Digital Photography 202: Close Up, Macro & Micro

By far the most common subject of photography are humans. But there are occasions when you want a photograph of something much smaller. Since most cameras are designed for taking photos of people they are not capable of close up photography. How close you can get depends on the camera design mainly in terms of what accessories it can utilize.

My motivation is to be able to take photos of insects and other things that are in the 1/4" size range and use focus stacking to make the final images.

Film and digital cameras share a common need and that's to have the subject come close to filling the frame. Because of limited resolution ( grain in flim, pixels in a digiral camera) there will be more detail when the subject comes close to filling the frame. If for example you take a photograph of a fly and it's less than one tenth the length of the imaging device and one tenth of the height of the imaging device then you have only used a hundredth of the avaliable pixels. It's like changing a 10 M Pixel camera into a 1 MPixel camera and that's much too large a hit on image quality. So for these small things some from of optical magnification is needed.

Macro Photography (Wiki) typically relates to magnifications near 1:1 subject:image size. When these images are printed the print is many times larger than the subject.
A photograph taken through a microscope is called a Micrograph (Wiki). Below I'm only addressing conventional light microscope imaging, but there are many sophisticated ways of taking a photograph with various specialized microscopes that involve things like phase contrast, using one color of light to illuminate the subject but taking the photograph at a different wavelength (think CSI), or using electrons instead of light, etc.

When stacking images it's important that the pixels can be aligned. It's my understanding that the automatic image alignment feature works by using translation (X & Y movements) as well as rotation to align the images to be stacked. It does not include changing the magnification of the image. That's why the camera needs to be in manual focus mode and the focus should not be changed since that changes the magnification. In a similar way the aperture (f/number) should not be changed. Since it's desirable that the exposure be the same for all shots in a stack the shutter speed should not be changed.

Optics

Reversed Lens

Reverse Lens Adapter Ring

The idea is to mount a lens so it's turned end for end. This requires a Macro Reverse Adapter Ring. Note you need to specify the camera body lens mount (Nikon F) and the filter thread size of the lens (52mm for one ring and 62mm for another ring). These are typically a few dollars each.

Magic eBay Search Phrase: Nikon F reverse 52mm

A couple of things happen when this is done. First, most modern camera lenses are designed with the idea that you are going to be taking a photo of some human scale subject and focusing that image on a small (about an inch) image sensor. So when you reverse the lens and are taking a photo of something that's smaller than the imaging chip the lens will work in a way that's closer to it's design size ratio. Second, multi-elements lenses typically do not have their center of focus at the mechanical front to back center. So when reversing the lens the subject focusing range will be very different than it was with the lens mounted in the normal way.

By using extension tubes that have male and female threads on each end that match the lens filter threads the reversed lens can be moved away from the camera body. This shortens the subject focus distance, i.e. increases the magnification.

Another way to move the lens further away from the camera body is to use a bellows.

Note that the lens that's reversed does not need to be one that would fit your camera body. It can be any lens that can be mounted. For example by using a series of adapters you could use a movie camera/TV camera C-mount lens (reversed).

Nikon-F to 52 mm Reverse Adapter

Close-Up
Photography using Reversed Lens Nikon-F - 52mm
Filter Thread

Reversed Nikon 105 mm Lens Example

Notice that the hole in the adapter ring is smaller in diameter than the lens.

Close-Up Photography using Reversed Lens Nikon-F - 52mm Filter Thread
The front of the lens (shown above) has the adapter screwed onto it's 52mm
filter threads. The Nikon-F bayonet mates to the camera body.
Note the hole in the adapter is smaller than the front lens diameter, so
there's some light loss.

52mm threads on top and Nikon-F male on bottom

Nikon D300s -
Lens Reversing Ring 62mm - Nikon 35-70mm Lens

Niikon D300s cameera, Lens Reverse adapter Ring 62mm, Nikon 35-70mm Lens, SB-900 flash

Close Up Setup: Nikon D300s, Lens Reversing Adapter 62mm, 35-70mm Lens, Focus Rack, Tiltal Tripod, SB-900 flash

Non cropped (all of the DX frame) Close Up of Dime, Nikon D300s, Lens Reverse Adapter Ring 62mm, Nikon 35-70 Lens

A Dime is about 18mm in diameter
the DX chip is 23.6 mm wide
So the magnification is more than 1:1, maybe 2X.

