'macro' as 'more detail than unaided eyes'

[rjlittlefield]

If you've been reading my ramblings for very long, you know that I'm not a devout fan of the concept that "macro" ought to mean 1:1 or greater lens magnification. (There's a discussion of why, in this topic.)

Recently I was reminded of what one of the classic books on the subject had to say.

Fundamentally, a photomacrographic subject is one that would be visually examined with a loupe or with a hand lens.

Of course, the reason one uses a loupe or hand lens is to see more than the unaided eye can see.

This led me to propose an alternate definition:

Shooting "macro" means taking pictures that show more detail than unaided eyes could see in the real subject.

Reasoning forward from that simple concept, I worked through some math that ended up saying

Now we've got a numeric criterion: a digital image is "macro" if it has at least 12-24 useful pixels per mm of subject size. Using our forum's limit of 800 pixels, anything under 33 mm field width is definitely macro, anything over 66 mm could only be close-up, and stuff in the middle is ambiguous depending on how sharply it's rendered.

Tonight I took some time to test experimentally whether the concept and calculations seemed to be on the right track.

The experiment seemed simple: find a suitable resolution target, look at with my unaided eyes, shoot it with a few different camera & lens setups, and see how the results track the predictions.

Of course, the experiment ended up being more complicated than I had hoped. The problem was to find a suitable target. I needed something with small detail having a good range of size. A tiny eye chart would have been ideal, but I didn't have any such lying around. For a while I contemplated firing up the old darkroom and printing one, but that seemed like way too much trouble. Finally it occurred to me that I didn't really need a printed tiny eye chart -- one projected onto a matte screen or even just focused in the air would work fine.

I fired up Word, typed in a bunch of different text lines sized from 40-point font down to 4-point, printed them using a high quality inkjet, then set up an old camera lens to project a 1/10th size image to use as a test target. So, the test target was essentially tiny text, from 4 points down to 0.4 point.

Here's what the setup looked like:


On direct inspection, it turned out that I could just barely read the line labeled "20 point" (actually 2 point!) using my normal reading glasses. With a different set of glasses that I use for hobby work, it was more like "17 point" (actually 1.7).

Then I shot the target with three camera & lens setups:

• Canon 300D with a Sigma 105 macro lens at 1:1, producing a field width of 22.7 mm,
• Canon SD700 IS at approximately closest focus, with a field width somewhat over 27 mm (I'm not sure exactly what the autofocus did), and
• Canon 300D with a Sigma 18-125mm "macro focusing" zoom, at minimum field width 101 mm.

I resized each of the resulting images to 800 pixels and asked the question, "What can I see in the pictures?"

The results are shown below, and I'm happy to see that they agree pretty closely with predictions. At 800 pixels, the 22.7 mm field of the macro lens at 1:1 reveals something like 3 times finer detail than I could see with just my eyes. The SD700 point-and-shoot also reveals considerably more detail than just my eyes, though not as much as the 1:1 macro on the 300D. And the not-really-a-macro zoom lens falls short of showing even as much as my unaided eyes can see.



This approach feels right to me -- characterize a photo as "macro" or not based on the amount of detail that it shows.

I'd be interested in other people's thoughts. Comments?

Thanks,
--Rik

[georgedingwall]

Hi Rik,

Your experiment cetainly seems to show some interesting results.

A few questions.

When you use "Pixels" as a criterion for useful pixels per mm, does it matter what size the original pixel was. My D70 and D200 both have approximately the same size sensor, but the D70 is 3008 pixels wide, while the D200 is 3872 pixels wide. This must have some effect on any calcualtion which uses pixels per mm.

When viewing by eye, were you viewing from you own closest point of focus? Does the closest point of focus vary for each individual. If it does, then wouldn't this still allow for uncertainty as to the boundary between macro and close-up.

How would you allow for the variation in the seeing ability in the human eye. I recall from the days when I did a bit of astronomy, that there were people who could see more detail in the night sky than I could, while there were also people who could see less detail.

If you are going to use your quote ;

Shooting "macro" means taking pictures that show more detail than unaided eyes could see in the real subject.

Then surely the naked eye viewing distance, and the variation in seeing ability, are variables and not constants. as the amount of detail that any individual can see is going to be unique to the observer.

If we are to get to a useful definition of macro, then surely it must be free of any variables such as pixel size and the differences in the viewing abilities of the observer.

I don't really have any fixed view of what macro or close-up should be. I don't think it is unreasonable to use 1:1 on the sensor of a 35mm style DSLR as a boundary point between macro and close-up.

