On this occasion I wanted to make a test involving relatively long focal length lenses and I have done it through different magnification ranges.

 The good thing about this long focal length lenses is their good working distances ( WD), these lenses are supposed to become part of my field gear but they can also be used in the studio, of course. I forgot to measure their WD but as an example the Rodagon-D 75/4.5 has around 10cm WD at 2X.

The following lenses were tested:

Olympus MC auto 1:1 macro 80mm f4; a good reputation bellows lens, optimized for 1:1 work and a useful working range from 0.5X to 2X.

Rodenstock APO Rodagon-D 1X 75mm f4; a specialized enlarger lens (in fact it is a duplicating lens) optimized for  1:1 work, it's probably use was  film duplication. Its optimum working range goes from 0.7X to 1.5X in 35mm cameras.

Rodenstock APO Rodagon-D 2X 75mm f4.5; other version from same series optimized for 2:1 work, one of its designed tasks may be copying 16mm film to 35mm.

Its optimum working range goes from 1.2X to 2.5X in 6x7 film; as this lens has not got a symmetrical design reciprocal values may apply when reversed so it is also optimized for 0.5X work, having a working range of 0.4 to 0.8X in 6x7 film(It is used at 2X when reversed and at 0.5X when in normal position) I have not found its optimum working range in 35mm cameras but I guess it will have a pretty well balanced behavior from 0.3X to 3X. 

I run several stacking sequences at different magnifications: 0.6X (minimum I could get with Olympus 80mm), 1X, 2X and 2.6X (maximum I could reach with Rodagon-D 75/4); at different apertures like f4 (f4.5 for the Rodagon-D 75/4.5), f5.6 and f8.

The test subjects were a couple of old pc cards; a graphics card and a Ethernet card.

I used office paper around the subjects for light diffusion, light source were three ikea led lamps. Stacks were automatized with stackshot (great help for these repetitive tasks) on a EOS 5D mkII in live view silent mode mounted on a nikon PB-6 bellows.

 The only post processing applied to the pictures was recovery 20 on Camera raw; images were stacked on Zerene stacker Pmax mode.

                                                        0.6X test      FOV 59mm 

In this image you can see in red the crops we will examine later on.

Three stack sequences were run for each lens, clicking on the f number you can see them full size. Next to each of them you can see the number of steps, their size and the exposure time.

All lenses were used in normal position.

Rodagon D 75/4

f4           16 shots with 1mm steps       1/6

f5.6        11 shots with 1.5mm steps    0.3"

f8           8 shots with 2mm steps         0.6"

Rodagon D 75/4.5 Normal

f4.5        14 shots with 1.2mm  steps   1/5

f5.6        11 shots with 1.5mm steps     0.3"

f8           8 shots with 2mm steps          0.6"

Olympus 80/4

f4           16 shots with 1mm steps        1/6

f5.6        11 shots with 1.5mm steps     0.3"

f8           8 shots with 2mm steps          0.6"

Let's have a look to those crops; all three lenses are pretty similar, maybe  the Rodagon-D 75/4 struggles a little more in the corners but it also shows better resolution in the center wide open. The weird thing is that it works better at f4 than at f5.6. 

Thinking about it I realized I made DOF calculations based on 0.5X magnification (I got confused), so probably this is what is wrong.

However I think that there are enough areas completely focused on the full size pictures

Clicking on the image you will see it original size (100% crops)

 1X test       FOV 36mm

Here the full image showing the crop areas, same as before.

On this occasion I did three stacks per lens, but I used the Rodagon-D 75 /4.5 both in normal and reversed position. The reason for that being the Rodagon has an asymmetrical lens design and at 1X is in theory out of its optimum magnification range; I wanted to see which way it works best.

Once again next to the f number you have the number of pictures, step size and exposure time.

Rodagon D 75/4

f4           20 shots with 0.35mm steps  1/13

f5.6        13 shots with 0.55mm steps   1/6

f8            9 shots with 0.80mm steps    0.3"

Rodagon D 75/4.5  Normal

f4.5        17 shots with 0.42mm steps   1/10

f5.6        13 shots with 0.55mm steps   1/6

f8            9 shots with 0.80mm steps    0.3"

Rodagon D 75/4.5 reversed

f4.5        17 shots with 0.42mm steps  1/10

f5.6        13 shots with 0.55mm steps   1/6

f8            9 shots with 0.80mm steps    0.3"

Olympus 80/4

f4           20 shots with 0.35mm steps  1/13

f5.6        13 shots with 0.55mm steps  1/6

f8            9 shots with 0.80mm steps   0.3"

Let's examine those crops; again all three lenses have very good performance. In my opinion the Rodagon-D 2X works better reversed rather than in normal position. Probably the Rodagon-D shows a little more detail in the center of the image but the difference is not as big as I would have expected before running the test. The Olympus also performs very well at this magnification. Do not forget that this is a full frame test; 21mpx seem a lot but pixel density is well below what we find in APS-C cameras.

