo and fading to no blur at the central subject (glove). I then
tried to finish things off by manually using the blur tool to try
to eliminate the "hard edge" of the blurred/non-blurred border.

Although clearly I could've done a better job w/ the faded blur
effect, at least I hope it helps to illustrate a possible technique
to achieve more natural looking Digital Depth of Field adjustments.

-cp5000, om2n

--
Jarrell Conley

MDTROUT · May 20, 2002

What I'm trying avoid is to much terminology and confusing the issue by going too deep. I wanted to stay with the very basic's and let those who want further info to explore on their own. I believe that going into areas such as circle of confusion will do just that create a circle of confusion. Lets keep it simple. We could discuss things like the angle of reflection is equal to the angle of incidence but saying if you point a light straight into a mirror it refects straight back is simple.

You are right about the angle sorry for the foofoo. That is the reason Canon calls three of their lenses tilt and shift because you can tilt the lense and shift the axis or angle of focus thus creating the effect of increasing depth of field.

I use a Nikon 995, this forum, know people in here and thought I would try it among friends first. All instructional documents are typed in word and I copy them into the forum so I have the files and can edit them for content.

Thanks for your interest.

Troutman

CLTHRS said:
I did not mean to imply thet you haven't used or understand large
format techniques.

But if this is intended to be a "101" class you need to get the
basics correct. Saying that tilting the lens increases the
depth-of-field is not correct. If you had written something along
the lines of "cheating" or "fooling" the depth of field, then I
would not have felt compelled to ellaborate.

We are all aware how carefully we need to word statements of fact
in these forum.

I was also surprised to find no mention of the "circle of
confusion". It is a very important basic concept that is part of
understanding depth of field.

I salute your efforts in this ongoing project.

I do have one question. Why did you choose the Nikon Forum for this
series of posts? Are you trying to limit it's participants to a
workable number? Otherwise I would consider the "Open Talk" forum,
where more people could learn from your method.

MDTROUT · May 20, 2002

I understand cameras but this photoshop thing has me pulling my hair out.

I understand what can be done but trying to do it is hard. we did to have a forum on working with ps and ps le to learn simple procedures for using each tool.

Thanks for the post.

troutman

ISOMatrix said:
Here is hopefully another example of breaking the rules. Though
there is nothing special with these images, I hope they do
illustrate MDTrouts point of using digital processing techniques to
break the boundaries of Depth of Field physics.

Here is the original image shot at f5 1/241 7.7mm. Although I had
enough available shutter to have opened up the aperture for more
shallow a depth of field........I didn't...lol.

--------------------------------------------------------------------------------------------------
The following image has less depth of field and hopefully draws
attention to the glove a bit more. I did this digitally in
photoshop.

The reduced depth of field was done using a gaussian blur. I first
duplicated the original layer (making sure it was the top layer.) I
then selected the glove w/ the Magnetic Lasso, then inverted the
selection so that everything EXCEPT the glove was selected.

I DID NOT APPLY A GAUSSIAN BLUR AT THIS POINT HOWEVER! I then
created a layer mask and used a linear gradient to make a gradual
fade so that the top layer faded from the fence to close to the
glove (100% to 0% opacity). Only then did I try various amounts of
gaussian blur. By doing this I had hoped to create a natural
blurring effect that was most severe at the distant objects of the
photo and fading to no blur at the central subject (glove). I then
tried to finish things off by manually using the blur tool to try
to eliminate the "hard edge" of the blurred/non-blurred border.

Although clearly I could've done a better job w/ the faded blur
effect, at least I hope it helps to illustrate a possible technique
to achieve more natural looking Digital Depth of Field adjustments.

-cp5000, om2n

Sasha Obad · May 21, 2002

something I would like to accomplish more often is attaining shallower dof with my 995 & sb-28 at night or dimly lit indoors while keeping the b/g well exposed. The only way I have been able to get this to work is by using my 2x teleconverter. Works great when I've got lots of room to back up from the subject - but indoors I have to rely on PS to blur the b/g.

