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10-15-2008, 07:27 AM   #1
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Macro - beyond 1:1

Noobie question time.

It seems like:
3:1 is normal close focus
2:1 is "macro" close focus on a Sigma/Tamron zoom etc
1:1 is true macro

But can you go further than that, e.g 0.5:1 or 1:2 (or indeed, anything below 1:1)?

10-15-2008, 07:33 AM   #2
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QuoteOriginally posted by Richard Quote
Noobie question time.

It seems like:
3:1 is normal close focus
2:1 is "macro" close focus on a Sigma/Tamron zoom etc
1:1 is true macro

But can you go further than that, e.g 0.5:1 or 1:2 (or indeed, anything below 1:1)?
You have it backwards. Think of the ratio as a fraction:
1:2 = 1/2 = half life size
1:1 = 1/1 = life size
2:1 = 2/1 = twice life size

Anything below 1;1 should be considered close focus, and is by Pentax, but not by Tamron or Sigma, who insist on calling close focus lenses "macro".

It is defiinitely possible to go to 2:1, 3:1, even 5:1 using diopters, bellows or reversed lenses.

Last edited by audiobomber; 10-15-2008 at 08:26 AM.
10-15-2008, 07:35 AM   #3
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You have those figures the wrong way. 1:1 means that something that is 1cm wide for example, is 1cm wide on the sensor too. 3:1 would mean that an object 1cm wide would be 3cm on the sensor. With 1:3 the object would be 3,3mm on the sensor.

You can get bigger than 1:1 quite easily. Just stack those extension tubes and turn the lens around, and there's even some lenses that produce bigger than 1:1 without any help.
10-15-2008, 07:38 AM   #4
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This is about 3:1 using the Raynox M-250 add on lens.





10-15-2008, 07:50 AM   #5
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Oh, if only I had a Canon body ..... HERE.
This lens almost makes me want to buy a cheap 400D.

This is a 50% crop using a Tamron 90mm macro with a Vivitar macro teleconverter.
I couldn't work out the magnification though :0)

10-15-2008, 07:56 AM   #6
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I slapped together an unsusual macro setup a while ago, made using a 135mm M42 lens with a reversed 24mm on the end. Crazy magnification, I worked out that it was something around 5.9:1! It would have been even more if I used some extension rings too.
I don't have any pics of the actual setup, but it was mounted of my K10D with an old flash bracket as a balancing support for the lenses + camera combo - which was attached to a heavy S-shaped bracket, which was in turn clamped to a sturdy table. I got some crazy photos with it, but I often had a lot of trouble with bad image contrast and mirror slap. Also, the exposures could go up to 30 seconds without a flash. But probably the worst problem was that the DoF was so shallow that simply placing objects and finding them in the viewfinder was no easy task.
Here's some of the better images I got:

The asterisk from an IBM "golfball" printer head:


A tiny lead fishing weight and wire:


Part of a carpel from an amaryllis flower:


The edge of a steel nut:


I must try this super-macro setup again sometime, I'll definitely get some better shots then. I'll probably use some flash this time too.
I just have to wait a few weeks for my camera to come back from being serviced...!!!
10-15-2008, 07:59 AM   #7
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how do you calculate the magnification when using several diopters?
10-15-2008, 08:17 AM   #8
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@Alfisti: Great photos!
@Mike.P: Wow!
Thanks to all for the info - I had my ratios backwards.

I find myself taking a lot of close-up photos with my Tamron 18-250 on my K10D, and was thinking of buying a true macro lens in the range around 100mm +- 20/30, so I can hopefully do better. I believe from other threads that all of those from Pentax and major 3rd-party brands are pretty good. I was going to ask whether one of them gave a higher magnification than any other, but I guess from the photos posted above, the answer is that any of them can get closer up with the aid of a teleconvertor or an add-on lens.

Thanks again,

Richard

10-15-2008, 09:10 AM   #9
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A little math

Here's a practical example of how to determine macro magnification, cooked up by me. I consulted no guides for this, I just felt like getting the way I do it out of my head.

For instance:
A typical APS-C imaging sensor is 23.6*15.7mm.
A typical 10.2Mp sensor gives an output of around 3896*2616 pixels, so you can say that's (3896 / 23.6) = 165 pixels per mm of sensor.
Thus a 1:1 macro lens would theoretically reproduce 1mm as 165px wide on a 10.2Mp sensor. We'll call this the pixel factor.
(Naturally you can calculate your own depending on the size of sensor and megapixel count.)

a = the physical object's width in mm. The measurement should ideally be on a level horizontal plane relative to the camera.

b = the object's width in pixels from the captured image.

p = pixel factor.