2X test      FOV 18mm

We get now to the 2X test, here the Olympus is still in is designed working range, The Rodagon-D 2X is in its optimum range (in reversed position) and the Rodagon-D 1X is well outside of its designed working range. I had seen some tests of these Rodagons which suggested the Rodagon-D 1X had better resolution at 2X, this did not make sense to me; how can a lens designed to work at 1X be better than a lens designed for 2X work, specially when both lenses were designed by the same maker. It is true that those tests were always APS-C tests.

 On this stack series I overexposed the shots a little bit, which caused some haloing around the bright white areas; as this is just a test it does not bother me much, as long as we use other areas for the comparison.

Rodagon D 75/4

f4           28 shots with 0.18mm steps  1/6

f5.6        22 shots with 0.25mm steps  0.3"

f8           15 shots with 0.35mm steps  0.6"

Rodagon D 75/4.5 reversed

f4.5        26 shots with 0.2mm   steps    1/5

f5.6        21 shots with 0.25mm steps  0.3"

f8           17 shots with 0.35mm steps  0.6"

Olympus 80/4

f4           26 shots with 0.18mm steps  1/6

f5.6        22 shots with 0.25mm steps  0.3"

f8           15 shots with 0.35mm steps  0.6"

Once we look the crops first thing we can see is that the Rodagon-D 2X is very well optimized for 2X work; it was designed with balance in mind, offering almost same performance wide open than with aperture closed 1 or 2 EV. We can also see that both the Olympus and the Rodagon-D 1X struggle in the corners, specially wide open. The rodagon-D 2X is superior even on borders. However the Rodagon-D 1X does show more resolution in the center of the image, which is the reason it seems to be superior in APS-C tests I have seen before.

 2.6X test      FOV 14mm

Taking the results we saw at 2X we can expect them to be similar on this last test; the Rodagon-D 2X (reversed) still will be in is designed working range, not like the other two lenses.

Rodagon D 75/4

f4           48 shots with 0.09mm steps  1/6

f5.6        30 shots with 0.15mm steps  0.3"

f8           25 shots with 0.20mm steps  0.6"

Rodagon D 75/4.5 reversed

f4.5        45 shots with 0.10mm steps 1/5

f5.6        30 shots with 0.15mm steps 0.3"

f8           25 shots with 0.20mm steps 0.6"

Olympus 80/4

f4           48 shots with 0.09mm steps 1/6

f5.6        30 shots with 0.15mm steps 0.3"

f8           25 shots with 0.20mm steps 0.6"­­­­

On this last crop series we can see similar results to those on the 2X test, maybe both the olympus and the Rodagon-D 1X got a little worst, starting to show some mild CAs. The Rodagon-D 2X probes to be very well balanced and in my opinion is best choice for high magnification shots. 

After reviewing test results we can see that when makers design a lens it is difficult to make it work well at different magnifications, they have to make choices. APS-C and 4/3 users may think the Rodagon-D 1X is best choice because of the superior resolving power in the center of the frame; however I do prefer the Rodagon-D 2X as it is a very well balanced  lens, for me this is an more important aspect than center resolution.

 What about the Olympus? Well; a very good quality lens, showing very good performance more similar to that of the Rodagon-D 1X. Its only con it that it is a rather difficult lens to adapt.

 On a OM bellows system  with this lens and the 38/2.8 you would have all you need from 0.5X to 6-7X. If your bellows system uses a different mount it can be a problem, it is quite difficult to find M42 or Nikon adapters.

You can always put together some pieces and make your own, problem being it also adds some extension; this can be a problem or not, depending on your needs.

OM to M42 DIY adapter

Nikola Rhame is well known for his beautiful studio stacks, showing always a perfect lighting technique. He has also conducted a few light experiments in his flickr, here we are going to show a couple of them:

Studio lighting comparison (flash vs. LED)

3000px version

Since I use two different lighting system for high magnification studio photography, was curious about the difference of the effects.
Well, I choose a tiny leaf miner jewel beetle from my collection and did two stacking sequence. One lit with a Speedlite 580EXII flash through a plactic diffuser around the subject, and another with 2 IKEA table LED lamps through the same diffuser. Find the picture of the setup below!

Shots were taken with a Mitutoyo BD Plan 10x microscope objective on a Apo-Gerogon 9/150 enlarger lens at 9,2x magnification. 105 exposures in each stacks. Shutter speed with flash: 1/100 sec. (live view mode), with LEDs: 1/3 sec. (live view, silent shooting mode).
I found no remarkable difference in the light effects. Perhaps when the flashlight is coming frontwise of the beetle looks more natural than the two separated light reflection. Another strange thing appears: the different color of the LED lamps. I have 4 Jansjö lamps and none of them has the same colors.
Then I looked at the stacks at the original resolution and surprised of the difference. I do not know why, the LED lit version has slightly finer and perhaps sharper details.

Crops from the original images:

Check out the comparison below side-by-side!

How the setup looked like:

Playing with the light

I am a big fan of diffusing the light when photographing insects. Most of the shiny subjects looks far better under drastically diffused flash or other lights. The tiny details of the surface pass off in spotted illumination, so I always prefer using white plastic or white office paper around the insects.

