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Old May 30, 2006, 6:07 PM   #1
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How does one calculate it or is there a database somewehre for them? thanks
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Old May 31, 2006, 4:23 AM   #2
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The Nikon DSLRs have a sensor ratio of 3:2 printing at multiples of these numbers will give you a full frame print 6x4 9x6 12x8 are all 3:2 reproduction ratio.

If you print a 7x5 or 10x8 you will need to crop to fill the page.

Most compacts have a 4:3 ratio which doesn't fit the common paper sizes very well they will print full frame at 4x3 8x6 12x9.



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Old May 31, 2006, 8:26 AM   #3
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thanks, but i meant reproduction ratios of lenses, like the micros can all focus to 1:1.
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Old May 31, 2006, 2:43 PM   #4
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That makes it a little clearer but I don't understand the question. The reproduction ratio is normally given by the manufacturer in the lens specs.

With a Nikon DSLR you have a smaller sensor than with 35mm film so you get a 1.5x crop factor but a 1:1 lens is still 1:1 it's just that the area it covers is smaller.

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Old May 31, 2006, 9:14 PM   #5
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Unless you're shooting macro, I don't know that this info is truly necessary. I can't think of a time outside of macro shots where I've ever needed or even cared about reproduction ratio. Why do you feel this is important to know??
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Old Jun 9, 2006, 1:45 PM   #6
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I would imagine that to achieve a reproduction ratio of 1:1 with a 105mm macro lens on a digital SLR with a 1.5X conversion over 35mm equivalent would require taking the picture from 157.5mm away from the subject: 105mmX1.5 =157.5mm effective focal length. 157.5mm focal length/ 157.5 shooting distance = 1:1 reproduction ratio... Anyone care to comment on my reasoning?
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Old Jun 9, 2006, 2:10 PM   #7
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Effective focal length ie: the crop factor is virtual.

A 100mm lens is still physically a 100mm lens and acts like it.
Not sure what the focusing distance has to do with the macro capablity.
Ie: the Sigma 180mm macro lens has a minimum focusing distance of 46cm/18.1in (460mm) and that is where it achives 1:1. It does not matter what camera format/sensor size it is mounted on.

Similarely the Sigma 105mm macro close focus is at 31.3cm/12.3 in (313mm).

The Sigma 180mm macro close focus is at 46cm/460mm
The Tamron 180mm macro close focus is at 47cm/470mm
The Canon 180mm macro close focus is at 48cm/480mm
Three macro lenses with the same focal length, three different minimum focus distances.
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Old Jun 9, 2006, 2:19 PM   #8
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Actually, he's got a point.

If you use a Macro lens on a DSLR that's designed to provide 1:1 Macro on a 35mm camera, you're effectively getting more than 1:1 Macro, since 1:1 is typically regarded as being able to fill the frame with a subject the size of the film or sensor used, and focus distance won't change with a smaller sensor.

His logic for focal length/focus distance appears to be wrong though.

The Nikkor 105mm f/2.8D AF Micro Lens has a closest focus distance of 1 foot:

http://www.nikonusa.com/template.php...productNr=1988

That works out to approximately 305mm.

It's a 1:1 Macro Lens.

It's designed to work with a 35mm camera, too.

Focus Distance won't change with sensor size.

However, your subject would fill more of the frame using a Nikon DSLR (since you'll have a narrower angle of view with a sensor smaller than 35mm film).

So, in reality, it's better than 1:1 Macro when used on Nikon DSLR.

In order to get back to 1:1 (fill the frame with a subject the size of the film or sensor), you'd need to shoot from approximatley 50% further away. That puts you at around 457mm from your subject.

Let's take another 105mm lens.

The Sigma 105mm f/2.8 EX DG Macro Lens has a closest focus distance of 12.3 inches or 313mm.

http://www.sigmaphoto.com/lenses/len...mp;navigator=5

It's a 1:1 Macro Lens

It's designed to work with a 35mm camera, too.

Focus Distance won't change with sensor size.

So, in reality, it's better than 1:1 Macro when used on a Nikon DSLR.

In order to get back to 1:1 (fill the frame with a subject the size of the film or sensor), you'd need to shoot from approximatley 50% further away. That puts you at around 470mm from the subject.

There are likely some minor differences between them that account for the focus distance changes (for example, slightly different angle of view, or rounding used for declared focus distance, or one lens may be slightly better or worse compared to another for true 1:1 macro subject size).

I'm sure there are some optics experts around that know the formulas for this kind of thing. I just do it the easy way (check the focus distances in the specs, since they should be 1:1 at the minimum focus distance). ;-)


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Old Jun 9, 2006, 2:45 PM   #9
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:-)I think I have a problem with your logic.

1:1 means it is life sized, it does not mean it fills the frame.
A shot of a 1mm frog eye will take up 1mm on a 35mm sensor.
I do not think this changes with the smaller aps-c sensor, the 1mm frog eye still should record as 1mm, you just get less of the surounding frog recorded on the smaller sensor.

Of course I may be wrong :? I don't do much macro work.
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Old Jun 9, 2006, 2:58 PM   #10
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Ifa subjectfills the frame, then it's the same size as the film or sensor. ;-)

For a definition:

http://en.wikipedia.org/wiki/Macro_photography

Edit/Added:

I hate to send people elsewhere. But, Vincent touches on sensors smaller than 35mm film here:

http://www.dpreview.com/learn/?/Glos...l/Macro_01.htm

Maybe my thinking is flawed. :-)

But, from my point of view, a 1:1 Macro Lens designed for 35mm models would be a 1.5:1 Macro Lens when used on a Nikon DSLR.

Or, an exotic lens like the Minolta 3x-1x f/1.7-2.8 AF Macro would become a 4.5x - 1.5x lens on a KM DSLR model (capable of 4.5:1 Macro).

The definition will probably "evolve" over time, given the number of different sensor sizes we have anymore, since there is a gray area in there with the focal length multipliers for equivalent angle of view (is the subject really larger than lifesize with a smaller sensor or not, and is lifesize how big it is on the sensor, or after enlargement to a standard viewing or print size).

I think it needs to evolve so that the definition is transferrable to a standard print or viewing size for macro magnification purposes, since you can have more or less apparent magnification for a given focal length lens with a difference in film or sensor size.


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