macro ratio

[matilda]

I'm thinking of getting a macro lens.

I've noticed that the minimum focal distance is around 20cm (at the lens i'm looking at).

I've also noticed that some come with a 1:1 ratio, and others 1:3.

My question is, 'is there much of a difference from the 1:1 ratio as there is to the 1:3?'

At the moment i'm looking at these ones

Tamron SP AF90mm F/2.8 Di Macro Lens
Sigma 18-50mm F2.8 EX DC MACRO /HSM Nikon Mount
Nikon AF 60mm Micro 60 f/2.8D Lens

But i'm just a bit confused.

So if someone could shed some light, that would be greatly appreciated.


TIA

[ving]

1:1 ratio is basically where the object being photographed is is life sized whe the picture is reduced to the same size of the chip. 1:3 is one third the magnification of 1:1.

so in shorter terms 1:1 gives more magnification than 1:3

hope thats a start for you :)

[Steadyhands]

My guess will be the Sigma lens you mention is the one with the 1:3 ratio? Normally a macro lens is a prime lens (fixed focal length) like the 90mm and 60mm lenses you've listed. A "true" macro lens is one that has a 1:1 ratio. What does this ratio mean I hear you say?

It means a shot taken of a flower 10mm across will be reproduced on the sensor as 10mm across. This means it reproduces it life size. Think of it like the lens is a projector and it is projecting the flower onto a screen - the sensor is the screen in this case. I won't go into what size it is after the image is saved and displayed on the computer screen or printed - this gets very confusing and is effected by many things, but you do have a photo of a flower at a ratio of 1:1.

The 1:3 lens doesn't reproduce the subject to the same size it is in real life, but smaller. Seeing you are often trying to take a macro shot of something small this might not be the best.

To confuse the issue a little, the true macro lenses will have a series of markings on them something like 1:1, 1:1.5, 1:2, 1:2.5, 1:3 etc. If you use the lens in AF mode and let the camera Auto Focus on you subject you will end up with one of these reproduction ratios, and probably a subject that is just slightly less than life size. At 1:1.5 the subject is about 2/3rds the size it would be in real life. ie 1/1.5=0.6666. So now your 10mm flower is covering only 6.666mm of the sensor.

Next switch off Auto Focus, turn the lens focus mechanism to set it to 1:1, look through the viewfinder to see an out of focus scene. Next move your body back and forward until the scene is in focus and take the shot. You have now taken a true 1:1 macro shot.

Most times the majority of macro photographers will not necessarily go to this trouble. I know that some times I will use Manual Focus and keep my body stationary and other times I will set the 1:1 ratio. I personally don't care that much if the shot was 1:1 or 1:1.5. I'm more likely to care if the ratio is larger than life size. ie 2:1 I can get a reproduction ratio like 2:1 by adding Extension tubes between the camera and the macro lens - but this is another story also.

I hope this made sense?

[matilda]

thank you for the replies.

and yes it makes sense to me, you just explained it further than what I knew :p

I would prefer a fixed focal length.

if you recommend something feel free to post it.

[Steadyhands]

No experience with lenses for Nikon but David probably know a fair bit. Usual story is that most macro lenses are very good and it's hard to go wrong. I normally tell people to start off with a lens around the 100mm area - 90, 100, 105, not a lot of difference. This focal length is a good balance between working distance (how far you are away from the subject) and field of view.

[J.davis]

The Tamron 90 has got good reports - thats why I bought mine.:th3:
If I had my choice again I think I would have gone with the Sigma 150 - bit of extra working space.

[I @ M]

Macro is fun but it can be a little bit harder to get exactly the shot you want than more regular styles of photography.
A good tripod is a must have item.
The Sigma 150mm is well regarded and lets you stand back further from the object that you are photographing ( good for letting more natural light on the subject ) but is larger and more expensive.
The Tamron 90mm is capable of some beaut photographs and works well as a portrait lens, the newer versions have a built in focus motor. ( AFS )
There are 2 versions on the Nikkor 60mm on the market, the AF version and the AFS version. By all accounts the AFS ( newer ) has improved an already well regarded lens.

Your decision comes down to the factors of weight, price and how far away from your subject that you want to be.



I've noticed that the minimum focal distance is around 20cm (at the lens i'm looking at).


The question came up a while ago, and minimum focus distance is usually measured from the subject to sensor ( or film ) and not from the subject to the front end of the lens body / hood.
There is a quick diagram I drew in this thread to explain it visually.
http://www.ausphotography.net.au/forum/showthread.php?t=36657

[matilda]

lol... love the drawing, and yes that makes sense.

Last night while lying in bed i though about it more, and i think i would prefer something at least around 90 ml.

If I have to spend a lil more, so bit it, more time to save then.

and I have a manfrotto 190 tripod, which i took out of storage only last week.

[ricktas]

I have both the tamron 90mm and the Sigma 150mm. I use the Sigma most of the time now, I just think it is a slight bit sharper than my Tamron. But as their are variances between every lens, it could just be my copies. As J.davis said, the 150mm gives you a bit more room. So say you are photographing a spider, the 150 lets you be that bit further away. Getting in close to some subjects can make them skittish.

[Miaow]

I've got the Tamron 90 macro - It seems a good lens :)

[ving]

No experience with lenses for Nikon but David probably know a fair bit. Usual story is that most macro lenses are very good and it's hard to go wrong. I normally tell people to start off with a lens around the 100mm area - 90, 100, 105, not a lot of difference. This focal length is a good balance between working distance (how far you are away from the subject) and field of view.i dont really have much experience with nikon stuff either... but as a general rule most macro lenses are sharp and good. nikon macros are branded micro rather than macro i believe.

the longer the focal length of the lens the more working room you will have.
and finally the tamron 90mm does 1:1 and will serve you well... oh and its relatively cheap. that said i use a really old nikon lens (55mm f3.5) that only manual focuses and i have to self meter, lol. but it works good (just look thru the macro forum at some of my results.:efelant: