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05-09-2008, 07:34 AM   #1
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Defining true 1:1 macro

I'm going to make some statements that I believe to be true so that anyone can correct me.

True 1:1 macro means that an object is reproduced life size on the sensor. So if you take a photo of a millimeter ruler with zero on the left and 24 on the right, that's a true 1:1 macro (because our sensors are 16x24mm). The same photo with 48 on the right would be a 1:2 macro, and so on.

The same photo with 36 on the right would be a 1:1.5 macro, even though it would be a 1:1 on a 35mm or FF camera.

Last thing, a 1:1 macro lens on a 35mm also functions as a 1:1 macro lens on a dSLR.

So, is all that correct?


Last edited by joefru; 05-09-2008 at 11:41 AM. Reason: Clarification
05-09-2008, 08:26 AM   #2
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you have got it. just so every one remembers the 0-36 mm on a film camera would be with the same lens, and subject distance as the 0-24mm on a dslr.
05-09-2008, 09:45 AM   #3
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QuoteOriginally posted by joefru Quote
I'm going to make some statements that I believe to be true so that anyone can correct me.
All correct! :-)

Or, here is how I remember it: 1:1 macro will precisely frame 24x36mm subject at the closest distance on film (or 16x24mm on APS-C, or 4.5x6cm medium format, etc...). Obviously, film/sensor size does not change magnification ratio. That is, 1:1 stays 1:1 no matter what captures projected image.
05-09-2008, 12:01 PM   #4
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I just did a quick and dirty test with a ruler and my Tam 90mm just to see it myself as I'd never put the math to work before. When I focus down to 1:1 with this lens and my K10D I'm getting only 22mm visible in the viewfinder. Is this due to some cropping going on with the viewfinder itself?
I was doing this test handheld so didn't bother with taking the shot as there's no way I could have kept it in any proximity of in focus. LOL

05-09-2008, 12:18 PM   #5
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QuoteOriginally posted by Venturi Quote
I just did a quick and dirty test with a ruler and my Tam 90mm just to see it myself as I'd never put the math to work before. When I focus down to 1:1 with this lens and my K10D I'm getting only 22mm visible in the viewfinder. Is this due to some cropping going on with the viewfinder itself?
I was doing this test handheld so didn't bother with taking the shot as there's no way I could have kept it in any proximity of in focus. LOL
If memory serves, is because you only get 95% viewing area through the viewfinder, If it was 100% then it would be 24mm. I know this is 10% rather than 5% but we are talking MM and it might be slightly more than 22mm you can see
05-09-2008, 12:19 PM   #6
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QuoteOriginally posted by Venturi Quote
When I focus down to 1:1 with this lens and my K10D I'm getting only 22mm visible in the viewfinder. Is this due to some cropping going on with the viewfinder itself?
Yes. The K10D's viewfinder gives "only" 95% coverage, so the actual picture is a bit wider & higher than what you see.
05-09-2008, 12:20 PM   #7
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Just a guess but I think the viewfinder is 95% on the K10D. If I'm not mistaken that means that you miss 5% of the image so maybe 22mm might be just about right.
Guess I responded before seeing if any else did. And I was right!! :gives self pat on back:

NaCl(guessing here, but it seems right to me)H2O

Last edited by NaClH2O; 05-09-2008 at 12:22 PM. Reason: added "guess I...."
05-09-2008, 01:09 PM   #8
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Thanks. I had seen the 95% figure tossed around but wasn't quite sure of the context. Now it makes sense. And yeah, 22.8mm would be a true 95% so given my own wobble while holding the camera that's right in line.

05-11-2008, 10:45 AM   #9
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APS-C = bigger magnification?

QuoteOriginally posted by Lowell Goudge Quote
you have got it. just so every one remembers the 0-36 mm on a film camera would be with the same lens, and subject distance as the 0-24mm on a dslr.
If that's all true (and I'm not arguing it isn't) it means that if you take the same lens (say Tammy 90), put in on K10D take 1:1 shot of the ruler, then put it on FF camera take the same scene 1:1, do no PPing, and take the pics to be developed straight out of camera, on normal 4x5 print the subject from APS-C sensor would appear bigger right?

Because from APS-C you only have 24mm to fill the 5" of the print while from FF you have 36mm to fill the same 5".
Is this assumption correct?
05-11-2008, 11:10 AM   #10
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QuoteOriginally posted by axl Quote
If that's all true (and I'm not arguing it isn't) it means that if you take the same lens (say Tammy 90), put in on K10D take 1:1 shot of the ruler, then put it on FF camera take the same scene 1:1, do no PPing, and take the pics to be developed straight out of camera, on normal 4x5 print the subject from APS-C sensor would appear bigger right?

Because from APS-C you only have 24mm to fill the 5" of the print while from FF you have 36mm to fill the same 5".
Is this assumption correct?
Correct. That's because the APS-C sized picture is being enlarged 1.5 times more (linear) than the FF picture in the print process.
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