Macro 1:1. What does it mean?

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RichieRich

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This is something which has been bugging me for a while, and now that i'm thinking of buying a macro lens I really need to know the answer...

I often read that a true macro lens is one that produce images on a 1:1 ratio image, meaning that the image on the sensor is the same size as the object being photographed.

However, this is what confuses me. Frequently I see photos of insects such as flys etc where the entire head of the insect seems to fill the frame. If this is so, and a 1:1 macro lens is being used, doesn't it imply that the fly had a head the size of the camera's sensor!!!

I'm assuming that most of these closeups I've seen haven't been drastically cropped.

Clearly I'm missing something here...can anybody fill me in?

Thanks.
 
You are correct, almost.
Correct is your statement that the that the image on the sensor is the same size as the object being photographed.
The bit you are missing is the length of the lens.
The human eye is 55mm (ish) in 35mm terms. So a 105mm lens gets you twice as near and a 180mm ~3X. Plonk this on a 1.6x crop and you dont use the whole 35mm area so an even greater effective zoom (the focal length of the lens does not change).

Then once you've taken the shot you crop the begeeezers out of it :D

(thats a bit of a lie too since the nearer you focus the less effective the zoom becomes, but thats too techie for me)
 
RichieRich said:
I often read that a true macro lens is one that produce images on a 1:1 ratio image, meaning that the image on the sensor is the same size as the object being photographed.
Click to expand...

Macro is 1:1 or greater. A Canon MP-E65 will go to 5x life size.

Bob
 
here's an example for you. the canon 30D's sensor size is 22.5x15mm, on this sensor with my reversed 35-80mm i can fill the frame with 12mm on a ruler - like this...

scalesm.jpg


This equates to me getting about 2:1 magnification on my 35-80 lens, if it were a canon 100mm macro, closest focus i would get 22.5mm of a ruler in focus on the longest length.
 
oldgit said:
The bit you are missing is the length of the lens.
The human eye is 55mm (ish) in 35mm terms. So a 105mm lens gets you twice as near and a 180mm ~3X. Plonk this on a 1.6x crop and you dont use the whole 35mm area so an even greater effective zoom (the focal length of the lens does not change).
Click to expand...

Paul, I have no idea what you're trying to say there, the more I read it the less it makes sense to me :bonk:

Anyway, a 1:1 macro lens reproduces lifesize on the sensor regardless of focal length or sensor size. The only difference focal length makes is the distance you need to be from the subject, longer lenses have a longer working distance. Not even the DoF changes as DoF is only affected by magnification and aperture - 1:1 is the same magnification regardless of focal length.

But to answer the original question, yes a LOT of cropping goes on for macro shots, 100% crops are not uncommon for showing the details in a fly's eye.

Sometimes extension tubes are used in combination with a macro lens to increase the magnification to around 2:1. Reversed lenses are another option as well. The MPE 65mm is also becoming more popular but is a specialist item, it's offers between 1x and 5x lifesize but can't be for anything but macro.
 
I thought I understood completely when I read Paul's post, however, then I read Bobs which implied that the magnification would be lower on a 105mm macro than with an 80mm lens (as with the macro 22.5mm of the ruler would be in focus at the closest focus).

Andy, you say that it only effects working distance? So, comparing say, the Tamron 90mm with the 180mm, the 180mm gives you the benefit of being able to be further away from the subject. I don't fully understand this because both have similar minimum focus distances, consequently, surely the 180mm will provide an image which is bigger on the sensor at that distance.

Thanks for the replies chaps.
 
The focal length for any lens is only true when it's focused at infinity. As focusing distance decreases the focal length gets shorter. With a macro lens this shortening can be more noticable than a "normal" lens and the longer the quoted focal length the more it will shorten at close focus. Even so the Tamron 180mm min. focus is still nearly double that of the 90mm - (0.47m compared to 0.29m).

Bob didn't use a 1:1 macro lens for his example - he reversed a "normal" lens which does give a high magnification but the working distance becomes a matter of a few cm.
 
Thanks very much. It's starting to make sense now. Sorry, I thought that the minimum focus distance of the 90mm and 180mm was different.

So, the advantage of having a macro with a longer focal length is purely that it gives you more working distance with the subject, which I imagine may be more important when it comes to insect photography etc. Also, I imagine that such a lens could double up as a prime for portraits etc.

I have to wonder why manufacturers don't just produce macro lenses which are capable of magnification ratios of 2:1 etc straight out of the box. It must be possible with extension tubes, but then you're going to be stopping the lens down.

Good information. Thanks again.
 
RichieRich said:
.....I have to wonder why manufacturers don't just produce macro lenses which are capable of magnification ratios of 2:1 etc straight out of the box. It must be possible with extension tubes, but then you're going to be stopping the lens down.
Click to expand...

To keep the same aperture at 2:1 would increase the cost of the lens quite a bit. The MP-E65 is about 2.5x the cost of the EF100/2.8
Macro lenses by design have a fair amount of internal extension. To increase the magnification for any given focal length then you'd have to design in more internal extension. Adding tubes effectively adds internal extension on the outside....if that doesn't sound stupid.

