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1:1 versus 1:2 macro (or is it 2:1)
I know very little about macro lesnes for SLRs..

I have noticed some are designated at 1:1 and others at 1:2. What does that actually mean. It seems to me that with a fixed focal length macro, that the size of the image will vary depending on how close you get?.

Let's say you are photographing an ANT, that is about 1/2" long... How would that be different in appearance in the viewfinder of a 1:1 versus 1:2 lens?.

Thanks..

Peter F...

Comments (10)

1:1 means the lens has the ability to focus on a subject to get a same sized image on your sensor as is the subject. 1:2 means the 1 inch ant can only be up to a 1/2 inch image on your sensor. Two things control this: How close a lens can be to and focus on any subject, and to what extent the lens is magnifying the subject. Thats the short answer. For myself, the attainment and control of DOF (depth of field/focus) is the big issue in all of macro work...Good Luck..

Comment #1

Thanks, I get the idea. But it still seems to be a difficult concept since different cameras have different sized sensors and more/less pixels. For example, half the size on a 12 pixel image can be cropped to equal the full size on a 6 pixel picture... I would think but maybe it is more complicated than that..

Anyway, since much of this stuff comes from the old days of 35mm, I can see how it would be an easier concept "back then" as 35mm was the only film used in 35mm cameras. Today we have dSLRs with 4/3 format, APS format and FF format. Yikes...

Comment #2

Cropping it isn't going to give you 1:1 magnification. You'll have a larger copy of a 1:2 magnification, that's all. Nor does the sensor size matter for magnification. It's not a 35mm concept... it's 1:1 magnification..

And true macro is defined as 1:1. Lens manufacturers are now using the term macro more broadly with 1:2 etc just to promote a close focusing ability. Kind of like compacts advertising as 10x zoom...

Comment #3

The 1:1 is simply a ratio. So are the 1:2 and 2:1 numbers. The size of the recording medium has nothing to do with it..

If the subject is life size on the sensor, it is a 1:1 shot. If it is twice life size, it is a 2:1 shot..

As has been stated, the term has been adulterated in common use. 1:2 is not macro. Macro starts at 1:1 and goes up..

Crime Scene PhotographyA small gallery of personal work: http://picasaweb.google.com/PID885..

Comment #4

Caoedhen wrote:.

The 1:1 is simply a ratio. So are the 1:2 and 2:1 numbers. The sizeof the recording medium has nothing to do with it..

Image_Size:Object_Size is the format; it is "magnification".

While what you say about it simply being a ratio is true, I think in quantitative photographic optics it usually refers to the maximum image size one can get on the sensor. In this sense it refers to a 100% crop..

It makes a difference because certain photographic optics relationships are non-linear functions of magnification. Depth of Field in particular behaves differently with magnification, m, when m is much less than 1 than when it is greater than 1..

(Depth_of_field/Width_of_field)= (2cf/sensor_width)(1+1/m).

Where c is "circle of confusion" and f is f-stop; Depth_ and Width_of Field are real distances in object space.

It is also helpful to just think of the ratio as how much of the object fills the un-cropped frame;.

1:1 the object's image fills the frame1:2 the object's image half fills the frame..

Comment #5

Dave Martin wrote:.

It is also helpful to just think of the ratio as how much of theobject fills the un-cropped frame;.

1:1 the object's image fills the frame1:2 the object's image half fills the frame.

It does not have to fill the frame to be 1:1. If you are photographing something physically smaller than your sensor size then it will not fill the frame but can still be of 1:1 magnification...

Comment #6

Just to answer the question in your subject line - it's 1:2..

There is an easy way to remember - 1:2 looks very much like 1/2, and sure enough it means half size...

Comment #7

PeterNMIF wrote:.

Thanks, I get the idea. But it still seems to be a difficult conceptsince different cameras have different sized sensors and more/lesspixels. For example, half the size on a 12 pixel image can becropped to equal the full size on a 6 pixel picture... I would thinkbut maybe it is more complicated than that..