Nikon 55 mm f/2.8 AiS Marro Lens Example

Note this lens has two magnification scales one for the lens by itself and one when the PK-13 is used.
Note the magnification is the same fro a full frame or half frame camera.
It does matter when calculating the magnification because you need to know the image size.

Note the focusing barrel on this lens moves the complete lens assembly, that's to say it acts like extension rings. So when the lens is reversed there is no change when the focus ring is moved. Except it acts like a variable length lens shade.

Nikon 55 mm AiS f/2.8 Macro Lens

Taken with Nikon 55 mm AiS f/2.8 Macro Lens fully extended and mounted reversed

about 1.07" (21.18mm) showing on 23.6 mm chip or 1.1X magnification
when lens used reversed. This is may just be the extension
caused by the reverse adapter ring.

Notice front scale is in inches and rear scale is mm (1" opposite 25.4mm)

55 mm with MC7 2X Teleconverter

Normal Lens Configuration

Nikon 55 mm
f/2.8 AiS Marro Lens + MC7 2X Teleconverter

1" (25.4 mm) on scale or about 0.9X magnification

Reversed Lens Configuration

Nikon 55
mm f/2.8 AiS Marro Lens Reversed + MC7 2X
Teleconverter

0.6" (15.24 mm) on scale or about 1.5X mag
Click on this photo and you can see 3D effects in the yellow paint.

PK-13 27.5 mm Extension Ring for the 55mm AiS Macro Lens

This only works when the lens is used in the normal configuration.

Nikon PK-13 27.5
mm Extension Ring for 55 mm F/2.8 AiS Macro Lens

Threre is a coupling between the lens f/stop setting and the camera body and so the camera knows the f/stop setting. The settings on the lens and the camera matches, I was expecting there to be an offset.

Nikon 55 mm
f/2.8 AiS Marro Lens + PK-13 27.5 mm Extension Fully
Extended (4X?)

The image is 0.9" (22.86 mm) wide and the DX frame is 23.6 mm wide so 1X mag.

Nikon Extension Ring Set nominal 65 mm total length

This extension ring set (Made in China) has two defects.
1) the lens release does not work by pressing down, but rather by pulling toward camera unlike all the other Nikon equipment.
2) the female 56.77 mm O.D. threads are not cut far enough along the centerline axis to allow the mating parts to seat on the flanges, instead they are stopping when the threads no longer fit so not ring 1 is jammed into ring 2 and they will not come apart.

Rings	Length
none	15.92
1
1 + 2 (20.61)	37.76 (sb 36.53)

3 (28.13)	44.9 (sb 44.08)

Nikon D3002 (FlexTT5 Wireless Strobe Trigger and E640 Flash control removed and put on D60 to take this shot) + PK-13 + all of Extension Ring Set Normal Lens Position. 84" Umb & White diffuser.

Same as at left except Just the lens is reversed. The extension tubes remain on the camera in the same position.

Nikon
D3002 (FlexTT5 Wireless Strobe Trigger and E640
Flash control removed and put on D60 to take this
shot) + PK-13 + all of Extension Ring Set Reversed
Lens Position.

Taken with 55mm AiS Lens Normal + PK13 + All of Extension Ring Set
55Nikon
mm AiS Lens Reversed + PK13 + All of Extension Ring
Set

About 0.45" (11.4mm) vs. 23.6 mm frame width so
2.0X mag.

Taken with 55mm AiS Lens Reversed + PK13 + All of Extension Ring Set
Niikon
55mm AiS Lens Reversed + PK13 + All of Extension Ring
Set

About 0.39" (9.9mm) or 2.38X

For more about this lens see StackShot below.

Digital Extension Ring Set nominal max 86 mm

Bellows

A bellows allows for a continious range of extension unlike the fixed steps when extension rings are used.

This was on eBay with the title:
Lens Macro Fold Bellow For Nikon D70 D40 D700 D300 D200 by seller foto4easy.
The flange to flange distance when fully extended is 143 mm (5-5/8").
It can be used with the above extension tubes, tele-extender and/or another extension tube.

You can NOT stack two of these bellows together to get more extension. A poor design.
If you know of a Nikon-f type bellows that allows stacking please let me know.
The setup above (full bellows extension, full 55mm lens extension should result in 3.2X mag.

The Nikon Bellows Focusing Attachment II (for F) does NOT fit the D300s camera because of the right grip bump on the camer body.

