My travel into reflex photography continues, more and more interesting and fun

I have some basic questions, or some I belive are such for anybody with little experience, and yet I could never find clear answers so far.

I understand that a "macro" lens is supposed to "uncover details that would be impossible to detect by the eye and give new perspective to extremely minute subjects"(c) Canon.
That is, they are more detail-oriented lenses than non-macro ones.

But, what does it mean, precisely?

To be more specific:

1. What is the difference between a
Canon EF 50mm f/2.5 Macro
and a similar (to me :)) fixed focal length lens such as
Canon EF 50mm f/1.8 (other than the aperture?)

2. Why would you chose a 100mm Macro lens over a 50mm Macro lens? Or vice versa?

3. By reading the minimum focusing distance, it seems to me that all reflex macro lenses have pretty high values (20-30 cm) compared to compact cameras (which I've often placed at 10cm or less from subjects). Interesting. No answer needed here. Just thinking our loud

4. Do you want a low f/ in a Macro, or not? Or, what range would you, ideally want? It would seem to me that being able to properly adjust DOF is crucial in macro photography, as with such small subjects you may have to be quite accurate in deciding what to focus and what to blur, am I correct?

5. Why on Earth is it called "Macro" photography?! All that I know in every discipline tells me it should be called "Micro" photography , but ok, that's the convention, I suppose.

So, thanks everyone for sharing your knowledge and thoughts.

You certainly could get a set of "macro extension tubes" for your 50mm and it would then be able to generate increased magnification. At that point, the difference between a hacked 50mm with macro tubes and a 100mm is that you have the zoom difference, i.e., how close you need to be to the target to take a picture at a given level of magnification.

So, essentially one would prefer a 100mm macro lens over a 50mm macro lens because of the practical advantage of obtaining the same level of magnification by being more far away from the subject, in all those occasions when this is beneficial (e.g: macro of insects).

But, what is the difference between a 50mm macro and a 50mm non-macro lens? Is that difference the reason why you're saying I could get an extension tube if I had a "standard" 50mm (which I actually don't)? Wouldn't the extension just change the focal lentgh?

A macro lens is generally a lens that is capable of resolving at least a 1:1 reproduction. It doesn't have anything to do with the focal length of the product. Though some will argue that it's 1:2 or even 1:4.

Macro lenses also allow close (or very very close) focusing distances, something not possible with an equivalent focal length non-macro lens.

When you're looking at different lenses make sure you look at the practical focusing distance because how close you get is going to make a big difference with the magnification. Also, with some subjects you can get super close (within a couple of inches or less) and with others you won't have that opportunity. Here a longer focal length is going to help you. Also of note is the depth of field you'll achieve with different combinations of lenses and accessories. I've played around with some reversed lenses with only a few millimeters of focus. You can make some interesting shots, but even on something as small as a fly, you'd probably only get part of it n focus.

The Canon EF-S 60mm macro lens I have here, can definitely focus very close to the subject -- about 9cm according to my measuring tape.

That's pretty good, though my old Nikon E990 "compact" digital could get within 2cm.

I think the idea of a macro lens, is that it is one which produces 1:1 or better magnification. The distance isn't important for that, though it is important for other reasons.

Macro lenses also tend to have a longer focus mechanism -- it takes more turns of the focus ring to make large adjustments. This allows for much more precision in focussing, given the extremely short depth-of-field at close distances.

Cheers

I always want a low f/, because it helps focussing -- both automatic and manual focus benefit from more light being available. But often, one wants f8-f11 for the actual shot, to get sufficient depth of field. Not always, but often.

Which is why flash photography goes hand in hand with macro photography -- the flash is needed to compensate for the tiny aperture (which lets in very little light).


Dunno -- because it makes things look BIG! (?)

As for distance from the subject -- I nearly always want to be CLOSE to the subject. Less distance means less motion blur from camera shake.

That's for practical (hand-held) photography, not studio (tripod) stuff.

Cheers

Mark raises an interesting point, lighting is the key to great macro photography.

In fact getting too close can sometime actually cause problems by casting your own shadow on your subject, hence the advantage of using a 100mm lens over a 50mm to allow yourself to get a little further away.

I personally use macro tubes, but every time I use them I lust after Canon's 100mm (or even 135mm) Macro lenses. Just yesterday I was taking a picture of wedding rings and thought I'd really like a proper macro one day. The tubes take a little bit of light away from you, so you have to bump your exposure, it's not a lot but the more tubes you use the more you have to bump. Not ideal when you are shooting handheld macro

Many Macro photographers will set their focus manually then actually move the camera in and out a little for fine tuning, I tend to do this as well. I take my shots on a glass table usually (cool reflections of the rings!) I rest the front of the lens on the glass set my focus then simply slide the camera in and out until I'm happy with the shot, normally at f8 with a little help from some bounced flash.

Cheers

Cris

Thank you all... I am getting it, now, think.

Canon 50 mm f/ 1.2L, f/ 1.4 USM, f/ 1.8 II all have a longher minimum focusing distance than the Canon Macro Lenses, in fact.