Icarusfree · May 21, 2002

ISO:

thanks for the faded layer tip!! I have tried this so many times at photoshop just to get frustrated witha non-natural looking picture. I guess that more PS learning time is required ... however I first will try to understand beeter my camera and the basic concepts of photography!

Keep posting friends!! Your advice and suggestions are great for newbies like myself!

ISOMatrix said:
Here is hopefully another example of breaking the rules. Though
there is nothing special with these images, I hope they do
illustrate MDTrouts point of using digital processing techniques to
break the boundaries of Depth of Field physics.

Here is the original image shot at f5 1/241 7.7mm. Although I had
enough available shutter to have opened up the aperture for more
shallow a depth of field........I didn't...lol.

--------------------------------------------------------------------------------------------------
The following image has less depth of field and hopefully draws
attention to the glove a bit more. I did this digitally in
photoshop.

The reduced depth of field was done using a gaussian blur. I first
duplicated the original layer (making sure it was the top layer.) I
then selected the glove w/ the Magnetic Lasso, then inverted the
selection so that everything EXCEPT the glove was selected.

I DID NOT APPLY A GAUSSIAN BLUR AT THIS POINT HOWEVER! I then
created a layer mask and used a linear gradient to make a gradual
fade so that the top layer faded from the fence to close to the
glove (100% to 0% opacity). Only then did I try various amounts of
gaussian blur. By doing this I had hoped to create a natural
blurring effect that was most severe at the distant objects of the
photo and fading to no blur at the central subject (glove). I then
tried to finish things off by manually using the blur tool to try
to eliminate the "hard edge" of the blurred/non-blurred border.

Although clearly I could've done a better job w/ the faded blur
effect, at least I hope it helps to illustrate a possible technique
to achieve more natural looking Digital Depth of Field adjustments.

-cp5000, om2n

Sasha Obad · May 21, 2002

ISOMatrix said:
I DID NOT APPLY A GAUSSIAN BLUR AT THIS POINT HOWEVER! I then
created a layer mask and used a linear gradient to make a gradual
fade so that the top layer faded from the fence to close to the
glove (100% to 0% opacity). Only then did I try various amounts of
gaussian blur. By doing this I had hoped to create a natural
blurring effect that was most severe at the distant objects of the
photo and fading to no blur at the central subject (glove). I then
tried to finish things off by manually using the blur tool to try
to eliminate the "hard edge" of the blurred/non-blurred border.

Thanx for the excellent tips! Unfortunately, I got lost after the part where you made the linear gradient :-(

After I apply the gaussian blur to the gradiant layer, i can't see it because I guess it's under the layer mask? how to I show it?

here is a screen shot of what I have so far...and THANX again!

--
Sasha Obad
Coolpix 995
gallery: http://www.canucks.ca

ISOMatrix · May 21, 2002

Sasha Obad said:
Sasha Obad said:

I DID NOT APPLY A GAUSSIAN BLUR AT THIS POINT HOWEVER! I then
created a layer mask and used a linear gradient to make a gradual
fade so that the top layer faded from the fence to close to the
glove (100% to 0% opacity). Only then did I try various amounts of
gaussian blur. By doing this I had hoped to create a natural
blurring effect that was most severe at the distant objects of the
photo and fading to no blur at the central subject (glove). I then
tried to finish things off by manually using the blur tool to try
to eliminate the "hard edge" of the blurred/non-blurred border.

Click to expand...

Thanx for the excellent tips! Unfortunately, I got lost after the
part where you made the linear gradient :-(

After I apply the gaussian blur to the gradiant layer, i can't see
it because I guess it's under the layer mask? how to I show it?

here is a screen shot of what I have so far...and THANX again!

--
Sasha Obad
Coolpix 995
gallery: http://www.canucks.ca

Sasha, Tho I'm no PS expert...I believe all that you need to do is to use the "background copy" layer as the layer mask layer.