You are right that sensor size is as important as mag ratio!.

[However, to crop the area of a 12MP image to equal twice magnification you would have to crop to a 3MP zone... 1/2 the height AND 1/2 the width, remember... leaving only 1/4 of the area you started with.  ].

Leaving that aside.....

What matters in macro shooting is how SMALL of a thing will fill the sensor size (whatever that is) and whether the lens will actually focus CLOSE enough to do the task..

So, if a subject is 1.5 inches across, say.....

(hmmm... these ants are getting seriously large!).

...... it will fill the FF35mm camera frame when shot Same Size as in life.. what we call 1:1 magnification. This is because a 35mm film frame happens to be just 1.5 inches (36mm) from one end to the other..

However, when that same one-and-half-inch ant is fitted into a 2/3 sensor....

(8.8mm x 6.6mm, as in the Konica Minolta A2/A200 of a coupla years back).

... it can be made to fill the frame in exactly the SAME way, same composition/framing etc. but it will do it at only 1/4 of life size.... or a ratio 1:4..

The magnification ratio is "different" because the size of the frame is different! In framing terms the shot however is the same in each case... but with much additional Depth of Field in the smaller-sensored camera..

Now, if the ant were only 8.8 mm long (more like the size I'm used to!) then it will FILL FRAME at 1:1 on the A2.....

..... but require an even higher mag ratio to do so on APS [3:1]...... or FF cameras [4:1].

Q: Does this mean that a common 1:1 ratio is somehow *more magnification* on a smaller frame like APS, than it is on a full frame sensor?.

A: Well... the complete answer to this is both "Yes" and "No"..

YES .... It is larger because it is cropped to show less of the subject area, and, when the print is made to 10x8" and viewed in the normal way, magnification of that lesser area will be greater..

In a nutshell.... What you see will be less, but it will be seen in more detail.  .

NO .... It is NOT any larger in *image on the sensor* terms. 1:1 is one to one, no matter how much area is involved in the sensor you are using. However, framing will be different (see above)...and since nobody ever VIEWS images at the titchy little sensor sizes we now most often use....

... it really is high time we stopped using magnifications ALONE as indicating anything useful..

What we really need to know when shooting macros is what WIDTH of subject field will FILL the image field... which depends on two factors....

1) Subject's image-size ratio as it falls on the sensor (magnification ratio)2) Absolute linear size of the sensor itself.Regards,Baz..

Comment #8

When a lens says it is a 1:1 macro lens it means that it'll project an image on the image plane that's the same size as the object in the object plane..

Image_size:Object_size; a ratio of actual sizes..

It makes no reference to how you magnify or demagnify the image thereafter..

Say I take a lens and make a 1:4 image with it; ie. the image is 1/4 life size. Now I enlarge that image 20 times; the image is now 5 times life sized..

Be that as it may, the original image cast by the lens is still 1:4, ie. the image cast by the lens was 1/4 life size...

Comment #9

Dave Martin wrote:.

When a lens says it is a 1:1 macro lens it means that it'll projectan image on the image plane that's the same size as the object in theobject plane..

Image_size:Object_size; a ratio of actual sizes..

It makes no reference to how you magnify or demagnify the imagethereafter..

Say I take a lens and make a 1:4 image with it; ie. the image is 1/4life size. Now I enlarge that image 20 times; the image is now 5times life sized..

Be that as it may, the original image cast by the lens is still 1:4,ie. the image cast by the lens was 1/4 life size..

That reads more clearly to me and I whole heartedly agree..

If a lens is capable of 1:1 then it doesn't matter what the sensor size is. The image projected to the sensor plane will be of 1:1 magnification when shot as such. Whether the appropriate sensor size is there to capture the image is not an issue of the lens being 1:1 capable..

And so yes, on a smaller sensor that could result in a cropping of the intended subject image but if you attempt to recompose then you are no longer shooting macro as defined as 1:1..

That is undoubtedly one of the banes of using EF lenses on APS-H and APS-C bodies. That and using what are normally wide angles...

Comment #10

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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