SomeGuyWithACamera wrote:
I have been looking at the Laowa 60mm x2 myself. Does that 100mm have a focus ring or is it just by moving closer and farther from your subject?
It has a focus ring. As with other macro lenses you can also think of this as a magnification ring. The barrel has magnification marks on it, from 1:4 through 1:2, 0.75;1, 1:1, 1.5:1 and 2:1.
You can turn the ring to get to around the magnification you want, either by looking at the markings if you have enough experience with a subject/scene size to know what magnification you want to use, or you can judge it visually. You can then fine tune the focus either by turning the ring a little or moving the camera a little. I sometimes use the ring and sometimes move the camera.
The ring is conveniently wide and mine moves very smoothly. It takes you from infinity focus to 2:1 with a turn of around 120 degrees, and it goes from 1:4 to 2:1 with a turn of around 90 degrees. (With my double teleconverter setup ......
....... it goes from infinity focus to 8:1 with the same 120 degree turn, and from 1:1 to 8:1 with 90 degrees turn.)
I like to vary the magnification a lot, not just between subjects but for a particular subject, so I can get a range of shots from whole body in to for example just the head, or out to show the subject in its environment. I often go back and forth like this repeatedly every few seconds. I find this much more practical with the relatively small rotation needed with the Laowa compared for example to the Canon MPE-65 which needs a turn of around 360 degrees and then another 90 degrees or so to go from 1:1 to 5:1.
I used achromats for over 10 years with small sensor bridge, micro four thirds and APS-C cameras. In fact for insects etc I used close-up lenses on telezoom lenses in preference to macro lenses, which I did have for micro four thirds and APS-C from quite early on but found I got on better with close-up lenses. I've only switched to using the Laowa setup on the A7ii during the course of the last six months or so, and the only reason for doing that is that with the teleconverter setup I can get much greater depth of field from single-image captures than with my close-up lens setups, which lets me get shots like this (subject around 2mm long) which I couldn't previously (shots like this which have to be single-image captures rather than focus-stacks when the subject is moving around as I photograph it).
I had a little bit of a hard time with understanding this last bit, are you saying that a macro lens gave you a deeper DOF than converted close range lenses or the other way around?
For a given scene, a macro lens can give greater depth of field than a non-macro lens used in combination with a close-up lens.
I have simplified the following a bit to try to avoid cluttering this up with excessive ifs and buts, of which there are some of which the experts will be aware.
The depth of field depends on the aperture you are using, the smaller the aperture the greater the depth of field. With a macro lens (or when using extension tubes, bellows, teleconverters or reversed lenses) the aperture you are using may be significantly smaller than the one you set on the camera/lens. How much smaller depends on the magnification. The Effective f-number (the one you are actually using) can be approximated with the formula
Effective f-number = Nominal f-number * ( 1 + magnification)
where Nominal f-number is the f-number you set on the camera/lens.
(Nikon cameras are an exception to this. Most cameras show you the nominal aperture. Nikon cameras show the effective aperture.)
This means (aside from with Nikon) that if you are shooting at 1:1 magnification and using f/8 then the actual f-number you are using is f / ( 8 * ( 1 + 1 ) = around f/16. Using f/8 at 5:1 magnification gives an Effective f-number of f / ( 8 * ( 1 + 5 ) = around f/45.
On the other hand, close-up lenses do not cause the effective aperture to change as the magnification changes. Some measurements I have done indicate that a close-up lens can cause the f-number to reduce by between zero and 2/3 stop. It varies depending on the close-up lens and the camera lens it is mounted on, but it appears to be fixed for a given combination of close-up lens and camera lens. This means the effective aperture does not change with magnification.
Let's suppose I am shooting a scene at 1:1, and I shoot it with a macro lens and then, with the same camera, I shoot the scene with a close-up lens on a non-macro telezoom lens. As we saw above, with the macro lens set to f/8, at 1:1 I will actually be using around f/16. With the telezoom lens set to f/8 and a close-up lens I will be using around f/8. Since depth of field roughly doubles for each two stops reduction in aperture, I will get around twice as much depth of field with the macro lens than the close-up lens.
However, I could of course use f/16 with the close-up lens, and so I would get around the same depth of field as I got with the macro lens. But suppose I was shooting at 5:1 instead of 1:1. Again as we saw above, with the macro lens set to f/8, at 5:1 the effective f-number would be around f/45. With the close-up lens I probably can't get to f/45. I would probably be limited to f/22. With around f/22 with the close-up lens and around effective f/45 with the macro lens, I would be getting around twice as much depth of field with the macro lens than the maximum I could get with the close-up lens.
In fact, I've recently been using (nominal, set on the camera/lens) f/45 at around 6X or more magnification for shots like the springtail in my previous post. (The Laowa lens is limited to a minimum aperture of f/22, but with the pair of 2X teleconverters the Laowa's f/2.8 to f/22 becomes f/11 to f/90).
So for example f/45 at 7X magnification would be an effective aperture of around f / (45 * ( 1 + 7 ) = around f/360. With a close-up lens on a telezoom lens I would still be limited to a minimum aperture of around f/22. Since depth of field roughly doubles for each two stops decrease in aperture, this means I would get around 16 times the depth of field with the macro lens.
There is however a price to pay for all this extra depth of field. Once you get beyond a lens' "sweet spot" aperture, you increasingly lose detail as the aperture decreases because of the effect of diffraction increasingly softening the image. Using extremely small apertures produces images which are extremely soft and have very little detail, as illustrated below where at the bottom right you can see what an out of the camera JPEG would have looked like for that springtail I posted above, which was shot with f/45 at around 6X magnification. It turns out that if I keep the final image small (I use 1300 pixels high) and I use some extreme post processing, I can get results that I find usable for my purposes, despite their lack of fine detail.
You can of course use focus stacking to get lots of both depth of field and fine detail, but not with subjects like that springtail which was moving around as I photographed it, as are a significant proportion of my subjects.
I don't know how well close-up lenses would work on your 28-75. It is probably not an ideal lens to use with close-up lenses, which work better with telezooms.
After looking more closely at my lens I discovered two odd things.
1. when disconnected from power the iris seems to "fall" to the smallest size, (even farther than it allows it to close when in operation almost)
2. I can't tell for certain but my lens also seems to need power to focus (it is a internal focus) I have not ever run into this before but I have never had a lens that was more then like $200 before so im in new territory)
I think @macrouser has addressed this issue.