Click on the mask button on the Layer dialog box while "background copy" layer is active. Then apply your linear gradient. If you go back to the normal view (not mask view) of this layer you should see this layer fade from transparent to 100% opaque. Then apply your gaussian blur. Hope this helps!

good luck!
--
CP5000, OM-2n

Joan Corrie · May 21, 2002

You are making me think! I had taken this photo of grandaughter's pet. She wanted me to hold it, and I said I believe I'd just take its picture instead. We both were pleased with the outcome, but when I studied it for dof I see I didn't get the eyes in focus as clearly as her thumb under the lizard's rear foot. Thanks for the effort in helping us improve our work. I won't bore you with a couple other photos I practiced the dof exercise, but it does make a difference. Joan

fti · May 21, 2002

I've been free-riding for the past couple of days. Thanks everyone for your input, I feel like I'm learning with leaps and bounds.

fti

MDTROUT said:
Digital 101 is designed to accomplish one thing and one thing only.
Improve the image quality of anyone who is interested in better
pictures.
It is open anyone and should be a learning expierence and not a
place for critics as I want anyone to be comfortable coming here
for advice.

I run a photo lab and look at thousands of could have been images
every week. Yet the same folks look at my images and say I could
never do that.
Not true, you don't learn to be a doctor overnight and the same is
true with photos, knowing basic fundementals and alot of practice
creates good images.

I had a mother come in today and left with tears in her eyes as her
photos of her sons graduation did not turn out as she didn't
understand how a flash works and all she got the the reflection of
the guys bald head in front of her. If I can do nothing more then
help some other person avoid such disappointment them I will be
happy.

I plan on posting a subject every week that we can discuss, post
example photos, and by the end of the week give as many folks
possible basic info on how to improve their technique. If you
submit a photo post please explain how you achieved the image and
why.

So lets get started. Some of this stuff may be basic for some and a
revelation for others. All ideas appreciated.

This weeks subject is depth of field. Depth of field is simply the
area in focus on any photo. There are many reasons to expand or
reduce the area in focus. Landscapes of scenery require focus from
three feet to infinity yet in many portraits you want the
background out of focus so as not to detract from the person who is
the center of attention.

Yet in other areas you may want both alot or little depth of field.
One such area is in macro photos. Sometimes with extreme macro you
need alot of dof just to get the main subject in focus but if you
are shooting say the pollen on a part of the flower you may want to
blur the background to place emphasis on just themain item in the
photo.

You can control dof with your aperature priority setting on your
camera.
Simply dof is greater at f22 then at f2. Th try this find a fence
or anything that goes away from you at an angle. Set your camera at
f2 and take a picture. Then from the same position take another
picture this time at the highest aperature setting on your camera
say f11 and look at both images and you will see the one at f11 has
more area in sharp focus then the pic at f2. You have jsut learned
to control dof. The next goal is to leran when to control dof.
Thats what we can learn from this weeks discussion and photo posts.

I photo I will post is of a waterfall which is thirty feet from
where the water is flowing over the rocks in the front of the
image. This one example of maximizing dof. I will post several
other pics during the week that so different perspective and use
of dof.

Lets make this work and have fun with it.

troutman

MDTROUT · May 21, 2002

Just watched Canon Photo Safari and as someone early in this discussion mentioned that dof was effected by the type of lense used. Low and behold the professional mentioned how lense type had a great deal to do dof.

Jarrell posted a picture of a padlock and mentioned how dof was effected by how close you are to the subject. His point was that close-up you have less dof to work with than with scenics or landscapes.

The opposite holds true with lenses in that the smaller the mm of the lense the easy to control depth of field. Her point was that she visualized a picture in layers. For instance if you have a scene in Africa of a river in the foreground with an alligator on the far bank and an elephant beyond that with mountains in the background that she see's all these different elements as separate layers. So her decision is how many of these layers does she want in the picture and how many in focus.

