Over in the POTD thread S3000 commented on my Minolta Macro Lens and I thought a new thread discussing Macro might be worth while.
So, here's a pic of my Minolta MD Macro Lenses.
Originally Posted by S3000
On top, my Minolta MD Macro 100mm f4 Lens and matching extension tube and Hood alongside.
Below, the 50mm f3.5 Lens. The lens is fully extend and extension tube alongside
The "White" scale is for 1:2 magnification, that is to say, half size (or quarter size depending on definition).
The "Cyan" scale is for 1:1 magnification, that is to say, Full Size (by any definition).
The big difference between the two lenses is "Working Distance" and "Perspective".
For instance, for 1:1 magnification, the distance from the front of the extended 50mm and the extended 100mm lens to subject is 50mm(2") and 200mm(8") respectively.
If you fit the Hood to the 100mm, then the distance is reduced by some 60mm(2.5").
That 50mm distance can frighten away little creatures especially if the lens casts a shadow over it.
Worse still using AF to focus, the noise coupled with the expanding lens front can be enough to trigger the flight reflex.
That leaves perspective which is quite different for the two focal lengths and largely a matter of taste. No doubt those of us who chose a 50mm will argue strongly in its favour whilst the 100mm Brigade will be equally adamant of its virtues. It's my good fortune to have both so I fall between two stools but the truth is, they both have their pluses and minuses. I chose the 100mm for my recently posted Insect Macros simply because of "Working Distance" but for most plant/flower shots I prefer the angle of view of the 50mm lens. It gets close enough to avoid front clutter and gives that feeling of being really close. You "pays yer money and takes yer choice" as they say.
Oh yes, I nearly forgot about the cost. The Sony 50mm Macro will set you back £350 and the 100mm Macro £500. Ouch!
Or you could go Tamron 60mm, 80mm, 180mm at £390, £344 and £700 respectively. Once again, Ouch!
I mustn't forget the Sony DT 30mm SAM Macro at £160, however the working distance for 1:1 is around 19mm. Hmmm!
Both my lenses are 30 years old but fully functional and of course, manual focus. I don't count that as a negative because I find AF Macro lenses fail to do the job most of the time and are excruciatingly slow and noisy especially when the lens racks all the way out and back again. I did purchase a Mino 50mm f2.8 Macro with the intention of replacing the old ones but in the end got rid of the AF lens. I might have a different opinion if the Macros doubled as normal lenses as well but, in my case, they don't. I have no personal experience of any other Macro lens.
As it happens, I've had these two venerable lenses for donkeys years but a big plus today is the price. You can find good examples of the 50mm for £30/£40 and perhaps two to three times that for the rarer 100mm. You also need to factor in £15/£20 for an adapter to allow the MD mount to fit an A-mount
There are other cheaper options to try:
Macro Converter (seven-element 2x converter from Teleplus)
Zoom with macro function.
None of these is as good as a real Macro lens which is designed to perform best at high magnification and some of the options are a bit cumbersome but good results can be achieved.
Of course, you can simply use a long Zoom Lens, however, that will give you something like 1:5 magnification which is not true Macro, depending on your definition of the term. It used to mean "at or near full size" but now there seems to be more latitude.
Here's a 50% crop of a Red Admiral taken with a Minolta 200mm G lens.
Nice image but "Macro it ain't" and it has been cropped to quarter full size.
Also an uncropped Red Admiral with 100mm Macro.
This pic gives you an idea of the different sizes of 1:1, 1:2 and 1:5.
The big bugbears of Macro Photography are low light levels, Focus Accuracy and limited DOF (Depth Of Field).
Lack of light is always a problem at Macro Magnification. First off your f2.8/3.5 will be more like an f4/5.6 when its fully extended with attendant light loss. If you can get your subject in full Sunlight without casting a shadow, that's great, otherwise you may well need some flash assistance. Make sure you diffuse the flash or you're going to suffer from specular highlights. No need to spend a fortune, a homemade one will fit the bill nicely. I used a double diffuser for the shot of the screws.
In terms of easier (manual) focus acquisition, Pentaprism VF's are better than Pentamirror but the cheapest Sony with that is the A700.
