Kiron 28-70mm f3.5-4.5 Macro For Reverse Zoom Macro (Images)

Harold Gough · Post by **Harold Gough** » Wed Oct 17, 2012 10:41 am

So far, I have tested this lens only on 110mm extension at f11 and at focal length 70mm. This extension in prior checks gave a field of view 3mm wide at 28mm and 10mm wide at 70mm focal lengths.

This shows some images from the sesssion:

http://www.photomacrography.net/forum/v ... 993#116993

Here are some of Areneus spiders at the same magnification. As using flash on the hotshoe prevents use of the VF-2 high resolution viewfinder, I was left using the rather poor rear live view screen. Thus focusing was very much hit and miss.

Images uncropped.

Harold

Harold Gough · Post by **Harold Gough** » Wed Oct 17, 2012 11:07 am

Here is another image from the same session. this time, the stigmae and pollen of a Hollyhock.

Uncropped.

Clearly, this is one for stacking.

Harold

Harold Gough · Post by **Harold Gough** » Wed Oct 17, 2012 11:35 am

Here is the finer Clematis featured here:

http://www.photomacrography.net/forum/v ... 599#114599

Slightly cropped.

Harold

Harold Gough · Post by **Harold Gough** » Wed Oct 17, 2012 11:42 pm

The working distances under this configuration are 45mm at 28mm and 65mm at 70mm.

Harold

Harold Gough · Post by **Harold Gough** » Thu Oct 18, 2012 1:17 am

This was shot with the same setup as yesterday (zoom at 70mm), except:

1) The flash was fitted with a dedicated diffuser.

2) The flash was mounted on a tripod clamp ring (designed for clamping lenses to tripods) so that its front was about level with the lens mount (nearest subject) and angled downwards at 45 degrees or thereabouts.

3) A hotshoe extension lead with an OM TTL cord connected to the back of a T20 hotshoe, attached, in turn, to the tripod thread of a tripod-mount flash hotshoe accessory.

4) The proximity allowed the ISO to be dropped to 200 from the 800 used up to this point.

5) The rather wobbley grip and unreliable aim of the gun on the camera hotshoe, and its metering ability, were thus regularised.

FOV 10mm wide. Hand-held, manual flash 1/160 sec.

As I hadn't got the subject quite in the same plain as the sensor, I have cropped off the top of the image:

A reshoot (below) shows the aperture to have been f8, not f11 as I believed.

Harold

Harold Gough · Post by **Harold Gough** » Thu Oct 18, 2012 1:48 am

With all the images from this lens posted so far, I have had to struggle to frame them. let alone focus, due to gusty winds. A slight pause in the wind permitted further shots, at f11 but ISO 400.

Uncropped:

Although the plane of focus is still what I would hope for, it is better. There is a lot of fine detail captured.

Harold

Harold Gough · Post by **Harold Gough** » Thu Oct 18, 2012 2:31 am

I didn't get an acceptable result yesterday for these stamens of a Japanese Anemone perennial.

FOV 10mm wide, uncropped. Diffused flash ISO 400, hand-held, FL 70mm.

Harold

Harold Gough · Post by **Harold Gough** » Thu Oct 18, 2012 4:42 am

I have taken further shots of the stamens. This time I have zoomed the lens out to 28mm, giving a FOV 3mm wide. I retained the f11 and increased ISO to 800.

Partly because of the inherent difficulty of hand-held photography at this magnification and partly because of windy conditions, I detached the flower and placed it on a conservatory bench. Thus I had considerable, steadying support for camera and subject and no wind to contend with.

These are uncropped:

It is my conclusion that working with this 3mm FOV is impractical for most field use and it would be better to work with a shorter extension, and lower ISO, except inexceptional circumstances.

Harold

Harold Gough · Post by **Harold Gough** » Fri Oct 19, 2012 1:15 am

Update and correction:

There are two red lines on the aperture ring and I believe that the f11 was, in fact half a stop larger. This post uses f11.

The diffuser for the T32 flash is like a rectangular box, the open end sliding onto the front glass of the flash. Made of white plastic, it protrudes forward some 25 mm/1". This means that light emerges from not oly the front panel but all four side ones. Wonderful for studio work but a waste of light for macro.

So I wrapped some cooking foil around it, as a kind of snoot, extending forward by about 10mm beyond the front of the diffuser to further direct the light. This was such a saving of light that, with the previous flash setting, even at ISO 100, I was getting overexposure. So I set the gun to manual, half power (GN16). This gave spot-on exposure.

Here is a shot (FL 70mm, FOV 10mm wide) of a fruit of this plant:

http://www.rhs.org.uk/Gardens/Wisley/Ab ... -Profusion

Here is the image straight from the camera, only its size modified for posting:

So, not more ISO 400 or 800 and no concerns about what was being metered. This is what I used for film before TTL flash and it was with twin flash, shortly to be introduced into this project.

Harold[url]

Harold Gough · Post by **Harold Gough** » Sat Oct 20, 2012 8:41 am

Today I added a second, smaller flash gun via a second lens tripod clamp. This was a T20, connected to the other flash and the camera via an OM 3-way TTL connecter and cord. The diffuser was four layers or white packing materia, which feels like tough rubber foam.

Both flash guns were on manual, the T32 on half power.

An initial test showed that the combined light intensity from this flash setup was correct for f11 at ISO 100 but it was found that correct exposure was given by f16. Most (possibly all) shots were at f16.

Japanese Anemone stamens, as shot previously at f11:

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Further shots of flies are posted here:

http://www.photomacrography.net/forum/v ... 104#117104

Harold

Harold Gough · Post by **Harold Gough** » Sun Oct 21, 2012 3:57 am

Here is a springtail Tomocerus sp at f16, FOV 10mm wide. I didn't quite get the dorsal surface sharp but this shows the potential. This has been heavily processed so the image quality is not the main interest this time. Those dark, plate-like structures are striated scales.

It is unusual to find one posing like this and remaining still for several shots. Maybe it will return to the same place.

Harold

Harold Gough · Post by **Harold Gough** » Fri Oct 26, 2012 6:16 am

Things are getting better:

http://www.photomacrography.net/forum/v ... 476#117476

Tomocerus ones to follow.

Harold

Harold Gough · Post by **Harold Gough** » Fri Oct 26, 2012 7:54 am

Here are some better Tomocerus ones, probably a different species:

http://www.photomacrography.net/forum/v ... 480#117480

Harold

Harold Gough · Post by **Harold Gough** » Sun Oct 28, 2012 3:51 am

I recently came across an f4, constant aperture, oversion of this lens. I considered it briefly and then checked hiow my 3.5-4.5 performed on this setup.

Within the limits of the camera's display, the brightness at 28mm is 50% greater than at 70mm, both at closest focusing. Thus the image is brighter at the higher magnifcation, where it is more critical for focusing and where a smaller aperture may be needed for DOF.

Harold

Harold Gough · Post by **Harold Gough** » Sun Oct 28, 2012 8:36 am

Harold Gough wrote:I recently came across an f4, constant aperture, oversion of this lens. I considered it briefly and then checked hiow my 3.5-4.5 performed on this setup.

Within the limits of the camera's display, the brightness at 28mm is 50% greater than at 70mm, both at closest focusing. Thus the image is brighter at the higher magnifcation, where it is more critical for focusing and where a smaller aperture may be needed for DOF.

This has been found to be the case:

http://www.photomacrography.net/forum/v ... 588#117588

Harold