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11-03-2009, 04:46 PM   #1
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Macro question

Not sure if this is the correct section, so please feel free to move it needed.

I know the basic consent is that a TRUE macro lens does 1:1 ratio.

The question I've got is regarding the 1:1. Is the 1:1 based on 35mm film size, or is it not relevant to film / sensor size. I was talking with my Dad, and we were trying to determine if 1:1 on my *istD was the same as 1:1 on his micro 4:3 sensor, and basically we just got confused.

Can anyone shed some light on this? I know 1:1 has been discussed, but I don't remember seeing any threads on if the sensor size has anything to do with the 1:1 / lens combination.

11-03-2009, 05:10 PM   #2
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1:1 is 1:1. It has nothing to do with sensor size, other than a small sensor will show less than a large sensor because it is smaller.
If an object is photographed at 1:1, it is the same size on the film or sensor as it is in real life.
On a 35mm film camera, this means that something that is 24x36mm will fill the fame, on a Pentax 6x7 something that is ~55x65mm (I don't recall the exact size of the 6x7 frame) will fill the frame.
On a Pentax DSLR, something that is ~17x25mm (again, I don't recall the exact sensor dimensions so feel free to insert the correct numbers in place of mine) will fill the frame.
11-03-2009, 07:04 PM   #3
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Right. 1:1 is 1:1 whether talking about APS-C or FF, just like 50mm is always 50mm. But because of the crop, a picture taken with a 50mm lens on APS-C *looks* different than it does on FF, and similarly, a picture taken at 1:1 magnifications also looks different between APS-C and FF because of the crop.
11-04-2009, 05:19 AM   #4
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So basically if you've got a bug that is the size of 35mm film, and you take a 1:1 picture of the same bug on my camera at 1:1, then you wouldn't see the entire bug, you would perhaps be missing some of his legs, or head, because he's a bit larger than the sensor. Does that make sense?

11-04-2009, 06:12 AM   #5
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Precisely.
Your canoe is in the mail.
11-04-2009, 06:52 AM   #6
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QuoteOriginally posted by eccs19 Quote
So basically if you've got a bug that is the size of 35mm film, and you take a 1:1 picture of the same bug on my camera at 1:1, then you wouldn't see the entire bug, you would perhaps be missing some of his legs, or head, because he's a bit larger than the sensor. Does that make sense?
so, that makes me wonder given the ability these days for software manipulation of a image when using a digital camera does the magic 1:1 really matter?
if you have used a low ISO, and been lucky enough to get that elusive perfectly focused image you can crop and enlarge way past the point of 1:1, is that not so?
and; if that is so, then why do we need ,for lets say insect photos, to go to the expense of buying a"macro" lens? surely a really good quality zoom or prime that allowed you to capture that sharp and focused image with a decent DOF wold be same given the comment on software?
Heresy this might be to some I know but I just keep wondering about this?
Alistair
11-04-2009, 08:20 AM   #7
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QuoteOriginally posted by adwb Quote
so, that makes me wonder given the ability these days for software manipulation of a image when using a digital camera does the magic 1:1 really matter?
if you have used a low ISO, and been lucky enough to get that elusive perfectly focused image you can crop and enlarge way past the point of 1:1, is that not so?
and; if that is so, then why do we need ,for lets say insect photos, to go to the expense of buying a"macro" lens? surely a really good quality zoom or prime that allowed you to capture that sharp and focused image with a decent DOF wold be same given the comment on software?
Heresy this might be to some I know but I just keep wondering about this?
Alistair
Well, not really! Whenever you start cropping an image you lose resolution ...not a problem if you are only making small images or shots for the web at 72dpi. However, if you are looking to make a print, even say at 8X10, you will notice the degraded image.

