Help a guy pick a camera lens?
June 29, 2010 12:21 PM   Subscribe

I'm in the market for a new camera lens. I'm attempting to do my "due diligence" - if I'm going to pony up and drop $500 - $600 on a lens, I want to make sure it's right - but a lot of this information doesn't make sense to me. Step inside, would you?

I have a Canon EOS Rebel XTi that I bought a couple of years ago as a gift to myself before I went on a trip abroad. I love it. It's a great camera, and I feel guilty because I'm sure I use a very small percentage of the camera's great features.. but.. um, be that as it may, I'd like to use it a bit more and I think this involves buying a new lens.

I only have a single lens right now. My goal, when I purchased it, was to get a decent "jack of all trades" lens... something engineering for no particular use that would take good "point and shoot" photos. To that end, I bought a Canon EF 28 - 105mm 1:3.5 - 4.5 lens. I've been very happy with it.

However, recently I've been getting into model making, and part of what I want to do is exhaustively photograph said models. My camera and my "stock" lens do great for some of this stuff, but what I really want is the ability to take some really nice macro shots of some of the really fine detail.

So, I've done some research, and the "INTERNET" seems to think that this is a great macro lens for the Canon XTi. For those opposed to link clicking, it's a EF 100mm f/2.8 Macro lens.

Now, I would just blindly click "BUY" but I don't want to be that guy. I want to try to understand what I'm getting at here, because some things don't add up.

My basic, brutish knowledge seems to break down like this - it seems like lenses have two basic features.. maximum aperture and focal length. Ok, so, the textbook definition of focal length (which you already know) is "focal length is measured in millimeters (mm) and it represents the distance from the optical center of a lens to the digital camera sensor when the subject of the photo is in focus." So, if I want to be taking close up macro shots of my models, it would seem that I would want a low focal length. That's one of the main problems with the lens I have now - whenever I get close enough to pick up the detail I want to capture in one of my shots, I can't focus it. Yet, from everything I've read, 28mm is a pretty low focal length, right on the edge of a wide-angle lens, so I'm wondering why that gives me so much trouble. This is even more confusing because the macro lens I link above is a fixed 100mm focal length, which seems *worse* than the lens I have now.

The other issue is also aperture... aperture is how wide the lens can open up to let light in. So, the lens I have now is a f/3.5 - 4.5. I would assume that for macro shots maybe I would want a little bit of a lower aperture? I notice the macro lens I link up there is a f/2.8, for example.

But, of course, what I find most confusing is that none of this seems to define what a macro lens is - it seems that a macro lens is a "a lens that can achieve a magnification of 1:1. That is, an object is the same size on the sense as it actually is. That is, an 18mm long bug will take up 18mm of the sensor or film frame. It generally does this by being able to focus quite closely." Ok, great, but where is this defined by the technical specifications of the lens? Do you just look for a lens that had the word "macro" in it or can its magnification be derived from the other technical stats?

And now I have a headache.

So, to summarize... I have a Canon XTi. I want to be able to take beautiful macro photographs of fine detail on my model, and I want to purchase a macro lens that will help me achieve this. Except I'm stupid and I don't understand.
posted by kbanas to Media & Arts (23 answers total) 5 users marked this as a favorite
My suggestion is a 50 mm macro. The wife has the Canon 2.5 50 mm compact macro. Super lens and runs about $250. I don't think you need a 100 mm macro.

And yes, macro lenses will say "macro" in the description.
posted by DieHipsterDie at 12:37 PM on June 29, 2010

I'm not qualified to make a recommendation on a specific lens, but you should definitely check if there are any photo shops nearby that will rent the lens you're considering to you. I rented a 10-22 Canon lens (normally a $600+ lens) for $20 for a day. I shot a ton of photos of my office and got a good feel for the lens. This is a small price to pay, in my mind, to make sure you'll like what you buy.

Check and see if any local pro photography shops/labs rent lenses. You'll feel better if you get to try before you buy.
posted by disillusioned at 12:40 PM on June 29, 2010 [2 favorites]

Fixed focal length lenses - "primes" - are good. Fear not the primes. Primes are your friend. Primes tend to be sharper and faster than equivalent zooms.

A practical advantage of a macro lens is the fact that they can focus so close to an object. In certain situations, a 100mm lens may be superior to a 50mm lens in this respect as well, as while you want to focus close up, you don't want to be so close up that you're casting a shadow on what it is you're trying to shoot. Then again, given your camera's crop factor, this difference might not be so important at all.

