Digital Depth of FieldDigital Depth of Field

Presented byPresented by

N. David KingN. David King

Digital Depth of Digital Depth of FieldField

Before we talk about EXTENDING or Before we talk about EXTENDING or altering altering Depth of FieldDepth of Field we need to make we need to make sure we understand what it is and why we sure we understand what it is and why we might want to modify it.might want to modify it.

Depth of FieldDepth of Field is the area from in front of is the area from in front of the main subject or plane of the main subject or plane of critical/maximum sharpness to somewhere critical/maximum sharpness to somewhere behind the subject that behind the subject that APPEARSAPPEARS to be to be focused in the final print or image.focused in the final print or image.

© N. David King

Depth of What???

Digital Depth of FieldDigital Depth of Field

Depth of Field is not real… it is an illusionDepth of Field is not real… it is an illusion This limited field of This limited field of apparentapparent sharpness, the “Depth of Field,” is sharpness, the “Depth of Field,” is

unique to photography and is used extensively to help isolate unique to photography and is used extensively to help isolate subjects.subjects.

© N. David King

Depth of What???

Digital Depth of Digital Depth of FieldField

Depth of Field is not real… it is an illusionDepth of Field is not real… it is an illusion Our human vision links our optical input devices (eyes Our human vision links our optical input devices (eyes

and optic nerves) to our brains to constantly re-focus and optic nerves) to our brains to constantly re-focus as we scan a scene so it all appears to be sharp to us as we scan a scene so it all appears to be sharp to us from foreground to background.from foreground to background.

A camera lens cannot do that. There is only one point A camera lens cannot do that. There is only one point in space where it is actually focused, i.e. rendering in space where it is actually focused, i.e. rendering points of light in the scene as the smallest points of light in the scene as the smallest circles of circles of confusionconfusion it can. it can.

That plane of sharpest focus, measured from the That plane of sharpest focus, measured from the cameras image plane, is called the “Focal Distance.”cameras image plane, is called the “Focal Distance.”

© N. David King

Depth of What???

Digital Depth of Digital Depth of FieldField

Depth of Field is not real… it is an illusionDepth of Field is not real… it is an illusion As objects in space occur closer or farther away from As objects in space occur closer or farther away from

the focal distance, the lens produces larger circles of the focal distance, the lens produces larger circles of confusion from each point of light.confusion from each point of light.

When those circles of confusion reach a size of When those circles of confusion reach a size of approximately 1/200 inch on a print, we will start to approximately 1/200 inch on a print, we will start to see it as being “out of focus.”see it as being “out of focus.”

As objects increase in distance from the point of As objects increase in distance from the point of sharpest focus they become increasingly out of focus sharpest focus they become increasingly out of focus or “soft” and indistinct. It is painful for us to try to or “soft” and indistinct. It is painful for us to try to focus something non-focusable so we look away.focus something non-focusable so we look away.

© N. David King

Depth of What???

Digital Depth of FieldDigital Depth of Field

Depth of Field is not real… it is an illusionDepth of Field is not real… it is an illusion This limited field of This limited field of apparentapparent sharpness, the “Depth of Field,” is sharpness, the “Depth of Field,” is

unique to photography and is used extensively to help isolate unique to photography and is used extensively to help isolate subjects.subjects.

© N. David King

Depth of What???

Digital Depth of FieldDigital Depth of Field

Depth of Field is not real… it is an illusionDepth of Field is not real… it is an illusion Depth of Field is actually a product of magnification but Depth of Field is actually a product of magnification but

photographers use several “controls” for it, most commonly the photographers use several “controls” for it, most commonly the aperture.aperture.

© N. David King

Depth of What???

Digital Depth of FieldDigital Depth of Field

Depth of Field is not real… it is an illusionDepth of Field is not real… it is an illusion The result is extensive control over how much of the scene will The result is extensive control over how much of the scene will

be in focus. be in focus.

© N. David King

Depth of What???

Digital Depth of FieldDigital Depth of Field

Depth of Field is not real… it is an illusionDepth of Field is not real… it is an illusion But there are times when we want a lot of Depth of Field in a But there are times when we want a lot of Depth of Field in a

shot but stopping down the aperture is not a good method to shot but stopping down the aperture is not a good method to obtain it.obtain it.

Why? I’m glad you asked, otherwise I’d not have any excuse for Why? I’m glad you asked, otherwise I’d not have any excuse for this presentation…this presentation…

Every lens has a “sweet Spot.” This is the spot where all of the Every lens has a “sweet Spot.” This is the spot where all of the variables (aperture + focal distance + focal length for a zoom variables (aperture + focal distance + focal length for a zoom lens) are optimized by the designers to achieve the greatest lens) are optimized by the designers to achieve the greatest possible sharpness. possible sharpness.

Opening up or stopping down from that point reduces Opening up or stopping down from that point reduces sharpness.sharpness.

For the aperture part of the equation, with normal rectilinear For the aperture part of the equation, with normal rectilinear lenses that “sweet spot” is commonly (but not exclusively) at lenses that “sweet spot” is commonly (but not exclusively) at about 2-3 stops closed down from wide open. about 2-3 stops closed down from wide open.

© N. David King

Depth of What???

