I posted this on a couple of sites where I received a lot of requests to share my technique and settings for the reversed 50.. I am posting it here for you guys so that if you decide to give it a go you have the info too.... Take care....Alex
First let me say I am no self proclaimed expert at this stuff but I have been getting a lot of requests to explain how I am using the reversed 50 set up....Most of us have seen outstanding Reversed 50 work and I, like the folks who are now showing an interest, decided I had to try it out... I have learned a few things a long the way, and this is to share what I have figured out while attempting to get good at it....My hope is that in sharing what I do to get the results I am achieving you will be smoking me shortly, and others who are succesful at it might throw in some useful tips that will help all of us improve..... My set up consists of a 70-200 f4 Canon lens with a reversed Nikkor 50mm f1.4. I made my own adapter to reverse mount the 50 but I don't recommend wasting the time as they are cheap to buy and I am sure more solid.... Here are 2 sites that sell the adapter ring sets and also have some more good info you should read.
http://www.kirkphoto.com/polarizers.html
http://www.camerafilters.com/pages/macrorings.aspx
You are connecting the 50mm and what ever main lens you are using, filter thread to filter thread by way of the rings from the above sites....
In shooting the rev 50 set up you must get the flash out to the front of the stacked lenses as working distance will usually be 1" or less. Needless to say a hot shoe mounted flash won't squeek in where the light needs to get with so little space....Sooo... Off camera flash adapter chord is a must and you will need a good flash bracket as well.... I am currently liking the Manfrotto macro flash bracket as it seems to have plenty of adjustment, though at times I wish it was a bit more rigid but it works fine...I also have 2 different flash units. 1 MT-24 and a basic 420 with Stofen diffuser. I just use the basic 420 on the bracket for the rev 50 setup because the MT needs to be rigged and I hate using tape to hold the flash head mount on which I have done but it sucks.. When hand holding your shots this will be what you want. When tripod shooting I usually remove the flash from the bracket and take 3 shots essentially bracketing by changing the flash angle and location to see what is most effective.... Focusing can be a real challenge because you are shooting in manual mode and that includes focusing..... (Be sure any auto focus function is turned off on your lenses). If hand holding indoors I usually have a good bright room light on.... If tripod shooting I will often times use a flashlight to illuminate the bug to hit "perfect" focus, and then turn it off and start shooting.... I assume some people use other means for all of this stuff, but I use as little as I can get away with .
The basic lens settings..
If you have a manual 50mm you will set the lens aperture wide open.. If auto, mount the lens to camera, turn the camera on and adjust aperture to wide open. Turn camera off and lens will remain at that setting... Remove lens and mount to main lens..... The aperture needs to be wide open to help reduce vignetting, and with lenses stacked it is a plus that it lets as much light in as possible . I have no experience shooting a prime lens as my main lens and so can only share my experience using the 70-200 zoom... My guess is any main lens that is capable of 65mm focal length or longer will work well for that up close and personal outcome..
I leave the 50 set up at minimum focusing distance and never use it to focus... "Set it and forget it"... I use the focusing ring on the main lens occasionally but usually achieve focus moving the lens in and out. If I am using tripod I will use the focus ring if I am really close to focus and don't want to mess with moving the tripod as I don't use a focusing rail.... Main reason is bugs move and the less to fiddle with the better IMHO..
What I have found I really like about using a zoom lens for the primary lens is it allows you to frame the shots. 70mm gives a wider view and many times you can get a bug profile shot and get most or all of the bug in the frame. When you want to shoot for detail on an eye, a Midge, aphid, or some other dust speck size bug you can zoom right up to 200 and count the number of dingle berries if you are so inclined ... The flash I leave set on ETTL, with High Speed Sync and it seems to adjust pretty well....
Typically I start with the following settings if hand holding... ISO 200, f11 and shutter speed 250. I take a couple of test shots to see how the exposure looks and adjust as need usually adjusting shutter speed, but not going below 160...If still under exposed I will take aperture down to f5.6, but keeping in mind the DOF gets reallllly thin at about that point.... Final step is jack the ISO if needed....The adjustments priority changes if DOF is a prime consideration...... You do need to experiment to find what works best for the shot you are going for.....Quite often for me the sweet spot seems to be :ISO 100 f20 to f22 and shutter speed 250 to 320. I will shoot as high as f 29 with ISO cranked to 1600 if I want to shoot more depth than just a profile or a detailed surface shot but..... It will give some vignetting and the shot has to be cropped to get rid of it.....
Another critical thing I can think of is you need to pay close attention to the angle at which you are shooting.... If you don't get the lens squared up to the bug you will have one part in perfect focus and the rest of the frame way out...Get squared up when possible.....A good way to practice in the beginning is to get bugs that don't move around much and set up a stage on a kitchen counter (Or whatever is handy) Get some leaves put them on a cup saucer, or Tupperware lid and place the bug out toward the edge.... You can get your rig dialed in fairly easily when you control the stage which with this set up you have a good chance that you will...Flash placement is also key to good shots.... You can also get comfortable with the set up using a pin or other small object to practice focusing technique before trying for things that like to move.....
When possible shoot with flash at different angles and distances.. Check the LCD screen when you can to see if you are looking pretty good..... I shoot Jpeg and don't use the histogram I just look to see if it is looking good, or if it doesn't. To calculate what magnification you have with your particular lens combination you take the focal length of your primary lens and divide that by the focal length of the reversed lens.ie: 200mm divided by 50mm equals 4x or 4:1 magnification.. 4 times life size gets really interesting...I hope this made sense and that it helps get others going on the fun of the Rev 50.....
Once you get the hang of the settings and basic technique it is very cool to see the detail on the reallllly small things.......If I have missed an important step or if anyone has tips to add to this post please feel free.........Take care....Alex