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04-05-2009, 08:03 PM   #1
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whats the difference? 1:1 vs. 1:2 macro

I just purchased a macro lense FA 100mm f3.5. I know 1:2 is inferior, but is there a big difference regarding with the image quality? Any suggestions too on how to improve the image quality. thanks.

04-05-2009, 08:13 PM   #2
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QuoteOriginally posted by metungnasi Quote
I just purchased a macro lense FA 100mm f3.5. I know 1:2 is inferior, but is there a big difference regarding with the image quality? Any suggestions too on how to improve the image quality. thanks.
1:2 isn't inferior. It has to do with magnification or how close you can get to the subject.

Larry
04-05-2009, 08:18 PM   #3
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A true "macro" lens usually has the ability to get down to 1:1 (the Bokina needs an adapter to do this).
Some companies that make regular lenses claim Macro capability for anything less than 1:4 IIRC but they can only go down to 1:2 at most...
04-05-2009, 08:41 PM   #4
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QuoteOriginally posted by larryinlc Quote
1:2 isn't inferior. It has to do with magnification or how close you can get to the subject.

Larry
Specifically, the image size for a 1:1 lens is twice the image size for a 1:2 lens.

Further, 1:1 image is formed when the lens is 2 focal lengths from the subject while a 1:2 image is formed when the lens is 3 focal lengths from the subject.

Iowa Dave

04-05-2009, 10:08 PM   #5
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Like the other posts say, the difference is in magnification. A macro lens that can do 1:1 magnification means your image can be the same size as the camera's sensor, 24mm wide. With your lens, a 24mm-wide subject can only be magnified to fill half the frame. With larger subjects or greater distances, that limitation doesn't matter. The ratio will only affect IQ if you try to crop and magnify your image in processing to get to 1:1.

As for increasing IQ with your lens, you want to use an aperture that gives you enough depth of field to cover the subject. Up close, that might be a pretty small aperture, like f16 or f22. Your shutter speed might end up pretty low at those apertures, so you may need to raise ISO. Try to limit camera movements as much as possible, with bracing, a tripod, macro rails, etc. A flash is useful if you have one and can get it aimed at the subject. Sometimes switching to manual focus helps.
04-05-2009, 10:31 PM   #6
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The 100/3.5 can provide very good macro results with proper technique:

-- Focus manually for magnification greater than 1:4 or so.
-- Stop down. Until it hurts. AV mode f/11-f/16 is a good place to start.
-- Do one of the following:
(1) Use a tripod if your subject isn't moving or swaying in the wind
(2) Increase the ISO until you get a shutter speed fast enough to hand-hold (ISO 800, 1/50s-1/100s)
(3) Use the built-in flash and ISO 100. The flash eliminates camera shake problems but it can give your subject a "floating in space" look. I've found with this lens (actually, the Phoenix/Cosina equivalent) I need to set +2EV exposure compensation when the barrel is fully extended.


You can use 50mm of extension tubes to get to 1:1 magnification but it's much more convenient to use a high-quality close-up lens instead. Promaster sells a close-up lens for exactly this purpose.

Link to the matched close focus adapter that came with the phoenix, cosina, and vivitar versions

Last edited by troyz; 04-06-2009 at 07:13 PM.
04-06-2009, 04:42 AM   #7
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QuoteOriginally posted by newarts Quote
Specifically, the image size for a 1:1 lens is twice the image size for a 1:2 lens.

Further, 1:1 image is formed when the lens is 2 focal lengths from the subject while a 1:2 image is formed when the lens is 3 focal lengths from the subject.

Iowa Dave
This is interesting. But I must be understanding this wrong.

Let's take the sigma 105.2.8 which has a focal length of 105mm, closest focus distance of ~310mm, and is 1:1 macro.

Are you saying a 105mm lens has to be 210mm from the subject to achieve 1:1, then the specs. above cannot be right.

Also, when you say the lens has to be 2 focal lengths away, is it the front element of the lens or the camera sensor ?

Can you please elaborate, or post a link where they talk about this.

Thanks.
04-06-2009, 05:08 AM   #8
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Thanks a lot for all your post. Im a beginner with SLR cameras. All the advices are really much appreciated.

04-06-2009, 06:00 AM   #9
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The relationship between distances, focal length and magnification m is:

Sensor_subject_distance = focal_length(1+m)(1+m)/m

Lens_subject_distance = focal_length(1+1/m)

The first relationship holds for all lenses, while the second one is more difficult to apply because it is hard to know the exact location of the optical center of a complex lens (eg. it moves with internal focus lenses).

The number written on the side of the lens (like ,43m) is the minimum sensor_subject distance.

Iowa Dave

PS these are easy to derive from the thin lens equation and the definition of magnification:

1/Focal_length = 1/Sensor_lens_distance + 1/Lens_Subject_distance

m = Sensor_lens_distance/Lens_subject_distance = Image_size/Subject_size

Last edited by newarts; 04-06-2009 at 09:32 AM.
04-06-2009, 06:00 AM   #10
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QuoteOriginally posted by pcarfan Quote
This is interesting. But I must be understanding this wrong.

Let's take the sigma 105.2.8 which has a focal length of 105mm, closest focus distance of ~310mm, and is 1:1 macro.

Are you saying a 105mm lens has to be 210mm from the subject to achieve 1:1, then the specs. above cannot be right.

Also, when you say the lens has to be 2 focal lengths away, is it the front element of the lens or the camera sensor ?

Can you please elaborate, or post a link where they talk about this.

Thanks.
you need to check whether the closew focus distance is based on distance from front of lens, or camera.

1:1 is achieved when the subject is 2x the focal length from the front of the lens.
04-06-2009, 09:26 AM   #11
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If I use a 1:1 macro lens on an APS camera, does that mean that it is really a 0.75:1?
04-06-2009, 09:31 AM   #12
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QuoteOriginally posted by Lazaruscomeout Quote
If I use a 1:1 macro lens on an APS camera, does that mean that it is really a 0.75:1?
No.

1:1 is the ratio of subject size to image size. the crop factor of the sensor is independant
04-06-2009, 09:46 AM   #13
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Here's a real world example...

Take an ordinary US first class postage stamp. The dimensions of the printed area on one I have in front of me are 23x18mm (very close to the dimensions of the APS-C sensor in the current Pentax DSLRs 23.5x15.7mm).

If you make a photograph with a 1:1 macro lens at its minimum focus distance the printed area of postage stamp will "perfectly" fill the entire area framed by your photo.

If you make a photograph with a 1:2 macro lens at its minimum focus distance the printed area of postage stamp will "perfectly" fill 50% of the area framed by your photo.
04-06-2009, 10:24 AM   #14
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Try to find the matched close focus adapter that came with the phoenix, cosina, and vivitar versions. You will get 1:1 with very little degradation in quality.
04-06-2009, 03:17 PM   #15
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QuoteOriginally posted by Lowell Goudge Quote
No.

1:1 is the ratio of subject size to image size. the crop factor of the sensor is independant
Of course, that makes sense. Although, it has a similar effect in that I can fill my APS sensor with a smaller subject than I could with the same lens on a full frame.
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