"Crop factor" refers to how the field of view on your camera is going to be narrower than if you were shooting on 35mm (or full frame, like on a 5D). Multiply the lens' focal length by 1.6, as the XTi is a 1.6x crop sensor. On your XTi, the FOV will be as if you're shooting with a 160mm lens. However, since you're buying this lens with an eye to doing macro photography, this won't really be that important; you'll just have to "zoom with your feet" if you're not getting what you want in your frame. OTOH, you may wish to go for the 50mm macro lens, as it will have a FOV equivalent to that of an 80mm lens with your camera's crop factor. This depends on how big your models are, how detailed your details will be, and how large of a space you have to light and shoot your models. If you are shooting tiny, specific details, you should get the longer lens; if you are shooting larger objects, then you should get the wider lens.

Now, earlier I used the term "faster" to describe a lens. For a lens to be "faster" means that it can let in more light by opening its aperture further. A 2.8 lens is faster than a 3.5 lens. Generally, faster is better, but since you're taking shots of your models, I don't think this will be very important. Your models are your own and are sessile; they won't hop about like bugs at dusk might. As such, you should take this opportunity to light your models well enough such that you won't need to open your lens all the way up to 2.8. Lenses tend to be less sharp when they're opened all the way up, and you're also more prone to glare this way.

I don't own the 100mm macro lens you describe, but the reviews I'm looking at seem basically ecstatic.
posted by Sticherbeast at 12:47 PM on June 29, 2010 [1 favorite]

There's a third component of "measuring" a lens which is relevant here - minimum focus distance. A lens is "macro" when its minimum focus distance is short enough that you can take pictures of objects that are about the size of the sensor itself. Deriving the maximum magnification distance from the focal length and the minimum focus distance isn't an easy thing to do, but this is a listed specification on all lenses claiming to be "macro" (for example, the EF 50mm Compact Macro has a maximum magnification of 2:1 (at maximum, 70mm object fills a 35mm frame))

In terms of focal length, you probably actually want a longer focal length for smaller objects. As the focal length gets shorter, you'll have increased perspective distortion due to the object being closer to the lens. It sounds like you're confusing focal length with focus distance -- the focal length basically describes the angle of view provided by the lens; the focus distance describes how far away from the camera the focal plane is.

Aperture, for your application, is probably not terribly important. The depth of field when taking pictures of small objects is quite shallow, so in most cases you'll be stopping down to f/11 or further just so your entire model can be in focus. The advantage of the f/2.8 aperture on the 100mm Macro is that it's a fantastic lens for non-macro shooting as well.

The EF 100mm f/2.8 Macro is a superb lens for the application you're describing. I own this lens and would recommend it to anyone.
posted by 0xFCAF at 12:50 PM on June 29, 2010

I think you're confusing focal length with minimum focus distance. Minimum focus distance is, of course, how close you can get to the subject and still focus on it. This is where you're running into a problem with your current lens, because when you get close enough to get the framing you want, you can't focus there.

The 100mm macro lens you're looking at has a minimum focus distance of about 1 foot, which you can find out by looking at the detailed specs on various web sites. And that is, I think, measured from where the sensor in the camera is, not the front of the lens. I have this lens and would say you can get pretty damn close to things and still focus on them.

The 100mm focal length describes, basically, the "amount of zoom". With your current lens, when it's at its widest zoom, the focal length is 28mm, and zoomed in as tight as it will go, the focal length is 105mm. So a 100mm macro will give you about the same framing as your current lens does when zoomed all the way in. You'll just be able to focus a lot closer because of the shorter minimum focus distance.

You are likely going to want a lot smaller aperture than f/2.8 (higher numerically) because when you focus this close, the depth of field is very shallow. In other words, only things in a very narrow range of distances will be in focus, and everything else will be blurred. You have to bring the aperture way down to get acceptable depth of field for a lot of macro photography. Like F/11 or F/16 is not at all unusual.

A lot of lenses say "macro" on them when they have some kind of ability to focus at a short distance. These are often not true macro lenses. The definition you read is the right one -- it's a real macro lens when it can produce an image on the sensor that's at least as big as the subject. That's described in the specs as a 1:1 magnification. That's as big as many macro lenses go, but there's at least one out there that goes up to 5:1 (fills the picture with a grain of rice!)