It always pays to frame your shot as close as you can in camera. Try to crop for composition and aspect ratio only.
11-04-2009, 08:26 AM   #8
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The problem is with the proliferation of cheap digicams with small sensors macro was redefined to mean photographing small things so a small sensor cam may shoot a tiny bug which would require 1:1 on a DSLR yet it's more like 1:5 in the digicam so technically it's far from macro. Yet it looks like macro (with actually better dof) and the manufacturer tells us the digicam does macro so we think its macro...

11-04-2009, 09:32 AM   #9
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QuoteOriginally posted by adwb Quote
so, that makes me wonder given the ability these days for software manipulation of a image when using a digital camera does the magic 1:1 really matter?
if you have used a low ISO, and been lucky enough to get that elusive perfectly focused image you can crop and enlarge way past the point of 1:1, is that not so?
and; if that is so, then why do we need ,for lets say insect photos, to go to the expense of buying a"macro" lens? surely a really good quality zoom or prime that allowed you to capture that sharp and focused image with a decent DOF wold be same given the comment on software?
Heresy this might be to some I know but I just keep wondering about this?
Alistair

There is a logical optics reason to differentiate Macro photography; the way photographs change with physical parameters like distance from the lens is different for Macro photography compared to "normal" photography.

The mathematical relationships are usually written in terms of the magnification, m, although they might just as well be written in other terms like the subject's distance from the lens measured in focal lengths.

Here's three practical examples:

Light intensity on the sensor (hence exposure time) depends only on F-stop for far subjects, but on both F-stop *and* magnification for macro subjects.

Relative Depth of field depends on both F-stop *and* magnification for far subjects but only on F-stop for macro subjects.

Image smearing by small camera rotations changes only with F-stop for far subjects but on both F-stop *and* magnification for macro subjects.

In an age of automatic cameras these distinctions are not very important for casual photography because the camera hides such details*, but such details are important for critical work where advance planning is needed.

The furious language wars that rage over terminology that is hinged on technical detail seem silly at times. Consider the usage wars raging over the use of "Gay Marriage" and "Civil Union" to describe the same thing (except for a few details.)

Dave in Iowa

* these days, the photographer seldom needs to make a decision about how to adjust exposure time when moving closer to a subject - the camera automatically adjusts if needed.
11-04-2009, 09:49 AM   #10
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Macro is defined loosely as a lens that is capable of focusing very close and for much of the time that works very well. A true 1:1 macro lens is usually much better made, is very sharp from corner to corner, little or no distortion, will have a longer focus throw for getting exact focus and obviously will cost more. Whether or not it matters is what you are using it for. For my uses, a close focusing lens is all I really need. For real precise, sharp close ups of small objects, the true 1:1 macro will do a much better job.
11-04-2009, 10:22 AM   #11
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QuoteOriginally posted by adwb Quote
so, that makes me wonder given the ability these days for software manipulation of a image when using a digital camera does the magic 1:1 really matter?
Well, it was always just an arbitrary number. It's just *more* arbitrary now.

I mean, really, what should it matter exactly how big of a bug you can fill a piece of 35mm film with? What really matters is that you can get that bug big enough and with enough resolution to make a good print. With film, cropping as a means of making an object look larger in a print was possible but not something the average person could do in their own living room. So it made sense to be sure to get the thing as big in the frame as you wanted it in the print. Someone arbitrarily decided that 35mm was the magic size of bug that should be able to fill the frame in order to call a lens "macro". And that of course works out to a 1:1 magnification ratio (OK, they more likely arbitrarily picked 1:1 as the magic magnification ratio, and that worked out to mean a 35mm bug was the smallest you could fill the frame with).

By that same logic, then, you really only need 1:1.5 magnification on APS-C to get a 35mm bug to fill the frame. So for most practical purposes, 1:1.5 on APS-C is as good as 1:1 was on 35mm. And since cropping is so much easier on digital, you don't even need a 1:1.5 lens to get those results. Of course, when you crop, you lose resolution, so how much you can crop will come down to how big you print, and how much resolution you need. Hard to compare between film and digital here, but realistically, with a 10-14MP camera, you can probably crop down by another 1.5X - 2X and still get 8x12" prints you'd have a hard time differentiating from film, in terms of resolution.

