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[Chicago Astronomer - Astro Joe]

Macro Imaging Using SLR Lenses

The bitter cold temps of Chicago Winters dictate that we keep busy indoors. Too cold for astronomy, (Used to stay out all night as a kid), but unless it's something rare, I'll wait until early spring to bare the brunt of biting winds and the cold kiss of telescope metal.

There are a host of accessories for the Canon Powershot S3 - got me a basketful already... I have my eye on the 3x teleconverters, but must heat the house instead, as they are quite expensive. They also have macro lenses available, but since I already possess zoom lenses from my Nikon 35mm film SLR, I thought I might experiment and see if they could be of any use.

Results were very good using lenses not meant for the S3 and the experimental images are as follows:

I used one of my old Chicago Police Lapel Pins from my glory days as an instructor... The pin has good detail and blue coloring to display any color changes and tilted it for shadow relief.

I used the following settings:

• Camera on manual
  
• ISO 400
  
• 1/40
  
• f-3.5
  
• Tungsten
  
• Vibrant
  
• Spot Metering
  
• 1600x1200
  
• 2 second timer
  

The following is the magnification sequence of the camera and with attached lenses.

Started out with the pin about 3 Ft away with wide aperture and no zoom...

Full Zoom (12x)

Full Digital Zoom (48x)

Macro Setting

Macro with full zoom

Super Macro Setting

Here I had the camera lens literally right on top of the pin - cutting out the illumination. I had to "sneak" some light in from under the lens to get this shot. Also...I needed to increase the ISO to 800 and slow down the shutter to 1/8

The following are with the Sigma Telephoto Lenses attached

80mm to 200mm Backward Lens

Zoomed to 200mm

Zoomed to 80mm

35mm to 70mm Backward Lens

70mm

35mm

Conclusion:

I attached the Sigma lenses "backwards", connected to the S3 lens adapter. For this experiment, I used simple clear postage tape.

Normally the higher the mm, the more magnification one gets, but backwards, it's just the opposite inversely. The smaller zoom (35/70mm) provided more magnification than the heftier 80/200mm zoom lens.

I used the tripod to garner rough focus distance and then using the camera's focus control. Finally right before the shot, I used the lenses focusing ring to squeeze the last bit of focus sharpness. I also kept the f-stops on the lenses wide open for this test, but closing them down provided good depth of field control...better than the cameras electronic f-stop setting.

I am quite satisfied on the performance of the "backward" lenses and just now need to create an adapter to attach them to the S3 for intricate and facinating macro world imaging. It was well worth the time this afternoon to increase the capability of the S3.

I wonder if i can adapt this technique to the telescope? When it gets warmer I'll conduct some more experiments.

[Erik]

You'd probably get the best ratio of magnification to dof by using a wide prime lens rather than a zoom, sharper too.

[Chicago Astronomer - Astro Joe]

Erik,

Well, I used what I had, the two zoom lenses. And it was an experiment of already owned lenses and they do work as something they were not meant for.

I'm satisfied on the performance and zero cost.

Thank for the input...