If I was asked what kind of photography I like to do most, I would almost certainly reply "Close-up". Your definition, quoted above, seems to me to also be a good definition of close-up photography. I just like to get close to things so that I can see details that are not normally visible to my eyes.

I think it is going to be difficult to come up with an objective definition of Macro and Close-up. The only problem I have with the misuse of the Macro term is when equipment makers claim that a camera has a macro mode which turns out to be "Just a little bit closer" mode, as you found with your Sigma 18-125mm "macro focusing" zoom.

Good luck on your continuing quest. Bye for now.

[Epidic]

The problem is I can take a landscape photograph that shows more than the human eye, but is it "macro"? Alternately, in a three-dimentional space I can see more detail in a subject simply because I am not fettered by depth of field.

I admire your attempt at trying to make an objective definition of the term "marco." The problem is that it is a subjective term. Even basing it on magnifiction, which is the easiest way, it is a fuzzy area - if 1x is macro, than is .99x not? What about 0.9x? Where do you draw a line? Can the line be anything but subjective? I think "macro" is like the definition once declared about pornography, I know it when I see it.

Sorry to be such a wet blanket.

[DaveW]

The original English foot measure was based on the size of a king’s foot in order to standardise it as the population at large had various sizes of feet. The meter I believe was originally a proportion of the distance around the equator, another attempt at standardisation. I used to be able to read minute print with my naked eyes; I now need reading glasses to see the text on this computer screen in front of me. If you are going to use resolution greater than the human eye as a standard for Macro you will first have to get international agreement on what is the resolution of an average human eye!

As I pointed out before, in science the law of priority usually applies. Therefore it is the original coiner of the term that defines it forever. If a later worker wishes to use different criteria they need to invent their own terminology, not try and modify the original authors to indicate something they did not originally mean.

It would be interesting to consult the full sized Oxford English Dictionary to see if the terms "Macrophotography" and "Photomacrography along with "Microphotography" and "Photomicrography" are defined there and who first coined them.

There was a program recently on British TV where the OED asked for details of new words for inclusion in its updated edition. The criteria for a word to be accepted was that it must be in general usage, meaning it must appear in print more than a certain number of times, plus listing the earliest example that can be found of it appearing in print, with if possible the authors original meaning.

Also, what is close-up photography? Is it when the lens is not very far from the subject, or merely image magnification? Obviously I am close-up when I take an image at a large magnification with my 60mm micro nikkor. But what if I take the same sized image with a 1000mm or even a 1500mm telephoto from across the road, I am hardly close-up then?

In botany a name is merely a handle to identify a plant, it does not have to be appropriate. It simply defines what the original author intended it to mean. It was pointed out that there is a plant having a specific name "clusifolious". Clusius was a botanist and folious means leaves. Therefore we have the inappropriate name that the plant has leaves like a botanist!

As I pointed out earlier the term "Photography" meaning "writing with light" is not as appropriate as "imaging with light" would be, but I cannot see a great clamour to change this because we all accept what it means as defined by it's originator.

DaveW

[rjlittlefield]

Excellent feedback, guys -- many thanks! I was hoping to hear from some other nay-sayers, but I'll take what I can get.

Epidic, I don't see your comments as being a wet blanket. I agree completely that "macro" is a fuzzy concept, and I'm not really trying to make it more precise.

What I am trying to do is tease out what are the various aspects that people consider important.

To me, defining macro as 1:1 or greater lens magnification seems like defining "overweight" as meaning 215 pounds or more. It's objective, it's precise, and it's extremely relevant --- in a few situations, like say if you're making safety harnesses or hang gliders. But somehow 215 pounds doesn't capture the essential features of "overweight" nearly as well as something based on body mass index or percent body fat.

DaveW, I made a trip to the library today. Appearing below are the OED sections for "photomacrography", "macrophotography", "photomicrography", and "microphotography". Perhaps you will read these differently, but to my eye they don't lend much support to the otherwise admirable approach that you'd like to take. It appears that the first author to use "photomacrography" did not really define the term. The definition seems to have evolved over a period of time, with some 30 years between first use of the word and first occurrence of "natural size on the film".

Even worse, it turns out that the Oxford English Dictionary (2nd edition, 1989), does not even distinguish between "photomacrography" and "macrophotography"! In fact, the first non-phonetic symbols appearing after "photomacrography" are "=MACROPHOTOGRAPHY". It appears that the earliest authors may indeed have intended "macrophotography" to refer to extreme enlargements of a small negative, but according to the OED entry, by 1940 the two terms were used as synonyms.