In a nutshell, a 100mm macro will let you take a picture of something about the size of a coin and fill the whole picture with it. It'll be able to focus close enough to actually do that. It will be difficult to get much of the picture in focus unless you use a very small aperture, but you can do that with the lens you're considering. Holding the camera very steady and lighting the scene are additional challenges when photographing very small things.
posted by FishBike at 12:51 PM on June 29, 2010

The lens takes you halfway. The rest is a combination of lighting, composition, and camera settings. This link might help.
posted by jnrussell at 12:52 PM on June 29, 2010

Also, when you're shopping for lenses, try searching for the exact product name (in this case "Canon EF 100mm f/2.8 Macro USM") on Flickr. Metadata dorks like me will tag their pictures with the lens/cameras they used and you can see tons (> 28,000) of examples and check the related tags for applications closer to yours.
posted by 0xFCAF at 12:56 PM on June 29, 2010

Your conception of focal length seems to be muddled with minimum focus distance. Without getting too technical, the 100mm lens will have the same angular field of view as your zoom lens at 100mm. Wha makes the macro lens ideal for close ups of small subjects is that the lens design allows it to focus at much, much shorter distances compared to a
traditional design, so that same angular field of view can be filled by a very small subject. This comes at a price. The lenses are more expensive and aren't as fast (let in less light at max aperature), but in this case faster than your consumer zoom.

The Internet is a great wealth of technical information if you want more of
that, but from a practical perspective, here is how I think you should decide: look through your 28-105 at the long end of the zoom (105mm) and fill the frame with a quarter. The 100mm you are
considering will focus on that quarter filling the frame. Is that the lens you want? In my opinion, I think you have made a
suprisingly good choice for a novice photographer. The lens you are considering is widely conisdered to have unrivaled image quality among 35mm SLRs. It is sharper than professional lenses a full order of magnitude more expensive, which will matter alot since you body has a cropped sensor. If you move up to a full frame one day, this lens will still retain its relevancy. It has other good uses too. Action shots, e.g. sports photography, especially on a cropped sensor. Portraits may look a little flat on a
cropped sensor with it, but this lens is also a favorite of portait photographers when mounted on a full frame body, because it is sharp wide open, and the background blur is rendered really nicely.

Go for it. You're making the right choice.
posted by [expletive deleted] at 1:01 PM on June 29, 2010

As one new macro lens user to another: macro lenses really love ring flashes.
posted by bonehead at 1:01 PM on June 29, 2010

Also, when you're shopping for lenses, try searching for the exact product name (in this case "Canon EF 100mm f/2.8 Macro USM") on Flickr. Metadata dorks like me will tag their pictures with the lens/cameras they used and you can see tons (> 28,000) of examples and check the related tags for applications closer to yours.

This is an excellent idea, and taking a few seconds to do this right now uncovers many photographers making lovely images with your same exact lens/camera combo.

As one new macro lens user to another: macro lenses really love ring flashes.

Make your own ring flash.
posted by Sticherbeast at 1:11 PM on June 29, 2010

That lens is fantastic. Go to Fred Miranda or POTN and do a few searches. Everyone loves that lens for macros and other things for that matter.
posted by Silvertree at 1:18 PM on June 29, 2010

I own the lens in question, and believe it would be perfect for your uses. You're going to want a lot of lighting for macro, even more so than you would a normal shot.

Here's a sample shot of a light filament from a lightbulb I took a long time ago, should give you an idea of the scale you're looking at with this lens. Like the others have said, the closer focusing distance in combination with the longer focal length ends up being a net benefit for you.
posted by jangie at 1:18 PM on June 29, 2010

Ok. I am convinced.

I will buy said lens. Thank you guys.

Now, two other issues..

1. A ring flash, eh? Any suggestions?

2. I also get the sense that for this kind of photography a tripod and remote trigger of some kind are almost a necessity - there's not going to be any "holding the camera very carefully and pushing the trigger". Any suggestions? Things to look out for?
posted by kbanas at 1:22 PM on June 29, 2010

Like, why do they sell tripod kits for the camera, and then additional "Tripod Mount Ring" for the lens? I guess I don't understand how to the two relate.

Anyway, you guys are awesome as always.
posted by kbanas at 1:28 PM on June 29, 2010

I usually just use the timer function on the camera. Using a flash is an alternative to needing a tripod in many ways.
posted by bonehead at 1:30 PM on June 29, 2010

First, the 100f/2.8 is really awesome for macro. If you get it, and don't like it, get your head examined. If you want to focus *closer*, you can get an extension tube and focus just about inside the lens.