So no, I don't think you're wrong at all. I'd say even with just a 1:3 lens (like the kit lens!) on a 14MP camera, by simply cropping you could get results that were all but indistinguishable from images made with a 1:1 macro lens at print sizes up to 8x12" or so.

Of course, most 1:1 macro lenses are sharper than the kit lens, and they have a flatter field of focus, so it's not like there aren't advantages to macro lenses. But in terms of basic magnification and how it relates to resolution, you're seeing clearly.
11-05-2009, 02:54 AM   #12
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Marc, thats what I thought, so now perhaps instead of saving for a very very expensive macro lens, one can just save for a good prime of a reasonable focal length that will allow you to get a initial large image of the insect but will not have you right on top of it and of course give you a decent DOF.

I have question in a new thread about decent prime recomendations https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/78912-best-non...close-ups.html
Alistair

Last edited by adwb; 11-05-2009 at 03:24 AM.
11-05-2009, 05:16 AM   #13
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I've got a close up screw mount lens that isn't 1:1, but it's 1:2, and I think it does a fantastic job. Here's the link to the reviews.

Pentax Lens Review Database - 100mm F4 Macro

QuoteOriginally posted by adwb Quote
Marc, thats what I thought, so now perhaps instead of saving for a very very expensive macro lens, one can just save for a good prime of a reasonable focal length that will allow you to get a initial large image of the insect but will not have you right on top of it and of course give you a decent DOF.

I have question in a new thread about decent prime recomendations https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/78912-best-non...close-ups.html
Alistair
11-05-2009, 05:39 AM   #14
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QuoteOriginally posted by adwb Quote
Marc, thats what I thought, so now perhaps instead of saving for a very very expensive macro lens, one can just save for a good prime of a reasonable focal length that will allow you to get a initial large image of the insect but will not have you right on top of it and of course give you a decent DOF.

I have question in a new thread about decent prime recomendations https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/78912-best-non...close-ups.html
Alistair
I'm afraid you'll discover that it isn't practical to substitute large enlargement for how far the lens is from the sensor. As enlargement increases, contrast decreases.

The most cost effective way by far to achieve high quality macros is to use $10USD delivered extension tubes and a reasonably good manual lens (maybe $35USD).

On the other hand, used high quality macro lenses are not all that expensive, less than $100USD.
11-05-2009, 06:45 AM   #15
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QuoteOriginally posted by Marc Sabatella Quote
Well, it was always just an arbitrary number. It's just *more* arbitrary now.

As with the standard lens thing, you are missing the point of terminology.
We have terminology with relatively fixed meanings to aid communication. Shoot down definitions at your whim, call them arbitrary if you like, but these definitions are required for the purpose of ease of communication.
As an example, there is a product made from milk. Someone arbitrarily decided to call it cheese.
If you want to call it an apple, that's fine, whatever floats your boat, but don't expect anyone to figure out what you mean, since your just as arbitrary definition is nonsense, as is your lack of willingness to define things in fairly solid terms.

BTW, growing up in the photo business, I was taught that the term macro was a fairly loose definition that meant focusing closer than what a normal lens would do, but 1:2 was considered minimum performance for a lens to be a macro.
The zoom lenses of the 80s moved the bar somewhat and the definition became 1:4 for many people, especially those in sales. The more technically minded of us called them close focus lenses to differentiate them from true macros.
This hasn't changed. What has changed is the technology that gives us the final image.
Technically, if a sensor is 1/2 of an inch across, then for a lens mounted to it to be defined as a macro, it would have to be able to focus on and allow a frame filling picture of something in the range of 1/2 into to 1 inch long, be it a bug, or a cigarette butt or anything else.
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