Set of Adapters

Macro Lens

Most DSLR manufacturers offer some lenses which have the ability to focus on close up subjects. Typically all the way to 1:1. That's to say the image of the subject on the imaging chip is the same as the size of the subject. Although there are macro type lenses with focal lengths near the normal focal length they are not as popular as longer focal lengths. One of the main reasons for this is that with the longer focal lengths the subject ends up being maybe an inch or more in front to the lens glass. But with the shorter focal macro lens the subject may be a tiny fraction of an inch in front of the glass. That's not good because the subject may scratch the glass and because it's hard to get light on a subject without also getting the light into the lens.

The Nikon AF Micro-Nikkor 105mm f/2.8G ED-IF AF-S VR is great for all around shooting and especially for close up photography. But it's not good for things like a fly or other small insect or spider.

Canon MP E Macro lens - 65 mm - F/2.8

This is a reversed lens (see above) that has electrical contacts on the camera end to allow automatic operation of f/stop and other things (maybe focus, maybe magnification?). Nikon has no lens that competes with it. Nov 2011 about $1,000. To use this lens requires a cannon body.

Canon also makes DSLR cameras that do video recording such as the T3, 60D, 7D and 5D MkII.

The EOS 7D is optimized for HD video.
All these cameras support either sRGB or AdobeRGB color space

Body	Res	Output	Video	$eBay Nov 2011
EOS Rebel T3	APS-C 4272 x 2848	RAW + JPEG	na	na
EOS Rebel T3i	APS-C 5184 x 3456	RAW, JPEG 14-bit	1080	335 - 600
EOS 60D	APS-C 5184 x 3456	RAW + JPEG
EOS 7D	APS-C 5,184 x 3,456	JPEG, RAW (14-bit, Canon original), sRAW, mRAW, RAW+JPEG	1080/24 1080/30 1080/25	675 - 1000
EOS 5D MkII	Full Frame 5616 x 3744	JPEG, RAW (14-bit, Canon original), sRAW1, sRAW2, RAW+JPEG	1080	1780 - 2560

Microscope Lens

There are a number of ways to use a microscope lens.

Microscope

One way you can think of this a adding a camera to a microscope. That can be accomplished a number of ways:

Camera Port

Some microscopes have interchangeable eyepiece holders and one of those has a third port where a camera can be mounted. The advantage is that you look through the regular eyepieces to focus and frame the image (including after changing the objective lens) then take the photo with the camera using a separate light path. Careful setup is required to make sure the camera and eyepieces focus at the same place.

Prime Objective

Here the eyepiece is removed from the microscope and the camera (without a lens) is installed on the eyepiece tube. A SLR type camera would allow focusing with enough light, but other types of camera have specialized focusing needs.

Afocal (Wiki) (Eyepiece projection)

The microscope eyepiece is in place and the camera has it's normal lens in place. The camera is focused at infinity. Although this is the most straight forward method from an optical point of view, the mechanical problems of mounting the camera exactly where it needs to be and in such a way that it does not shake makes this method a last resort rather than something you should strive for. For example you can do this with a cell phone camera in a pinch.

No Microscope

The microscope can be completely bypassed by mounting the objective lens directly on the camera by means of adapters. This saves the cost of the microscope. You loose the substage positioning controls of a microscope, although not all microscopes have them. Also the mounting and focus distance problem now is part of the camera's job.

Using something like the StackShot - a motorized rail camera mount that moves the camera and trigers an exposure over and over again

C/CS Mount TV Lens

This is very similar to using a series of adapters to mount a TV (16 mm movie) lens on a digital camera either in a normal configuraion or with the lens reversed. It turns out that as the image sensor area gets smaller the size (and cost) of a lens to cover that area is also smaller. So excellent lenses for 16 mm film (TV cameras) cost less than 35 mm film lenses and they cost less than 120 roll film lenses like used on Hasselbald cameras and these cost less than the lenses used on 4x5 and 8x10 view cameras.

Cone of Light

A thought about the relative merits of using a microscope lens, TV lens, 35mm size camera lens, or larger lens is which would be better. The best in terms of resolution would be the fastest (lowest numerical f/number) diffraction limited lens (few are).

Note: microscope lenses use Numerical Aperture (Wiki: NA) instead of f/number.
(f/number)_working = 1/(2 * N.A.) *[ m / (m-1)]
where:
N.A. is the Numerical Aperture
m is the magnification
for a 4X objective the common N.A. values range between 0.1 and 0.17 or the f/number (ignoring magnification) is f/5 to f/2.9. My guess is that many of them are diffraction limited.

But, they are designed to be used in a microscope tube that's 160mm long and 23.2 mm I.D. so there will be some vignetting.