If she wants them all in focus a wider angle lense will give her a greater chanceof achieving her goal. If she just wants the river and gator a medium to moderate telephoto may be the best choice because it compresses distance and makes it easier to blur the background and may eliminate some of the background layers all together.

Just another way to work with dof.

troutman

MDTROUT said:
Digital 101 is designed to accomplish one thing and one thing only.
Improve the image quality of anyone who is interested in better
pictures.
It is open anyone and should be a learning expierence and not a
place for critics as I want anyone to be comfortable coming here
for advice.

I run a photo lab and look at thousands of could have been images
every week. Yet the same folks look at my images and say I could
never do that.
Not true, you don't learn to be a doctor overnight and the same is
true with photos, knowing basic fundementals and alot of practice
creates good images.

I had a mother come in today and left with tears in her eyes as her
photos of her sons graduation did not turn out as she didn't
understand how a flash works and all she got the the reflection of
the guys bald head in front of her. If I can do nothing more then
help some other person avoid such disappointment them I will be
happy.

I plan on posting a subject every week that we can discuss, post
example photos, and by the end of the week give as many folks
possible basic info on how to improve their technique. If you
submit a photo post please explain how you achieved the image and
why.

So lets get started. Some of this stuff may be basic for some and a
revelation for others. All ideas appreciated.

This weeks subject is depth of field. Depth of field is simply the
area in focus on any photo. There are many reasons to expand or
reduce the area in focus. Landscapes of scenery require focus from
three feet to infinity yet in many portraits you want the
background out of focus so as not to detract from the person who is
the center of attention.

Yet in other areas you may want both alot or little depth of field.
One such area is in macro photos. Sometimes with extreme macro you
need alot of dof just to get the main subject in focus but if you
are shooting say the pollen on a part of the flower you may want to
blur the background to place emphasis on just themain item in the
photo.

You can control dof with your aperature priority setting on your
camera.
Simply dof is greater at f22 then at f2. Th try this find a fence
or anything that goes away from you at an angle. Set your camera at
f2 and take a picture. Then from the same position take another
picture this time at the highest aperature setting on your camera
say f11 and look at both images and you will see the one at f11 has
more area in sharp focus then the pic at f2. You have jsut learned
to control dof. The next goal is to leran when to control dof.
Thats what we can learn from this weeks discussion and photo posts.

I photo I will post is of a waterfall which is thirty feet from
where the water is flowing over the rocks in the front of the
image. This one example of maximizing dof. I will post several
other pics during the week that so different perspective and use
of dof.

Lets make this work and have fun with it.

troutman

Jarrell Conley · May 22, 2002

Joan, you mention not getting the lizard eyes in focus as clearly as other parts. With the type cameras we use, it can be very difficult sometimes to focus on the exact spot we want. That's a problem because in being able to do so we can better control the pictures depth of field. I guess you can blame it on auto focus. The camera tries it's very best to lock onto what it "thinks" is important and unfortunately that may be something in front of or behind your main subject..... thus the depth off field may not include something you wanted to be tack sharp, like the lizards eyes.

It sounds like I'm knocking Auto focus but actually most of the time I like it. I just wish I always knew the exact spot the camera focused on. I know that spot can be determined sometimes but in the real world it can be difficult.
Jarrell

Joan Corrie said:
You are making me think! I had taken this photo of grandaughter's
pet. She wanted me to hold it, and I said I believe I'd just take
its picture instead. We both were pleased with the outcome, but
when I studied it for dof I see I didn't get the eyes in focus as
clearly as her thumb under the lizard's rear foot. Thanks for the
effort in helping us improve our work. I won't bore you with a
couple other photos I practiced the dof exercise, but it does make
a difference. Joan

--
Jarrell Conley

Baywing · May 22, 2002

In Manual you can select the spot area focus and brackets appear on the LCD. Using the toggle, you can select which zone you want to use. The biggest advantage is that this turns off the camera's automatic selection mode which will always choose the closest object to focus on. I was getting very frustrated last year with inadequate depth of focus because of this. I turned off the auto feature and now select my area. Even at that, there are times I want to focus on something outside of where the brackets are, so I just put the designated bracket on the subject, 1/2 press the shutter, when the focus locks, I recompose and shoot. Works every time!