It's probably important to point out that the Oxford English Dictionary is a dictionary of English, not a dictionary of specialized Jargon as it might be used in a small technical community. It's not unusual for English and Jargon to use the same words in quite different ways. Inevitably, you have to decide which one to speak, or even better, to point out the difference so that readers in both camps will understand.

By the way, the situation is entirely different for "photomicrography" and "microphotography". In that case, the first user of "microphotograph" did precisely define the term and actively defended it from later confusion. Those two terms are clearly separated in English as well as Jargon.




Images courtesy Oxford English Dictionary, 2nd edition, 1989. Reproduced here under the "fair use" copyright doctrine.

georgedingwall, thanks for your questions and comments -- thoughtful and careful as always.

You are exactly correct that at same lens magnification, your two cameras will have around 25% different pixels per mm at the subject. In fact, given a sufficiently sharp lens, the D200 at 3872 pixels will capture 25% finer detail than the D70 at 3008 pixels.

It's entirely your choice how to exploit that. You can shoot the same field width and pick up finer detail, or you can use lower lens magnification and shoot a wider field at same detail, or you can compromise between the two.

What the "unaided eye" criterion cares about, is how much detail is visible in the image, as presented to the viewer. A system (lens+sensor+software+display) will be "macro" to a greater or lesser extent depending on whether it shows a lot more detail, or only a little more detail, than the unaided eye could see in the real subject. (Previous assumptions now stated: that's at minimum viewing distance, in the most favorable illumination, for a person with average "normal" vision.)

You're also correct that I've glossed over differences between individual people. I don't consider that a problem. If we can agree that the concept is correct, then it's easy to create a standardized measure. Actually, that was already done, years ago, by the people who decided what 20/20 vision means, and that the power of a hand lens would be 10"/FocalLength.

There's another issue that I haven't noticed anybody raising. Under the "unaided eye" criterion, a single .JPG can produce both macro and non-macro images, depending on how it's rendered. For example, my "big beetle, small beetle" picture is clearly macro (despite having been shot at 1:1.5 and cropped ), because at 60 pixels per mm on the subject, it shows 5 times finer detail than a standard unaided eye could see. Consider, however, the same .JPG reproduced in a smaller size:



Is this picture "macro"? I'll argue that it's absolutely not! The detail shown in this smaller image is only 6 pixels per mm -- about half of a standard eye's. It's a thumbnail of a macro image, to be sure, but it's not a macro image itself, no matter what lens magnification it might have been shot at.

In reviewing the literature, I see three essentially different facets of this word "macro":

• Showing what you would see through a hand lens or a loupe, that is, several times finer detail than the unaided eye.
• Requiring equipment that's somehow more complicated, unusual, or difficult to handle than sticking a closeup lens in front of an ordinary camera.
• Operating at 1:1 or greater lens magnification.

Are there others?

--Rik

[rjlittlefield]

Well, I'm a bit disappointed to find no responses to my previous post.

But that's OK, let me push forward a bit on my own and see where this line of investigation goes.

In an earlier post, I evaluated three systems (lens/camera/software/display) against the "unaided eye" criterion. I observed that two of them showed significantly more detail than the unaided eye could see, while the third did not.

Is that the end of the story? Of course not, or I wouldn't be writing this.

In my earlier post, I resized all images so that full frame would be 800 pixels wide, a reasonable size for web display and currently the forum limit.

What happens if I sacrifice full frame, and instead crop the images to show a smaller subject in the same 800 pixel display?

Here's the result for two lens setups that are interesting to consider.



In my earlier post, the Sigma 18-125 zoom failed to equal the unaided eye. But that was with full frame, 101 mm wide, resized to 800 pixels.

By cropping to much less than full frame, and resizing in proportion to the crop, the story changes.

We now see that the cropped/resized Sigma 18-125 image shows something like 2X finer detail than the unaided eye, over a subject size of 39 mm displayed in 800 pixels. (Cropping tighter and resizing to 800 pixels just gives "empty magnification", exposing no further detail.)

So, under the "unaided eye" criterion, this new system (same lens & camera, different handling of the image file) now produces a legitimately "macro" image -- it's showing detail that the eye would require a 2X hand lens to see.

To repeat: the Sigma 18-125 can shoot at the scale of a 2X hand lens under some conditions, say, with a 39 mm subject displayed in 800 pixels.

Does that mean it's good for shooting at this scale?

Nope. Actually, it's pretty awful.

One reason why is not immediately obvious until you run the experiment, and then it clubs you over the head. The problem is focusing.