Bob
 
RichieRich said:
So, the advantage of having a macro with a longer focal length is purely that it gives you more working distance with the subject, which I imagine may be more important when it comes to insect photography etc. Also, I imagine that such a lens could double up as a prime for portraits etc.
Click to expand...

The only drawback with the extra distance is camera shake
 
theory said:
The only drawback with the extra distance is camera shake
Click to expand...

It's certainly a drawback but not the only one. Reduced DOF can be a huge problem for longer focal lengths. Another issue is that much more extension is required to gain additional magnification.

Bob
 
Canon Bob said:
It's certainly a drawback but not the only one. Reduced DOF can be a huge problem for longer focal lengths. Another issue is that much more extension is required to gain additional magnification.

Bob
Click to expand...

ah really? that would explain quite a few things and now makes me want a nice short macro lens now too.

:thumbs:
 
theory said:
ah really? that would explain quite a few things and now makes me want a nice short macro lens now too.

:thumbs:
Click to expand...

As a rough guide you can expect the following magnification factors by adding tubes....12mm and 25 mm to Canon's main macro lenses

EF-S60 1.28x 1.61x
EF100 1.19x 1..39x
EF180 1.09x 1.21x

The MP-E65 doesn't really take to tubes as the already high magnification factors possible give a very small minimum focus distance and tubes would likely move the focus point inside the lens.
One advantage of the EF180 is that it still produces good IQ with a 1.4x (and even a 2x) T/C although you do lose a little working distance.

Bob
 
pxl8 said:
Bzzzt!

DoF at 1:1 is the same for a given aperture regardless of focal length.
Click to expand...

Yep, I agree with that. The point is that very few shots are taken at exactly 1:1 as it would give be very limiting. The shorter f/l lens would show greater DOF more quickly as the lens was moved away from MFD.

Bob
 
You'd get exactly the same DoF with any focal length if you compose the frame so the subject is the same size on the sensor. If you take a shot at 1:2 or even 1:100 the DoF will be the same because DoF is a function of magnification and aperture - focal length makes no difference to DoF calculations. Yes I know all the DoF calculations are based on focal length but what they actually do is calculate the mag. factor based on focal length and subject distance.
 
Wow, there's so much quality information there. Given the advice it seems that I won't actually gain as much as I'd previously thought from spending more money on a lens which has a larger focal length. I.e you've probably collectively just saved me about £150.00.

Thanks everybody.
 
Right, I've been searching around and I think I've narrowed my choices down to the Tamron 90mm, the Tokina 100mm or the Sigma 105mm.

Amazon are doing the Tamron for £265.00 with free postage, which sounds good. I've also already got a Tamron lens which I'm qutie happy with (despite the noisy auto focus). I terms of resolution the Tamron seems to get excellent reviews.

Does anyone have any recommendations?
 
If the prices are simiilar then go for the sigma as you get just that bit more focal length and you can be a bit further from your subject and not scare the butterflies away!!
 
Pretty much all the macro lenses available at that focal length will do an outstanding job. The Sigma 105 is perhaps weakest in that the AF is quite slow which doesn't matter for macro as that's MF all the way but if you plan on using the lens for other stuff it might be an important factor. The Tamron is well respected - I think there's a Canon mount version in the For Sale section.

Really it comes down to the best deal you can get at the time, they're all great lenses and you could blind test owners of each lens and I bet they wouldn't be able to tell which one produced a shot even looking at a 100% crop.
 
I'm guessing that they are based in HK. Actually, I might be going to Japan tomorrow (that must sound like a strange statement) so I guess I could pick one up from there...

The Tokina is actually quite tempting, for build quality as much as anything else.
 
I can tell you that you won't be disappointed with the tamron 90mm - I have it and have taken some great shots. Its very sharp and lots of owners have said they've upgraded to the nikon 105mm VR macro lens only to lose sharpness.

Dunno about the others, I know they're all good but based on my own purchase you'll definitely be happy with the tamron. Photozone.de seems to rate it the most favourably too.

I've got a couple of shots in my zenfolio thingy if you want to check them out?
 
Thanks, actually, I was just checking out reviews on photozone.de, that's what made me consider the Tokina too as it performs almost as well in terms of resolution, but the build quality seems to be better.

Having said that, I only read good things about the Tamron. Perhaps it's a safer bet in that regard.
 
Check out fredmiranda for user opinions and also pbase and flickr for actual shots... I remember wondering which lens to go for and it was buying the 90mm tamron that made me such a fan of their lenses. The build quality is pretty naff tbh, nothing wrong at all - infact very sturdy and smooth action etc but they don't look like expensive lenses and aren't as big and heavy as the others so probably less attractive to your mates and other togs out there based on looks. Functionally speaking though - brilliant. If it weren't for the 90mm lens I'd probably not have considered the 17-50mm tamron I have which is just amazing and I have a nikon 70-200mm VR lens too so I have got some good glass to compare with ;)
 
The first lens I bought was a 17-50mm Tamron XR 2.8 Di II. I'm very happy with it. The build quality is quite good actually.
 
Ah brilliant well you know what to expect then... the 90mm is a bit better too being a macro prime, just a bit more specialised. :)
 
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