Jarrell Conley said:
Joan Corrie said:

You are making me think! I had taken this photo of grandaughter's
pet. She wanted me to hold it, and I said I believe I'd just take
its picture instead. We both were pleased with the outcome, but
when I studied it for dof I see I didn't get the eyes in focus as
clearly as her thumb under the lizard's rear foot. Thanks for the
effort in helping us improve our work. I won't bore you with a
couple other photos I practiced the dof exercise, but it does make
a difference. Joan

Click to expand...

--
Jarrell Conley

Phil Dunne · May 22, 2002

ISOMatrix said:
Sasha, Tho I'm no PS expert...I believe all that you need to do is
to use the "background copy" layer as the layer mask layer.

Click on the mask button on the Layer dialog box while "background
copy" layer is active. Then apply your linear gradient. If you go
back to the normal view (not mask view) of this layer you should
see this layer fade from transparent to 100% opaque. Then apply
your gaussian blur. Hope this helps!

good luck!
--
CP5000, OM-2n

ISO:

Good tip. I prefer not to use PS if I can to cover up the fact I'm a terrible photographer - but I must. I might clarify the steps in my own words?

1. Use the lasso or magnetic lasso tool to select the glove. Hint: There is also a straight edge lasso for selecting things like buildings. Go up to Select -> Feather and use a pixel radius of 2 to soften the edges a little. Now hold Ctrl - C to copy the image and then paste it to a new layer.

2. Select the original layer in the layers pallete. Press Q on the keyboard to enter Quickmask mode. If you use the paint brush here or fill/gradient you will see it comes out a pink colour. This pink colour represents the masking 'tape'. Dark pink represents anything not selected, light pink is partially selected and clear is fully selected.

3. Use the gradient tool to mask the area from about 1/2 the way up the glove to the top of the picture. The bottom should be dark pink and the top clear.

4. Hit Q again - you should see the top 1/4 of the image is selected. Go up to filter -> Blur -> Gausian Blur and enter a number. Now see the result. Tidy up any edges on the glove layer until you are happy.

How does this work? The gradient used to gradually mask some areas more than others also means that a filter will work on some areas more than others giving any increasing blur the more selcted it is. You can use radial blur and motion blur for some very interesting effects including the illusion of motion. Also try selecting different areas and applying blur individually to get the best result (eg the fence in the background)

--
Cheers
Phil

cp5000

Jarrell Conley · May 22, 2002

Bay, thanks for reminding me of that feature. I remember several conversations this was mentioned. Now I have something to go out and practice with today. I know I'm going to catch the devil for this..... but, I hate using the lcd to compose. I know, I know... it's by far the most accurate because what you see is what you get, and you have access to features that are not visible in the viewfinder. I'm just going to have to bite the bullet and do and practice with it if I want to KNOW what's in focus.
Jarrell

Baywing said:
Jarrell Conley said:

Joan Corrie said:

You are making me think! I had taken this photo of grandaughter's
pet. She wanted me to hold it, and I said I believe I'd just take
its picture instead. We both were pleased with the outcome, but
when I studied it for dof I see I didn't get the eyes in focus as
clearly as her thumb under the lizard's rear foot. Thanks for the
effort in helping us improve our work. I won't bore you with a
couple other photos I practiced the dof exercise, but it does make
a difference. Joan

Click to expand...

--
Jarrell Conley

Click to expand...