Second, the tripod ring mount is so the tripod is mounted to the lens, not the camera. Better balance that way; also, you can loosen the ring and change from portrait to landscape really easy.
posted by notsnot at 1:41 PM on June 29, 2010

Yeah, the timer function works great in lieu of a remote switch. I can't speak to the Rebel specifically, but my 30D has a function in the settings where I can change the timer from 10 seconds to 2 seconds. It makes this kind of shooting much easier. All you need to do is get your hand off the body for long enough to keep the shake to a minimum.
posted by quin at 1:49 PM on June 29, 2010

Imagine you've got the camera mounted landscape on a tripod, the image is framed just how you want, lighting just so, and now you want to get a couple shots portait. You rotate the camera on the tripod, and now the lens is four inches away from where it was; your framing changes, lighting changes, etc.

The "Tripod mount ring" lets you connect the tripod not to the bottom of the camera, where changing orientation changes the entire setup of the shot, but basically to the lens, so you could just rotate the camera to portrait without changing where it's pointing or your lighting setup, etc. You're basically rotating the camera about the centerline of the lens.

Remote trigger is nice, but not essential. Self timer works fine. If you're using a flash even that isn't required. What you want to do is avoid the potential motion of the camera when you press the button. Flash freezes motion anyway so it's not a concern in that case, generally.
posted by chazlarson at 2:41 PM on June 29, 2010

Self-timer works well and many cameras are controllable via a cable connected computer which can make the process go that much faster.
posted by mmascolino at 3:39 PM on June 29, 2010

A ring flash, eh? Any suggestions?

I've been pretty happy with the Canon one, the MR-14ex. It attaches directly to the end of any of the Canon macro lenses, which is nice. It's a bit pricey though.

You can light scenes in many other ways for macro photography, just remember that at small sizes and up close, the camera itself casts an enormous shadow. So forget about any on-camera flash or any light from behind you.

A ring flash surrounds the lens, so you get no shadows at all. It's designed for use at close range, where a regular flash may have trouble lowering the power enough to avoid over-exposure. And the Canon one, at least, gives you independent control over the two halves of the ring, so you can get some shadows with it if you want.

there's not going to be any "holding the camera very carefully and pushing the trigger"

Sometimes you can get away with hand-holding the camera, especially with digital where you can take a ton of shots and keep the best ones. The issue with macro photography isn't just motion blur from a long exposure, which a flash will indeed help with.

The problem is mainly that depth of field is so thin that your carefully-focused shot will be thrown out of focus by moving the camera a few millimeters, and a flash won't help with that. Only a tripod will hold it steady enough to keep things in focus reliably. In fact the easiest way to focus at high magnification is to focus the lens for the magnification you want and then move the camera back and forth to focus. You can get macro focusing rails that allow you to do this easily with the camera on a tripod.

For getting started, you'll be OK with a regular tripod as long as it lets you get close enough to your subject. You'll probably be OK without a ring flash as well if you get creative with your lighting, but that's harder, so if you really get into it, a ring flash should be your next purchase after the lens itself.
posted by FishBike at 4:09 PM on June 29, 2010

I own the EF 100 2.8 and I freaking love it. I love it so much that I am seriously considering ponying up the full price for the tripod mount ring. You will also love it, and if you don't, the resale on Craigslist and ebay is currently only about $75-100 below the best prices for new ones online.
posted by MrZero at 5:47 PM on June 29, 2010

You could get away with a desktop tripod like the Gorillapod or a beanbag if you're taking pictures of models.

Do you have a lightbox? If you aren't ready to invest in a ring flash quite yet, you can get good results out of that kind of setup. You could even build one with a boxcutter, a roll of rice paper, and a 16 inch cardboard cube.
posted by Sallyfur at 12:53 AM on June 30, 2010

I have used the 100mm 2.8 macro lens extensively, both in the field and the studio, and it's an extremely fine piece of glass.

Regarding the ring flash - it's great for filling in shadows in your model, but it will give you a very particular kind of light. You could also use regular speedlites, like the 430EX to give you a bit more shape in your light.

Also, check out this DIY lightbox from Strobist.

If you want to get a bit more flexibility with your light, the Canon MT-24EX twin light system is extremely good, but a bit more expensive.
posted by Magnakai at 2:42 AM on June 30, 2010

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