Now that I have the A900, accurate focus is helped by the excellent OVF but changing to the M-screen would be better.
I've never owned a Live View equipped camera but that would definitely be a good way to achieve critical focus although I have my doubts about Bright Sunlight.
The A55 (A77?) may bring something entirely new to the Macro table. As far as I can tell, using the focus magnifier, you can get up to x15 magnification in the EVF (or rear LCD). That could prove to be a major plus for Macro work.
As an aside, here's an interesting use of a 100mm Macro with the A55.
Next up for scrutiny is the pitiful DOF (Depth Of Field). At these high magnifications, there isn't any (well hardly any).
Here are some pics of a couple of screws and a tape measure using the 100mm f4 Macro at full extension, i.e. 1:1 magnification, on my A900.
The screw head diameter is 8mm and the overall length is 9mm.
First pic is the whole frame and next are crops at various apertures.
You can see that f4/f5.6 are practically useless with a DOF around 1 or 2 millimetres.
Even at f16 the DOF is still only 7 or 8mm and diffraction degradation is visible.
You can forget DOF (Depth Of Field) in terms of Focal Length selection or Sensor size. At the same magnification and F-stop the DOF will be the same on whichever lens you choose. The Purists will now say that the last statement only works if the lens is of symmetrical design where the "Pupil Magnification Factor"= 1. This may come into play with a 200mm FL but at true Macro magnifications is still irrelevant IMO.
BTW, at these magnifications the DOF in front/behind the focal plane is exactly the same (the far DOF only lengthens with less magnification).
Here are uncropped pics using the A700 first with the 50mm Macro, then with the 100mm Macro.
Although switching to the the A700 will not affect the DOF, there's a big difference in image size.
This is an uncropped A900 frame with an uncropped A700 frame overlaid.
The vignetting is from a rather poor adapter overdue for replacement.
Sometimes you just have to pull the magnification down to get a (barely) sufficient DOF.
Here's a picture I posted in POTD but illustrating the crop used.
That's quite a big crop, 24MP down to 8MP. Try that with the A700 and you'll end up with a 4MP image.
Of course, although Focus Accuracy and DOF are separate issues, they go hand in hand at these magnifications.
You can see that the far wing is in reasonable focus as is the front wing although the wing tip is disappearing.
If you leave focus acquisition up to an AF lens, you have no idea whether it will focus on the edge of a Wing, a body hair or whatever. In any case, and yes I've said it often, the AF is not that accurate and the lens is likely to front or back focus which is another reason to prefer manual focus.
Whatever happens, anything that helps with accurate positioning for critical focus is a bonus. The ideal scenario is that you're using a stable tripod with a macro rail which gives 6" of movement in both horizontal planes.
With this setup I rack the lens out to the desired magnification factor, focus using the "rail" and fine tune with the focus ring; or whatever works. That's fine for a static subject but, for an insect, requires that you have prior knowledge that the creatures will be there, like for instance a rotting apple on a tree.
Other than that I use a monopod fitted with a quick grip ball head, or nothing at all.
Monopod with quick grip ball head
Again, rack the lens to the required magnification and then fine tune by swaying backwards and forwards until you get the required focus. If it sounds awkward, it is, but when it works...
Seeing as I have A700 and A900 cameras, my comments are largely based around those two. I mentioned the big advantage that accrues from having the larger frame of the A900. Basically you can crop away half the pixels and still have an image the same size as an uncropped A700 image. That's a big advantage and allows you to give up some magification to the benefit of DOF. The recent release of the 16.2MP sensor brings about a similar benefit to APS-C. The A55 has a 32% greater photosite density than the A700 so you could afford to sacrifice some of that gain in the interest of DOF. There are rumours that the A77 will have an 18MP sensor implying an ever bigger increase in density to 50%.
If an A77 with 18MP turns into fact, the extra density coupled with the EVF magnification could make that camera hard to resist for Macro work. Unless they release an A99, in which case.....
I guess there's more to say but I've run out of steam for the moment, need some sleep.
Comments and contributions welcome. Donít be afraid to stick your head over the Parapet.