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[OM] Re: Mini Macro questions

Subject: [OM] Re: Mini Macro questions
From: "Scott Peden" <scotpeden@xxxxxxxxxx>
Date: Sat, 10 Mar 2007 08:36:16 -0800
        I understood most of that, I'll have to do more digesting on the
first part and ask a couple more questions when I get home. 

        I've got to get some better shots of some new tiny deciduous ferns I
found in the park, and seeds on some weeds to prove to a non botanically
inclined scientist that I know what I'm talking about botanically.

        Oh who cares, I get to go mess around in the Park with my
camera......

Scott


-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On Behalf
Of Moose
Sent: Saturday, March 10, 2007 4:32 AM
To: olympus@xxxxxxxxxx
Subject: [OM] Re: Mini Macro questions

Scott Peden wrote:
> The EX 25, is a 25 mm tube that allows the e-series lens?s to still
> communicate. Yes?
>
> It gives a 2:1 image,,, does that mean 2X life size or ½ life size?
>   
You are slipping into tricky territory here, not the reality, but the 
terminology.

Reproduction ratio numbers actually refer to the linear measurement 
relationship between subject and its image on the film/sensor.

If you use a 50 mm lens 100 mm from the sensor, the subject will be in 
focus 200 mm from the sensor and the physical dimensions of the image 
will be the same as the subject. This is a 1:1 repro ratio, and is not 
dependent on the size of the film/sensor. If the image on the film 
sensor is 1/2 the subject size, 1:2 twice the subject size, 2:1

However, if you take a pic of an object 1/4" across, it will take up a 
much smaller part of a 35 mm frame than of a 4/3 sensor. So if you 
enlarge both images to the same height, the object will appear about 
twice as large on the print from the 4/3 image as on the one form the 35 
mm film/sensor.

That means that a subject 3/4 inch tall may be photographed with the 35 
mm frame, but will not fit on the 4/3 sensor. It also means that the 4/3 
image will have been enlarged twice as much, so any flaws like grain or 
noise will be equally enlarged. it's all trade-offs, with no free lunch.

That's what Oly means when they in the EX-25 instructions:

"When the EX-25 is used in combination with the ED50mm f 2.0 MACRO lens,
pictures can be taken at close to 1:1 magnification (0.98 X) (equivalent 
to 2:1
magnification with a 35 mm film camera)."
> The 65-116 auto telescoping tube.
>
> Does that mean it gets even closer or more times life size than the EX 25?
>   
Yes, the longer the extension, the greater the theoretical possible 
magnification. The Auto tube is,as its name indicates, a variable 
extension tube with a range of 65-116 mm. It's not all that useful with 
a 50 mm lens unless you have an OM mount reversing ring. It's really 
designed for the true macro lenses shown in the "Bellows" column here 
<cid:part1.02020106.06030001@gmail.com>.

Although more awkward in the field, the bellows is much more flexible, 
with an extension range of 36-198 with normal lens mount and 56-218 mm 
with a reversed lens. I also will mount reversed lenses with 49 mm 
filter threads, like many Zuikos without any adapter.
> This is of course a manual lens, verses the EC 25 being an auto on a
> E-Series, correct?
>   
Correct on an E series with a non-reversed ZD lens. Both Auto Tube and 
Auto Bellows, as their names say, support auto aperture with OM lenses 
on OM bodies. With reversed lenses, nothing is auto.

Moose

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