When a camera lens is used in the reversed position the filter thread to lens mount adapter may have a smaller hole than the lens diameter thus raising the numerical f/number and degrading the resolution. This could be avoided by using an adapter from lens filter thread to a larger diameter tube, then closer to the camera body stepping down so that the cone of light was not effected.

Optical Theory

Choosing f/Stop

See Digital Photography 101: Basics Resolution for a general discussion of resolution.
See Digital Photography 101: Basics Depth of Field - Fepth of Focus for a general discussion.

Single Exposure

When taking a single exposure it's common to stop the lens down to the smallest aperture. Typically macro lenses have a smaller f/stop than a conventional lens, like F32 or smaller. This allows getting a greater depth of focus (Wiki) but there are some disadvantages to doing this. First it takes a lot more light. If incadencent lamps are used there is enough heat associated with the light to cook the subject and it's difficult to physically get the lights where they need to be because the subject in very close to the front of the lens. Second the resolution of the lens is degraded a lot since resolution is directly related the the effective objective diameter, smaller f/stop = poorer resolution.

Focus Stacking - Multiple Exposures

Getting the maximum depth of focus in each image is no longer the prime consideration since it's accomplished by stacking images. Now there's a trade off between the number of images needed in the stack vs. the resolution of each image. For the highest resolution the lens should be set wide open (if the lens is of very high optical quality) or at the "sweet spot f/stop".

Focal Length

See Digital Photography 101: Basics Focal Length for a general discussion.

To get increased magnification requires using some method of extending the lens to camera distance. This needs to be done is a way that is very stable. Note the longer the extension the higher the magnification so it's even more important for longer extensions. If there's any movement or misalignment caused by the extension then the image may be degraded. The longer the focal length of the lens the longer the extension needs to be, so using a lens with a shorter focal length has an advantage.

The distance between the lens and subject for a given magnification will be greater for longer focal length lenses. This has implications in terms of having enough room to light the subject, so longer focal length lenses have an advantage in that respect.

The Canon MP-E macro lens is 65 mm. The two Nikon macro lenses I have (see above 55 mm, 105 mm) are 55 mm and 105 mm.

Magnification

Magnification (Wiki) is the ratio of the image height on the imaging chip in the camera to the subject height. This would be the final magnification if you were using a film camera and made a contact print. But if the print is an enlargement then the final magnification is themagnification times the enlargement radio. For example if the taking magnification is 1:1 (a common limit for a macro lens) taken on a half frame digital camera (like the Nikon D300s or D60) which has a chip size of 18x12 mm and the print size is 8" x 12" (203mm x 305mm) then the final magnification is about 17 X.

M = hi/ho = di/do = FL/(do - FL) = (di - FL)/FL

M: Magnification
hi: Height of Image
ho: Height of Object (subject)
di: Lens to Image distance
do: Lens to Object distance
FL: Focal Length of Lens

Lens Distances

Wiki (Optical Lens - Imaging Properties)

1/FL = 1/do + 1/di

A key point that bears repeating is that when the distance between the lens and the imaging chip is the focal length objects located at infinity will be in focus.
If do is infinity then 1/do is zero so di must = FL.
For example a magnifying glass focusing the Sun into a small spot.

When the lens is twice the focal length in front of the imaging chip subjects that are two focal lengths in front of the lens will be in focus and the magnification will be 1:1.
If do = di then 1/FL = 1/do + 1/d0 = 2/do or do = 2 * FL

As the lens is moved further and further away from the imaging chip the magnification will increase until the lens is one focal length away from the subject at which point the magnification will be infinite.
If do = FL then di is infinity and mag is infinity.
For example a condenser lens in a slide projector is focused on the lamp filament and projects a beam of collimated light

Flange Focal Distance (Wiki)

This Wiki page has a table of the distance between the camera flange and the front surface of the image sensor chip for many cameras.
For the Nikon-F lens mount this distance is 46.5mm.
This number is needed when doing lens related computations.dig

This distance puts a bound on what focal lengths can be used.

Extension Calculations

Using the 55mm AiS lens.

When focused all the way toward infinity the length of the lens from camera flange to front (without any filter or adapter ring) = 62.17mm.
When fully extended the flange to front distance is 95.35mm or an extension of 33.18 mm
The Nikon Flange Focal Distance is 46.5mm.
The Nikon DX chip is 23.6 mm wide (not half a 35mm film frame that I wrongfully thought).

