How do I increase my X factore on a macro

[guidocoza]

Hi guys
Got myself the awesome 150mm sigma 2,8. this is the 3rd macro lens and so far I would say the best. (Minolta 100, Canon 100mm b4)
I did some pretty good stuff with a Fuji s100fs and the Raynox achromat but with the new lens the achromat does not fit anymore. After I started to play around with focus stacking I would like to get higher magnification than the 1.1
Does anyone has played around with that focal length plus tubes / or dedicated close-up lenses and what is the best option when it comes to pic. quality.
B.T.W i did put my canon 1.4 tele converter in between but it does not really makes much of a difference
Thanks for your input and soon will post a pic or two
Guido.coza

[chauncey]

I use a Canon 180 macro and use the tubes as well as a 1.4 TC when I want to get more than 1:1 as well as using focus stacking, with the caveat that I shoot tethered using the Canon Utility software. Using the software allows me to be more precise in my focusing, plus I can control all the camera's functions from the keyboard.

[guidocoza]

Using the software allows me to be more precise in my focusing, plus I can control all the camera's functions from the keyboard.

Hi Chauncey
Thanks for the reply.
did some night shots with the software and find it great but how does it help you focus?? I normally focus manually as with the stacking I always need a different focus point.
How many tubes, and what length do you use?
Guido

[Stagecoach]

Hi Guido,

I would ask what you call the 'X' factor ? To me the X factor depends upon the subject generally.

Perhaps if you post an example of an image that you consider has this or one that you wish had it, it may assist in getting the right response.

Any use of TCs is going to reduce your lighting of which you are going to have to compensate for or lose IQ by being forced to use higher ISOs.

There's also a great difference in what is achievable depending upon whether you are attempting hand held in the field, static or moving subjects and tripod and studio work.

Grahame

[Geoff F]

What you are able to do, Guido, depends on your subject.

I mostly shoot live insects in their natural state so the only way of getting a larger image, without scaring my models, is to add a 1.4x converter to my 180 mm macro lens.

Adding extension tubes will get you physically closer, hence a larger image.

Their advantage is that they don't contain any glass so there will not be any quality loss. Possibly a slight light loss though. But only suitable if you are physically capable of moving closer.

The disadvantage is that you will lose the ability to focus at infinity; but not an issue for macro work.

And it is possible to use a mixture of tube and converter. I added a 12 mm tube to act as a spacer when using a Canon converter on a Sigma macro lens.

I did some quality tests with and without the 1.4x converter and found very little quality loss except for a slight reduction in 'contrast'. Often a different result when their are used on zooms though, particularly the cheaper versions.

[guidocoza]

Hi Grahame
thanks for the reply. I'm well aware that as greater the magnification the smaller the dof. for most field work the 150mm is just perfect. But when I find that less than 2mm fruit fly or crab spider than I would like to play around with higher magnifications. than with tripod, and even controlled conditions.
With tubes I do not necessarily loose light nor did I with my Raynox.
The question remains what is the best option if I want to increase the magnification on a dedicated 150mm macro lens?

[chauncey]

When I use the Kenko extension tubes I'll usually just plug all three of the on the lens...focusing is helped simply due to the larger laptop screen. This, of course, is of no value in objects that are moving.

[guidocoza]

Hey Geoff
Thats what I needed to know. I agree the loss in contrast is there but hardly noticeable. the problem is the longer the focal length the less "effective" are the tubes! You said you used a 12mm, how much adds this to your 180?
Will give it a bash with tubes and post at Ipernity or here!

[Stagecoach]

What you are able to do, Guido, depends on your subject.

Excellent comment !

[Geoff F]

I originally got tubes when using a 70-300 lens for macro work. A 25 mm tube got me around 1 ft closer, but that was from 4 ft to 3 ft which is different to a proper macro lens. It is only a couple of inches at best for a 25 mm tube with my 180 macro lens.

Normal focus with that lens is around 12 ins.

The 12 mm tube made little difference except it allowed me to fit a Canon converter to a Sigma lens; which didn't mate up otherwise due to the shape of the converter.

[Inkanyezi]

I'll try to get back to the original question, how to increase magnification.

The Sigma 150 mm macro lens is nominally 150mm focal length, but at short distances, its focal length is decreased, as it is inner focusing. This means that at the shortest distance, at 1:1 reproduction scale, the focal length is somewhere close to half the nominal focal length of the lens.

It takes some understanding of optical elementa to fathom how magnification will increase.

A lens that is placed at twice the distance of its focal length from the sensor will render a 1:1 image at a distance of four times the focal length from the sensor. Thus at 38 cm distance the focal length of the lens might be estimated to approximately 9 cm. To enlarge the image to 2:1 you need to extend about 9 cm more.

It is rather easy to understand that a shorter focal length will increase reproduction scale at the same extension, so for shooting very small objects, as fruit flies or anything at the same size, a shorter lens might be required, unless you have very large extension tubes. There's certainly a limit to how much extension that is practical, and as it is also very tricky to actually find the object that you wish to photograph at large magnification, a long lens might be very impractical.

For photomicrography, microscope lenses are often used, as they have very short focal length and at a close working distance, they can present large magnification on the sensor. Often no focusing helix or bellows are used, but only a macro slider that will let you move the entire camera with extensions back and forth and sideways. Also with a more moderate lens, as for example a 50 mm enlarging lens or an inverted wide angle lens, this setup works well. Still a large focal length is impractical and will not provide as much magnification as a short focal length at the same extension. The macro slide may also be used at the other end of the setup, moving the subject instead of moving the camera.

So a reasonable answer to your question is that the Sigma 150 mm lens is impractical for larger magnification than it is designed for. You'll do better with another lens if you want very high magnification. If twice life size is sufficient, a 10 cm extension might be the way to go, still working at a convenient distance, but with larger magnification. Beware that AF will not work well in such a setup, and you would benefit of a macro slide arrangement.

Regarding "light loss", there is an optical law we cannot break. Any extension will decrease the light falling on the sensor. Using 10 cm extension on the 150 mm lens set to its close distance, will decrease the effective aperture by about two stops, using only the smaller portion of its image that falls upon the sensor, which is only ¼ of the area of the image when used without the extra extension.

[guidocoza]

Hi Inkanyezi
Thanks a mill for your reply. Even though I have to read it another 3or4 times to fully understand it you confirmed my suspicion/fear. Another lens is needed if I want anything more than 2;1. I might see if I can get my hands on a reasonably priced 50mm1.4 and than use the tubes.
Ones again thank you for your detailed responce and I surely let you see the fruits of your advice
Warm regards
Guido

[Inkanyezi]

Beware that the large aperture lens might not be optimal for macro work. Probably it will fare better inverted, pointing its back toward the subject, which is accomplished with a reverse ring that screws into the filter thread of the lens. For this type of work, you might want a manual lens with an aperture ring. So you might as well get an old legacy lens (they are cheap), as it will not need to have the same mount as the camera. You get the reverse ring for the filter thread of the prime lens and the bayonet mount of your camera.

For focusing, moving the camera back and forth (or the subject) is most effective, and the SLR viewfinder or focusing aids might not work well. If you have live view on your camera it is a better option for framing and focusing.