Now I wouldn't show example shots with absolutely pure lights, I hope each of you know the problem. As my favorite family of beetles are the jewel beetles, I have a lot of experiences in shooting them. In the nature they frequent sun-exposed places, like cut woods, flowers or dry trees. Pictures made under these conditions will be overcontrasted, too many black areas and shiny spots, loosing the nice sculpture details. You'd be better to photograph them in overcast or in early morning.
Excercise in the studio gives useful experiences which can be profitable in the field.
Jewel beetles (Buprestidae) are mostly colorful, metallic insects, they always look exciting if the light is well controlled. I obtained some routine with this small fellow a few days ago. It is a prepared leaf miner beetle -Trachys troglodytiformis choosen from my collection. Its length is 2,95 mm.
For the test stacks I used the JML 21/3.5 lens on a bellows set to 7x magnification. Two sequences were made, first with a whole paper cylinder, second with the same cylinder but with a hole on it, and a translucent paper fixed on the hole. Both stacks were combined in two stacking methods of Zerene: DMap and PMax, surprisingly the results are different in terms of lighting effect.
My edification is the excessive diffusing loses from the nature of the subject in some cases. Let's check the examples below!

Fully diffused stack, processed with DMap:

Fully diffused stack, processed with PMax:

Partially light-exposed stack, processed with DMap:

Partially light-exposed stack, processed with PMax:

And a synthetic crossed eye stereogram from the shiny stack:

2000px

These articles were originaly published by Nikola Rahmé on his flickr site, below you have the links to the original place

Studio lighting comparison (flash vs LED)

Playing with the light

 One of the first problems we have to face when completing a stack is finding out the number of shots needed. When in doubt many will possibly try to do it by eye,  which either will make them take more shots than necessary or fall short.

There are two formulas that will allow us to find out the depth of field (DOF)of every picture, once we know the depth of field ideally we will let shots overlap around a 20%.

The first of these formulas is known as Lefkowitz formula  2 * CoC * f *(( m + 1) /(m*m))

CoC refers to the circle of confusion; we will use approximate values of 0.030 for full frame cameras, a CoC 0,020 for cameras with APS-C sensors and a CoC of 0.15 for 4/3 cameras, these calculations are based on CoC = d/1500 where d is the diagonal of the sensor (43 mm in the case of full format sensors). The use of zeiss formula is also extended d/1730, with this formula the CoC for a full frame camera is 0.25

m refers to the magnification (0, 5 X 1 X etc.)

(f) refers to the aperture we work at (f2.8, f4, etc..)

Eg. for a full frame camera working at 0.5X and f4:  2*0.03*4*((0.5+1)/(0.5*0,5))= 0.06*4*6= 1.44mm

The is a nice DOF calculator based on this formula in Enrico Savazzi's website

Here a table showing the DOF for a full frame camera with a CoC of 0.030 at different magnifications;  I have rounded these values up to two decimals for convenience.

This would be the depth of field of each shot, we should overlap each shot around 20% so the stacking software can properly work and we can achieve maximum output quality.

Another formula used in microscopy, as can be seen on the nikon microscopy website is:

Where dtot is the total depth of field

l is thewavelength of the light source in micrometres , we use 550nm as it is the wavelentgh for which the human eye is optimized. We will use the same units that will be used for depth of field (micrometers), so the wavelength is 0.55 micrometers

n is the index of refraction of the medium, usually air (1); in microscopy is also frequent to use oil (1.515)

NA is the numerical aperture of the objective, marked in microscope objectives barrel

You can use this calculator to covert the f number to NA

M is the magnification we are working at

e is the smallest distance the sensor can resolve, normally here use the pixel size of your camera x 2, in the case of the 5d mkII 13 (6.4 x 2)

For example,   for a 4/0.10 microscope objective:

              0. 55 *1             1

         --------------- + -----------* 13 = 55 +(2.5*13) = 87,5 micrometers

             0.1 * 0.1       4 * 0.1

Compared to the previous results with the Lefkowitz formula for a  4 X at f4.8 the results are quite similar (0. 09 mm), although not the same.

The best way to find out what method works best for you is through experimentation, since each sensor behaves in a different manner; a method  that may work for me may not work for you.

Once we know the depth of field  we can determine the step size needed

For the previous example of a microscope 4/0.10 objective on a 5 d mkII  we would use  0,07 mm steps, which would make every shot overlap a 20% with the next. Now, we can either take pictures with steps of 0,07 mm until we have completed the stack or we can measure the DOF needed first (with an analog or digital micrometer, with this last one it is a very easy task). Once we know the DOF we just need to divide this by the size of each step. For example; lets say we want to photograph a subject whose depth is 2,15 mm with this 4/0.10 objective. We divide 2,15 by 0,07 mm which would give us 30.7; so we would take 31 pictures (to round up).

In addition to what we already said other factors may affect the depth of field; so again, experimentation is the only way we have to make sure what values work best for us.

There is an interesting thread in photomacrography.net that discusses this topic