Digital Depth of FieldDigital Depth of Field

Depth of Field is not real… it is an illusionDepth of Field is not real… it is an illusion That means – unfortunately – that the sharpest aperture is not That means – unfortunately – that the sharpest aperture is not

anywhere near the aperture yielding maximum depth of field.anywhere near the aperture yielding maximum depth of field. For example for an For example for an ff2.8 lens, the sweet spot is likely to be 2.8 lens, the sweet spot is likely to be

somewhere around somewhere around ff5.6 to 5.6 to ff8. 8. (BTW…That means that the extra money spent for that fast lens (BTW…That means that the extra money spent for that fast lens

may be working may be working againstagainst you for landscape and macro you for landscape and macro shooting…)shooting…)

Before the digital world arrived on the scene, if you really wanted Before the digital world arrived on the scene, if you really wanted or needed deep depth of field, all you could do was stop down or needed deep depth of field, all you could do was stop down and live with it or in some cases solve it with the optical and live with it or in some cases solve it with the optical movements on a large format view camera using the movements on a large format view camera using the ““Scheimpflug EffectScheimpflug Effect.”.”

© N. David King

Depth of What???

Digital Depth of FieldDigital Depth of Field

Thinking DigitallyThinking Digitally

But working in the digital world we have some new options never But working in the digital world we have some new options never before available because of editing functions such as layering before available because of editing functions such as layering and layer masks.and layer masks.

This concept has existed almost from the first days of photo This concept has existed almost from the first days of photo editors using layers such as PhotoShop.editors using layers such as PhotoShop.

The concept is really simple:The concept is really simple: Take enough shots so that in each shot you have something in Take enough shots so that in each shot you have something in

focus from front to back and in all of them you have everything in focus from front to back and in all of them you have everything in

focus due to overlapping depths of field from shot to shot.focus due to overlapping depths of field from shot to shot.

© N. David King

Extending Depth of Field Digitally

Digital Depth of FieldDigital Depth of Field

Thinking DigitallyThinking Digitally Here is what we are talking about. Here is what we are talking about.

© N. David King

Extending Depth of Field Digitally

Digital Depth of FieldDigital Depth of Field

Doing It… The Shooting PartDoing It… The Shooting Part

There are two main keys to success in shooting for There are two main keys to success in shooting for this outcome…this outcome…

PLANNINGPLANNINGSTEADINESSSTEADINESS

You must think this through before starting or it will You must think this through before starting or it will not come out as you wish.not come out as you wish.

Your camera mount has to be so steady you can Your camera mount has to be so steady you can adjust focus without moving the camera AT ALL.adjust focus without moving the camera AT ALL.

© N. David King

Extending Depth of Field Digitally

Digital Depth of FieldDigital Depth of Field

Doing It… The Shooting PartDoing It… The Shooting Part

Here is an example using a common item you can all Here is an example using a common item you can all relate to… a pair of push pins.relate to… a pair of push pins.

© N. David King

Extending Depth of Field Digitally

These pins were shot with A 180mm f4 Macro lens setAt f11.

You can see that even at f11 only the front tip of the pin is sharp.

Digital Depth of FieldDigital Depth of Field

© N. David King

Digital Depth of FieldDigital Depth of Field

Here is the assembled stack…Here is the assembled stack…

© N. David King

Extending Depth of Field Digitally

Digital Depth of FieldDigital Depth of Field

So How is the Stack of Photos Assembled?So How is the Stack of Photos Assembled?

Manually (for the true masochists out there…)Manually (for the true masochists out there…) With the Aid of SoftwareWith the Aid of Software

Helicon (Helicon (www.heliconsoft.comwww.heliconsoft.com)) PhotoShop CS4 and laterPhotoShop CS4 and later

© N. David King

Extending Depth of Field Digitally

Digital Depth of FieldDigital Depth of Field

So How is the Stack of Photos Assembled?So How is the Stack of Photos Assembled?

The Process In PhotoShopThe Process In PhotoShop1.1. Open Bridge (File > Browse in Bridge)Open Bridge (File > Browse in Bridge)

2.2. In Bridge: Select all ShotsIn Bridge: Select all Shots

3.3. Tools > Photoshop > Load files into Photoshop LayersTools > Photoshop > Load files into Photoshop Layers

4.4. In Photoshop: select all layers to make them all activeIn Photoshop: select all layers to make them all active

5.5. Edit > Auto AlignEdit > Auto Align

6.6. Edit > Auto blend (stack)Edit > Auto blend (stack)

7.7. This will make layer masks and create finalThis will make layer masks and create final

8.8. Flatten layers and congratulate yourself on an impossible shot.Flatten layers and congratulate yourself on an impossible shot.

© N. David King

Extending Depth of Field Digitally

Digital Depth of FieldDigital Depth of Field

T-t-t-t-that’s All there is to it…!!!T-t-t-t-that’s All there is to it…!!!

You can download a copy of this Powerpoint You can download a copy of this Powerpoint presentation and a datasheet on the process presentation and a datasheet on the process in the Photo 204 section on the SDCC page in the Photo 204 section on the SDCC page of my web site:of my web site:

www.ndavidking.com/sdcc.htmwww.ndavidking.com/sdcc.htm

© N. David King

Extending Depth of Field Digitally

Digital Depth of FieldDigital Depth of Field

QUESTIONS?QUESTIONS?

© N. David King

Extending Depth of Field Digitally