Surprising, macro lenses from canon don't go below f/ 2.5, while non-macro ones go up to f/ 1.2 ...

As a side note, I am noticing that fixed focal length lenses (from Canon, but at this point I would expect the same from Nikon) are just as expensive as zoom lenses. I am surprised. I had assumed that zoom lenses would be more complex to build and produce, and therefore more expensive than fixed focal length...

The primary cost in a lens is the glass...

They don't need to. f2.8 is wide enough for good auto/manual focus, and the depth of field is about 5mm or so wide open (or so my measuring tape tells me).

On the other hand, the 60mm EF-S I have here goes as high as f32, for increased depth of field. And it's pretty darned sharp most of the way there.

Note that the 60mm is equivalent to 96mm on my Canon 40D, so it is effectively a 100mm macro lens.

As a point of trivia, Nikon use (for as long as I can remember) the word "Micro" to describe and brand their "Macro" lenses.

This will have more to do with the quality of the components used rather than how complex they are to build. Having said that the cheapest lens in the Canon range is a Prime.

Take the price difference between the 50mm f1.2 and f1.4, image quality between the two is marginal to be honest, but the 1.2 is just amazing to use and is built to last. On the other hand the f1.4 (which I have) is much lighter and won't last as long, it's all in the quality they do very much the same job when it comes to the photo itself.

Cheers

Cris

Again, thank you all. This is so very informative.

I decided to get myself a Speedlight for Christmas, but I am now also considering to get a macro lens for my gf. She got me into reflex photography, and she's been wanting a dedicated macro lens for a while.

I'd love to be able to get her the Canon 100mm L series, but it is very pricey. On the other hand, luckily enough, we both have a Canon body

Keep in mind that 100mm behaves like 160mm on most Canon bodies.

Yes, true.

I like the fact it is IS, also.

As always, there's a tradeoff. Let's say you're going for the same 1:1 reproduction ratio with both lenses (i.e., taking a picture of something the same size as your sensor). A 50mm macro will need to be significantly closer than a 100mm macro. Advantage goes to the 100mm. On the flip side, the 100mm will have less depth of field at the same aperture. Advantage goes to the 50mm. The longer lens will also tend to compress the differences in depth, giving you a "flatter" image, while the shorter lens will tend more to exaggerate things. Advantage (although it's really an artistic question) probably to the longer lens.

At the limit, many point-and-shoots have incredible macro capabilities. The lens is practically touching its subject when you're shooting at the closest. You can take hand-held macro shots of flowers without flash and with exceptional depth of field due the incredibly short focal length of the lens. The tradeoff is that you don't always want to get so close. How close exactly are you comfortable getting to that bee on a flower? Also, the lens casts its own shadow. (Although there's at least one Pentax point-and-shoot with LEDs in a ring around the lens to help with macro illumination.)

And, yes, there's really not much difference between a 50mm "standard" lens versus a 50mm "macro" lens, except that the macro lens is designed to rack itself further away from the camera body. That's what macro extension tubes are all about. Generally speaking, what really differentiates macro lenses is that they have exceptionally high quality optics but not necessarily the widest aperture.

I can use my old Zuiko 90mm f2 macro with my Olympus E410, it's great.

The Zeiss Luminars are the best macro lenses to use if you are interested in going higher than 1:1. They are older completely manual lenses specifically designed for use on a bellows and for greater than 1:1 magnification. Bellows are also useful in the macro world so you can do things like tilts and swings. Tilts and swings can help increase your depth of field without restoring to extremely high apertures which kills your image quality, due to diffraction. If you want to learn more about movements possible on a bellows read about the Scheimpflug principal not exactly light reading but interesting..

I have a small bellows unit, but it only supports extension/contraction... No tilt nor swing/shift unfortunately.

While I haven't made extensive use of it, it does make for some crazy closeups and allows for relatively easy adjustment of lens positioning once you've fixed your rig in place.

Thank you Dan. This is very useful!


And, I take this is a disadvantage because in order to increase DoF you need to decrease aperture and therefore you will need more light/longer exposure time, all else being constant. Am I correct? But, I suppose that sharpness or detail level will not be affected directly by this, as they mostly depend on the optics quality?


Ok, I see. So theoretically, at a given magnification level, a Macro lens will produce sharper / more detailed images than a "standard" lens, again holding all else constant: lens build quality, etc.

Yup, that's exactly the idea. Of course, when you're using a macro flash kit (e.g., a ring light or the Nikon R1C1 kit), guide numbers are largely irrelevant because you're so close to your subject. You can bring as much light to the party as you want. If you want to work with available light, however, this is a significant difference.


When you're buying a macro lens, you're paying for optical quality.


Pretty much, yeah. Or, if you prefer to think of it as what you get for a fixed pot of money, you're trading off a wider maximum aperture for increased sharpness and a focus knob that racks the lens out a bit further. (For what it's worth, according to Thom Hogan, vibration reduction doesn't have much impact when you're doing super-duper closeups, so you may be able to save money by buying a cheaper macro lens without it.)