Using the Sigma 18-125, that 39mm subject occupies less than half the width of the viewfinder. That makes it so small in the viewfinder that the poor photographer can't really tell whether the subject is focused or not. (Trust me on this -- you're seeing the best of a fairly long series.)

In contrast, using the Sigma 105 at 1:1.74, the same 39 mm subject is full-frame -- a lot easier to deal with!

A second issue is available detail. Using the Sigma 105 lens designed for macro, and blowing that 39 mm up to full frame, the camera captures a lot more detail in the same subject than it does with the Sigma 18-125, cropping 39 mm out of the middle of the frame. That extra detail is barely visible at 800 pixels. We have to display a lot larger image, or a smaller crop, to make it obvious. But it's there if we want it. You can see in the pictures that the 105 captures over twice as much detail as the 18-125, for the same 39 mm subject. (Though not as much as it can capture for an even smaller subject, at 1:1.)

Mostly what I'm doing here is trying to clarify the issues and figure out how to explain them.

Clearly the Sigma 18-125 is not as good at macro as the Sigma 105 that's designed for the job. The 18-125 can produce legitimately macro images (under the "unaided eye" criterion), but only under pretty restricted circumstances. Even there, it's a pain to use. In contrast, the 105 is a lot easier to use and captures more detail in the same subject.

If there's a bottom line for this post, it's simple: decide what size subject you want to image, and choose a lens that can make that subject fill the frame. It'll be easier to work with and you'll capture more detail, which leaves more options open.

Comments?

--Rik

[DaveW]

Reason for no reply yet Rik is I have been out a couple of nights so have not had time to wade through all the stuff on this thread. I will read it up and try and understand it when I get more time!

DaveW

[Epidic]

Rick, I have a feeling you are making this more complicated than it is. But this seems to sum up the problem for me:

decide what size subject you want to image, and choose a lens that can make that subject fill the frame.

I think you hit the nail on the head.

[Epidic]

To me, defining macro as 1:1 or greater lens magnification seems like defining "overweight" as meaning 215 pounds or more. It's objective, it's precise, and it's extremely relevant --- in a few situations, like say if you're making safety harnesses or hang gliders. But somehow 215 pounds doesn't capture the essential features of "overweight" nearly as well as something based on body mass index or percent body fat.
--Rik

I understand the limits of using magnification. Just think of a 1:1 "macro" image taken with an APS size CCD and an 8x10 view camera. They don't look the same.

I am not really into the resolving power criteria. It never mattered with film, why start now with digital. I guess the best compromise would be angle of view, which is what your "use the lens that fits the subject to the frame" statement is. The trouble with the angle of view is magnifiction is not a factor and it would apply to an object at 5mm as well as to one at infinity. So I guess there needs to be a relationship between magnification and angle of view. But that just seems complicated. If I know the magnification and format size, it is fairly straight forward to calculate what object dimensions are going to fit in the frame. Naturally, we still have the problem of what "macro" actually is. Even with a magnification/angle of view scale, where are you going to draw the line to define "macro"?

BTW, I believe the Focal Encyclopedia of Photography has a good definition. Unfortunatley I can't get to my copy.

[rjlittlefield]

I believe the Focal Encyclopedia of Photography has a good definition.

If you find that definition, please let me know what it says. I'll be very interested to see whether it's some version of what I've already identified, or something else entirely.

resolving power criteria...never mattered with film

I question that statement. I'd wager that it's been implicit in people's thinking, but they've just never happened to put it in those terms.

Until very recently, I never spoke in terms of the unaided eye criterion either. But thinking back over the last 40 years that I've been doing photomacrography, I realize that I've used it over and over again. Even when I went to buy binoculars for butterfly watching, I took a butterfly with me. Want to guess what the criterion for "good" ended up being? It was when I could see finer detail through the binoculars at their closest focusing distance, than I could see with my own eyes at their's. Same thing for photography. The natural breakpoint was always when I could capture on film -- and implicitly, show to a viewer -- more detail than he or she could see in person.

I guess the best compromise would be angle of view, which is what your "use the lens that fits the subject to the frame" statement is. The trouble with the angle of view is magnifiction is not a factor and it would apply to an object at 5mm as well as to one at infinity. So I guess there needs to be a relationship between magnification and angle of view. But that just seems complicated.

I think that now you're the one who's making things more complicated than they are!

Why involve criteria that cannot be discerned in the photo, while rejecting a simple and intuitive criterion that can?