FL = 55mm - 46.5 mm = 8.5mm distance from flange to focal point of lens.
62.17 Lens length - 8.5mm = 53.67 mm distance from front of lens to optical center.=

Case 1 Fully Extended Normal Lens (0.5X nominal)

The "2" on the reproduction scale means 1:2 film:sulject or half size image).

When fully extended di = 55mm + 33.18 mm = 88.18mm
Mag = (di - FL)/FL = (88.18 - 55) / 55 = 0.6X close to the 0.66 measured and near the 0.5X in the specs.

Case 2 Fully Extended Normal Lens + PK -13 (1X nominal)

Now di increases by the PK-13: 88.18 + 27.5 = 115.68mm
Mag = (115.68 -55) / 55 = 1.1X close to the spec of 1X.

Case 3 Fully Extended Normal Lens + PK-13 + 65MM Extension Ring Set (2X nominal)

di = 88.18 + 27.5 + 65 = 180.68
Mag = (180.68 - 55) / 55 = 2.29X Actual is more like 2X

Case 4 Fully Extended Lens (33.18mm) + Fully extended Bellows (143mm)

di = 55 + 33.18 + 143 = 231.18
Mag = (231.18 - 55) / 55 = 3.2

Hardware

The Nikon D300s is a relativity heavy camera when compared to a TV camera and so mounting it to a microscope may not be a good idea. It seems like a better idea to add whatever optics are going to be used directly to the D300s and then mount the D300s to something that can hold it. That might be a tripod, like the Tiltall that can be used with the center column inverted and optionally with the StackShot automated motion stage to allow focus stacking.

Another option may be to build a bench top setup for the StackShot that would include a stage for the subject and provision for strobe lighting.

StackShot

As receivd photo of stack shot, IR remote, Nikon Cable release cord.	Nikon D300s in Mirror Up mode, StackShot Configuration 2 shots/slide stop
Dime 12 shots 750um spacing, Photoshop CS4 stack, D300s, 55mm f/2.8 AiS Rev, StackShot On my monitor (1280x960) the photo at left is 3-3/4" dia (5.4X) When I click on it the new image is 9-3/4" dia (14X) and the cursor is a (+) s0, clicking again makes it 14-3/4" diameter (21X) Light from Einstien E640	Einstien E640 + 22" Spun Aluminum Parabolic Relfector (Retro Laser) light modifier. This single light was used for the photo of the Dime.	Spider - 22 images stacked MC7 + PK13 Reversed 55mm AiS
		Same spider as above, but from other side Wolf spider (Wiki) 8 eyes
Real 2011 U.S. Silver Dollar I was going to use the StackShot to take photos of some coins, but this shot was all in focus because the coin is big enough the high magnification is not needed to see all of it. But taking a close up of some feature might require focus stacking.
Fake1865 & 1875 US Silver Dollars Front	1865 & 1875 US Silver Dollars Back	<- taken hand held with 35-70mm lens & off camera SB-900 storbe using Pocket Wizards. It turns out these are fakes. 1) a magnet will pick them up. 2) they weigh 17 g not 27g

Battery Power

The plastic sheet is to keep out of the dew. The cable from the 257477BA battery adapter would be better if 8 feet long. Bunge cord holding SnapShop Computer to tripod. Need to really know Depth Of Focus, other wise you take way more shots than needed. Should check to be sure camera has fresh battery before starting. Major Problem is no way to switch to portrait mode. Maybe an angle bracket?
Not Stacked Mushroom taken 9:15 am	Not Stacked Mushroom at left taken 10:00 am Notice black area eating up dome.	Different Mushroom after another day or more. Stack

The Stack Shot wall wart power supply is rated 12V <= 2 amps. Positive center contact.
The DC power plug appears to be a common 5.5 x 2.1mm type.
The 10 "D" cell battery adapter with the Power Pole option will power the StackShot or a Cigarette Lighter Plug cable with the correct DC power plug.
The battery from the Vagabond AC Inverter that goes with the E 640 studio strobe will also work as a power source.

Create An Automated Macro Rail For Image Stacking -

StackShot - moves camera, triggers shutter, keeps doing it. Shutter release cables for common cameras. 200mm extended slide.
Computer connection with USB.
Pat App 12/927,166 Motor controlled macro rail for close-up focus-stacking photography

Trinamic PANdrive PD-110-42 available from Semiconductor Store (California) a stepper motor combined with a RS-232 interface and some smarts.

Open-source Photographic Motion Control technology.