Optical quality has little to do with it. The more you stop down your lenses the more optical quality you are losing to diffraction. It's a physical fact that no lens technology can solve. What you want is a lens that is going to be diffraction-limited at a certain aperture. That's the best you can hope for. If you look at lens tests you will see most high-quality lenses start getting the same lp/mm numbers as aperture goes up. That is the diffraction limit. Also it matters little if your lens is 50mm or 100mm at 1:1 and higher. Depth of field is basically the same in both cases: not good.

Just to avoid confusion, I realize I do need to make sure my terminology is somewhat accurate. By "optical quality" I referred to the capability of a lens to resolve details and produce sharp and crisp images. I wonder whether I am wrong in this?


Ok, yes, I understand the physics behind this.


Ok. So, speaking in theory, would there be a difference between a Macro and a non-Macro lens, in this specific regard, holding all else constant?

Would it be correct - I am just guessing here - to say that a macro lens would limit its max aperture in order to gain something in terms of little-diffraction at lower apertures, assuming little diffraction is what you want to obtain crisp and detailed macro pictures? In other words, I am supposing that If I want to build a lens that is very good for macro and therefore with as little diffraction as possible, I may have to limit the possible aperture available? For example, a Macro lens would be excellent at f/2.5 and really bad at f/1.8, so I have to limit it at f/2.5, while a non-macro lens is just good at f/2.5, but not bad at f/1.8, so I allow aperture f1.8?


Why is that? Not good in what way?

Again, thank you all guys. I am learning so much. This is just great!!

No your right that some lenses are better than others in terms of quality. What I meant was that at working macro apertures (higher f numbers) most lenses are diffraction-limited anyways. That is if you have two modern macro lenses and you stop them both down to f/22 or higher the most likely result is that both lenses will be diffraction limited and produce the same overall result. The same does not hold true at less extreme apertures like say f/8 where most lenses are at their optimium working apertures.



Yes. Macro lenses generally employ lens designs that allow them to work better at higher magnifications than general purpose lenses. This allows them to generate higher quality images in the macro world, especially at their optimum apertures.



Well diffraction comes into effect on the other side of the scale- the high f numbers. So you will find most lenses don't allow you to stop down the aperture past say f/22, even though it is mechanically possible to go higher they don't want you too because you will get unsharp results. Just for a historical aside, Edward Weston had one of his lenses modified to go to f/256, he then complained to Ansel Adams (in a letter) of unsharp results with the said lens. Ansel Adams then explainined that modifying lenses in such a way wasn't a good idea because of diffraction problems.

I'm not sure what effect the maximum aperture (lowest f number) has on lens design. Generally the faster the lens the harder it is to make though.




Simply put it's because if you take two lenses and frame a shot at the same magnification (in this case 1:1) then depth of field is identical. In other words the picture you setup with both lenses would be identical, same framing, same subject size, same aperture. So depth of field is also the same. The only thing that affects Depth of field in this case is the aperture you use and/or the Image Format (digital vs film, cropped digital vs full frame).

Oh, so I did not have the physics right in my mind, there. In any case, I understand.
So, This must be due to different refraction indexes of the various elements in the lens itself, I suppose.


Yes, that'd be nice to see some more in depth explanation on what exactly causes diffraction at low aperture. My (wrong) assumption before was that a greater aperture, the incidence of light rays would be such, especially at the edges of the lens, to create high diffraction, but clearly there's something more complex happening while rays cross the various components of the lens.


Oh right, I was assuming different focal length=>different aperture, but that's not necessarily the case. In other words, same aperture, same DoF regardless of the focal length...

Again, this is so good. Thanks all for the explanations!

The simple explanation of diffraction is that as light rays go through a small hole some of them get "caught" on the edges of the hole and bend around them and distort. Wikipedia can give a more technical explanation. That's why the smaller the hole (e.g. higher f number) the more diffraction effects you get.



Not quite. Same aperture + same magnification + same image format = same DoF. So a 50mm lens at 1:1 magnification has DoF equal to a 100mm lens at 1:1 magnification at the same aperture. So in Macro the choice of focal length only really affects working distance (100mm lens can be farther back from the subject at 1:1 mag. than 50mm).

Oh! Of course!
See, I'm actually familiar with diffraction, but did not think of it this way: so, is the hole at such low aperture value THAT small? Wow.
I see it now and indeed it makes sense.
See, diffraction can well be caused by change in refraction index from one medium to the other on the path of the light ray, and I assumed something similar was happening, maybe coupled with some change in the path of the light inside the lens body. Well, all very great to know!


Got it. Thanks!

So I made it. I bought a 100mm Macro L lens for my girlfriend for Christmas.
It is impressive. She was blown away and she can't stop taking macro pictures. Actually, I am having a lot of fun with it as well!

Thank you all for your help and explanations!

Here is a couple of pictures I took, which impressed me for how crisp they are.