--
Jarrell Conley

Phil Dunne · May 22, 2002

It's a different take on the post-production DOF idea but shows the dramatic effect you can acheive in a few minutes. Here I used a radial gradient instead (after step 1) and used a radial blur (zoom setting) to give the effect of manually zooming in on the flower during a long exposure - about 3mins work all up.

Cheers
Phil

cp5000

Gerald Poirier · May 22, 2002

I like to use the 'off' option of the autofocus area. Then, only the center area is used to autofocus, and I find this predictable and fast to use when I want to pre-focus on a subject then recompose the image.

Gerald

Baywing said:
In Manual you can select the spot area focus and brackets appear on
the LCD. Using the toggle, you can select which zone you want to
use. The biggest advantage is that this turns off the camera's
automatic selection mode which will always choose the closest
object to focus on. I was getting very frustrated last year with
inadequate depth of focus because of this. I turned off the auto
feature and now select my area. Even at that, there are times I
want to focus on something outside of where the brackets are, so I
just put the designated bracket on the subject, 1/2 press the
shutter, when the focus locks, I recompose and shoot. Works every
time!

Joan Corrie · May 22, 2002

Your responses are interesting and helpful, as always. Joan

Joan Corrie said:
You are making me think! I had taken this photo of grandaughter's
pet. She wanted me to hold it, and I said I believe I'd just take
its picture instead. We both were pleased with the outcome, but
when I studied it for dof I see I didn't get the eyes in focus as
clearly as her thumb under the lizard's rear foot. Thanks for the
effort in helping us improve our work. I won't bore you with a
couple other photos I practiced the dof exercise, but it does make
a difference. Joan

Bern Caughey · May 22, 2002

Baywing said:
inadequate depth of focus because of this.

Quoted from ASC's American Cinamatographer Manual.

"The depth of focus should be clearly distinguished from...depth of field. The depth of focus is an infinitely small range behind the lens at the the focal plane within which the film is positioned during exposure. This is most critical, particulary with short-focus lenses. If the film moves out of this precise position,..., it will cause unsharp images..."

"Depth of Focus = (focal length x f-stop) / 1000"

Sasha Obad · May 31, 2002

Filski.

didn't get a chance to thank you for the following excellent lesson!

thanx

sash

Filski said:
ISO:
Good tip. I prefer not to use PS if I can to cover up the fact I'm
a terrible photographer - but I must. I might clarify the steps in
my own words?
1. Use the lasso or magnetic lasso tool to select the glove. Hint:
There is also a straight edge lasso for selecting things like
buildings. Go up to Select -> Feather and use a pixel radius of 2
to soften the edges a little. Now hold Ctrl - C to copy the image
and then paste it to a new layer.

2. Select the original layer in the layers pallete. Press Q on the
keyboard to enter Quickmask mode. If you use the paint brush here
or fill/gradient you will see it comes out a pink colour. This pink
colour represents the masking 'tape'. Dark pink represents anything
not selected, light pink is partially selected and clear is fully
selected.

3. Use the gradient tool to mask the area from about 1/2 the way up
the glove to the top of the picture. The bottom should be dark pink
and the top clear.

4. Hit Q again - you should see the top 1/4 of the image is
selected. Go up to filter -> Blur -> Gausian Blur and enter a
number. Now see the result. Tidy up any edges on the glove layer
until you are happy.

How does this work? The gradient used to gradually mask some areas
more than others also means that a filter will work on some areas
more than others giving any increasing blur the more selcted it is.
You can use radial blur and motion blur for some very interesting
effects including the illusion of motion. Also try selecting
different areas and applying blur individually to get the best
result (eg the fence in the background)

--
Cheers
Phil

cp5000

--
Sasha Obad
New Westminster, BC CANADA
Photo Gallery: http://www.canucks.ca

Sasha Obad · May 31, 2002

btw - i used that lesson on this pic:

--
Sasha Obad
New Westminster, BC CANADA
Photo Gallery: http://www.canucks.ca

Digital 101---Depth of Field

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