M = the magnification factor.

M = b / pa


I think this is correct... Let's test.

You measure a bead with a micrometer - it measures 4.3mm . You put it in front of your macro setup and take a picture. (a = 4.3)
You load the image into Photoshop. You find out using the measure tool that the bead is 2433 pixels wide. (b = 2433)
You're using a K10D, so your pixel factor is 165. (p = 165)

2433 / (165*4.3) = 3.4
So in this case, the magnification ratio is 3.4:1.


If anyone wants to criticise this, feel free. I'm not completely sure of it myself!
10-15-2008, 10:36 AM   #10
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You can take those above withthe 18-250, well pretty close anyway. You need a proper flash (essential as you'll be at f/22) and a close up lens like the Raynox.

QuoteOriginally posted by Richard Quote
I find myself taking a lot of close-up photos with my Tamron 18-250 on my K10D, and was thinking of buying a true macro lens in the range around 100mm +- 20/30, so I can hopefully do better. I believe from other threads that all of those from Pentax and major 3rd-party brands are pretty good. I was going to ask whether one of them gave a higher magnification than any other, but I guess from the photos posted above, the answer is that any of them can get closer up with the aid of a teleconvertor or an add-on lens.

Thanks again,

Richard
10-15-2008, 11:01 AM   #11
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QuoteOriginally posted by Mike.P Quote
Oh, if only I had a Canon body ..... HERE.
This lens almost makes me want to buy a cheap 400D.
You'd find very limited use for it. It's a highly specialized lens and quite difficult to work with.
10-15-2008, 11:47 AM   #12
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QuoteOriginally posted by Spongefingers Quote
Here's a practical example of how to determine macro magnification, cooked up by me. I consulted no guides for this, I just felt like getting the way I do it out of my head.

For instance:
A typical APS-C imaging sensor is 23.6*15.7mm.
A typical 10.2Mp sensor gives an output of around 3896*2616 pixels, so you can say that's (3896 / 23.6) = 165 pixels per mm of sensor.
Thus a 1:1 macro lens would theoretically reproduce 1mm as 165px wide on a 10.2Mp sensor. We'll call this the pixel factor.
(Naturally you can calculate your own depending on the size of sensor and megapixel count.)

a = the physical object's width in mm. The measurement should ideally be on a level horizontal plane relative to the camera.

b = the object's width in pixels from the captured image.

p = pixel factor.

M = the magnification factor.

M = b / pa


I think this is correct... Let's test.

You measure a bead with a micrometer - it measures 4.3mm . You put it in front of your macro setup and take a picture. (a = 4.3)
You load the image into Photoshop. You find out using the measure tool that the bead is 2433 pixels wide. (b = 2433)
You're using a K10D, so your pixel factor is 165. (p = 165)

2433 / (165*4.3) = 3.4
So in this case, the magnification ratio is 3.4:1.


If anyone wants to criticise this, feel free. I'm not completely sure of it myself!
This is cool. Not sure if it's correct, but it sounds like it is.

c[_]
10-15-2008, 12:17 PM   #13
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QuoteOriginally posted by ftpaddict Quote
You'd find very limited use for it. It's a highly specialized lens and quite difficult to work with.
Indeed, which would suit me quite nicely.
At least we are finally going to get a decent macro ringflash at long last.
Bit like a bus, you wait ages and then 2 come along at once (Sigma & Pentax).
10-15-2008, 12:45 PM   #14
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Would definetly find a use for it. Use an Olympus 20mm macro sometimes. Its way past 1:1 mag. Tricky to use without focus rail. Will mount it on Pentax K bellows and use it on digital one day. Might be easier to use on Oly E330. have to hook that up.
thanks
barondla

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10-15-2008, 12:50 PM   #15
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For inexpensive 2:1 macro, simply reverse a 28mm lens on the camera body. My 28/3.5 M series would give about 2.1:1 when I mounted it on a 52mm reversing adaptor with a 49>52 mm filter step up ring.

For acceptable results with reversed lenses, you must use a prime lens. Zoom lenses do really strange things when reversed. Wide angles give more magnification than telephotos when reversed. The wider the lens, the bigger the magnification ratio.

One can also add an extension tube and/or bellows between the camera and lens for more magnification. Take note that it really gets dark in there, and the depth of field is microscopic. A geared focusing rail is pretty well a must.
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