Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
1 Like  
deep into some flowers at 2:1 and 3:1 macro ratio
Posted By: Douglas_of_Sweden, 08-15-2010, 11:21 AM

Putting a reversed short lens in front of a longer lens is a good way to get beyond 1:1 macro ratio. But it eat light, of course. So when I got the AF160FC ringflash I was curious to see if it was compatible with the reverse ring light holder K to put a ring flash to the mount of the lens (thanks Diminotrov). And yes, it is.
But like before, since you with most lens configurations end up very close to the subject, the ringh flash is of course also very close to the subject. Sometimes it only iluminates the background (which can cause a nice siluete effect). Anyway, here are some shots I made just in the beginning of my vacation, putting either the FA35/2 or the FA50/1.4 reversed in front of the DFA100/2.8 macro, which should give magnification ratios of about 3:1 or 2:1.

First, with the DFA100 set to f5.6, to demonstrate how extremely thin the DOF is (in the later shots, I've closed down more, but the DOF is still very thin. You can't work against this, so one have to use it instead.


Stammen of some flower


Stigma of some other flower. The small "balls" are pollen. Appears as if bee's & Co have left pollen from different plants. Is that a pollen tube forming from one of the pollen near the center of the photo?


Same flower with the focus on the fillaments.


Different flower, more fillaments.


Actually forgot what part this is , but it is hairy...


I think this is part of a very tiny flower (a few mm in total).


Part of a flower petal someone found to be tasty.


Inhabitant in the same flower, perhaps the hungry one?

Views: 3,606
02-27-2012, 02:24 PM   #16
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
QuoteOriginally posted by margriet Quote
I have a question about these magnification ratioīs...
You say 100mm with 50 reversed gives 2:1 and it doesnīt matter of you use 100mm macro or tele. But where does the difference in magnification between the last two go? I just canīt believe it wonīt matter if you use a 100 1:1 macro or a 100mm 1:2 or 1:4.. but hey, I like to be eye-opened if you can explain this!

Your pictures by the way are top! I have been experimenting with 100mm macro and tele / macro converter 3x, the world of small things is getting bigger and bigger But as you say, it takes a lot of light and even with flash searching through viewfinder in dark places can be madness on the eyes.. you got any tips about this?

regards, margriet
Here's what happens, one step at a time...

The magnification of a lens on a camera follows a simple equation:

m =( distance.to.sensor)/(focal.length) - 1

When focused at infinity the lens is exactly one focal length from the sensor and m is 0. When the lens is 2 focal lengths from the sensor the mag is 1x, etc.

You can increase the mag either by increasing the distance to the sensor OR by decreasing the lens focal length.

When two lenses, with focal lengths f' and f" are stacked close together they form a new lens with a new focal length, f, equal to:

f = f' f"/(f' +f")

Say you put a 100mm macro lens focused at infinity on the camera, the mag is zero; M = 100/100 -1 = 0

Now say you put a 50mm lens in front of the 100mm lens. The new focal length is 100*50/(100+50) = 33.3mm, but the distance from the sensor to the lens still hasn't changed from the original 100mm so:

m = 100/33.3 -1 = 2x

Now if you turn the focusing ring on the macro lens, it will move farther from the sensor or sometimes the actual focal length of the 100mm lens will decrease, or both; this will further increase the magnification. The extent of extra mag you can get depends on the maximum mag for the original 100mm 1:1 lens and how it gets its magnification (extension (5x) or focal length decrease (3x).)

Putting a 3x Teleconverter on the rear of the original lens multiplies the focal length by three but also increases the f-stop by a factor of 3, which decreases the brightness by a factor of 9! Putting a closeup lens on the front of your camera lens does not change the image brightness so can be much easier to work with.


Last edited by newarts; 02-27-2012 at 02:38 PM.
02-27-2012, 04:10 PM   #17
Site Supporter
Site Supporter
Douglas_of_Sweden's Avatar

Join Date: Apr 2008
Location: Stockholm
Photos: Gallery
Posts: 3,374
Original Poster
Thanks everyone, I think I got more comments now than when I posted the picture some 1 1/2 years ago. And thanks Newarts for the excellent explanation. I was afraid I would have to do it myself

Summer coming I hope I will post some more with these magnification ratios, but now not with stacked lenses (or as in another thread cheap microscope lenses) ,but with the Canon 20mm f3.5 micro lens built for 4x to 10x magnification. I picked it up for a good price a while ago. It mounts on royal microscope threads (RTM) so with a cheap RTM-K adapter I use it on either bellows or tubes. The advantage to the microscope lenses is that it has an aperture mechanism and can be closed down for a little bit more DOF and better contrast etc.
02-28-2012, 02:13 AM   #18
Senior Member
margriet's Avatar

Join Date: Feb 2012
Photos: Gallery | Albums
Posts: 191
Thanks very much for the explaining! I know itīs not easy to do this. I will check my macro lenses to see whether the back lens goes into the lens when focusing, which is the way to see if itīs extending or decreasing I think.. Youīre (newarts) comments about brightness decreasing is duly noted and will probably join the club of stacking lenses.
Douglas, so weīll see more magnification from you in the summer! I think this 20mm lens sounds also really interesting!

regards, margriet
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dof, flash, flower, front, lens, macro, photo, pollen, ratio, shots
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Crop Factor and Macro Ratio GregK8 Pentax SLR Lens Discussion 45 08-13-2010 12:49 PM
Magnification ratio in macro photography ntx Pentax SLR Lens Discussion 7 08-19-2009 02:22 PM
Macro Flowers metroeloise Post Your Photos! 10 11-24-2008 07:36 PM
Macro Flowers photomad_2007 Post Your Photos! 1 06-08-2008 06:00 PM



All times are GMT -7. The time now is 02:38 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top