It's simple -- how much detail can you see in the image? If you can see more in the image than you could in the subject, then call the photo "macro".

If you'd like, we can quibble about whether the magic number should be same detail, or twice as much detail, or some other amount. Twice as much would be nice -- that's about the lowest power hand lens that anybody would bother to use. I really don't care where the line is, because it's a fuzzy line in any case. My major concern here is to understand the form of the criterion.

As I wrote earlier, I see in the literature three forms:

• Showing what you would see through a hand lens or a loupe, that is, several times finer detail than the unaided eye.
• Requiring equipment that's somehow more complicated, unusual, or difficult to handle than sticking a closeup lens in front of an ordinary camera.
• Operating at 1:1 or greater lens magnification.

Really, all I've done is to slightly formalize Kodak's definition: "Fundamentally, a photomacrographic subject is one that would be visually examined with a loupe or with a hand lens. "

Tell me again, what's wrong with that?

--Rik

[Epidic]

As I wrote earlier, I see in the literature three forms:
Showing what you would see through a hand lens or a loupe, that is, several times finer detail than the unaided eye.
Requiring equipment that's somehow more complicated, unusual, or difficult to handle than sticking a closeup lens in front of an ordinary camera.
Operating at 1:1 or greater lens magnification.
Really, all I've done is to slightly formalize Kodak's definition: "Fundamentally, a photomacrographic subject is one that would be visually examined with a loupe or with a hand lens. "

Tell me again, what's wrong with that?

It is too subjective. I also feel it is arbitary.

In your first criteria, what is "detail"? ("Detail" is a subjective term unlike angular resolution and resolving power which can be measured. And detail does not mean the same thing as the other two. How do you separate detail from sharpness?) How can you determine and define "several times"? How do you correlate what you can see through a loupe to what a camera sees - DOF alone makes that a difficult criteria. Any reference from an imaging system to human sight is alway an approximation.

Your second criteria is also subjective. I can take a standard pictorial lens and extend the bellows on my veiw camera to take a "macro" image. There is no special equipment needed. Why can't I use a supplimentary lens? It is a perfectly valid way of shifting the object plane?

The third criteria is simply a guideline. Are you going to say at .99x it is no longer "macro"? What about .9x? When does "macro" become "micro." And is your 1:1 only at the image plane? What if I shoot at 0.5x and enlarge the image so it is larger than 1:1? That image is not "macro" even though it is larger than 1x? 35mm shooters are very confused by 4x5 pictures taken at 1x - they don't think they are "macro."

Perhaps I am tainted by my education. But I learnt that the terms "macro" and "micro" were subjective and the criteria were just fuzzy guidelines. The Kodak definition is vague because the concept is vague. There are just too many ways an image can be made and judged. I find the terms "macro," "mirco," and "close-up" add nothing to an image I am viewing. Neither do they change the way I work. I see no practical reason for changing the Kodak definition.

I will post the definition in the Focal Encyclopedia when my copy gets here.

[DaveW]

What people prefer are "Go, No Go guages". That is the object either fits and goes through or it does not. Macro meaning 1:1 or above on the film or sensor is such a "guage", either it is or it is not! 1X + qualifies but 0.99999999 add infinitum X does not!

Maybe illogical but useable!

DaveW

[rjlittlefield]

Will,

Play a game with me, please.

Pretend that I have never seen a hand lens or loupe, and I have no idea why I might want to use one.

Kodak tells me that "Fundamentally, a photomacrographic subject is one that would be visually examined with a loupe or with a hand lens."

But that doesn't mean anything to me, because (we're pretending) I don't know about loupes and hand lenses.

Can you help me out?

Please explain to me, using other words, the concept that Kodak is trying to communicate.

Thanks!
--Rik

[Epidic]

Sure, I will play.

A loupe is a small optical instrument that allows you to see small objects better. Photomacrography is the photography of small objects.

This better be good or we are going to discuss whether knowledge is apriori as well as Kant and the catagories of reason.

[rjlittlefield]

A loupe is a small optical instrument that allows you to see small objects better. Photomacrography is the photography of small objects.

This better be good or we are going to discuss whether knowledge is apriori as well as Kant and the catagories of reason.

No, I don't want to go that far -- I never could Kant.

The reason I asked the question is because I thought you would have to reply as you did: "to see small objects better".

Better than what? Better than the unaided eye, I presume.

So I claim that Kodak's definition implicitly includes the concept that the photomacrograph should reveal more detail than the unaided eye would see in the original subject.

If it doesn't, then why did they choose to describe the subject in that way?

--Rik