Before I try this myself, will I get vignetting on full-frame? I would be grateful if one of you could try that out for me... I still use film until I can cough up the money for a 20D, and I've been researching cheap options for going beyond 1:1 for quite a while. bellyface's conversion looks to be one of the most powerful and especially the cheapest solution out there...
Greetings from the seattle area.... I tried it on my eos 630 and got no vignetting whatsoever. SO it should work. Not sure about the 28-80 or 35-70, I imagine not.
thanks a lot for the information. I guess I'll get one from ePay real soon now... Used 35-80 lenses usually sell for 25-30 Euros these days, but I might get one even cheaper if I buy it together with some antique camera attached (e.g., EOS 1000) ... 8-)
Well, I pulled apart my 18-55mm, and I can't get it to focus - at any given focal length, the middle element stays put. This lens uses the front element to focus.
In this design, would it be reasonable to assume that the *entire* front group is essential to focusing? There several elements in the front group - which ones are essential to fucusing, I do not know. Any ideas? Here is Canon's schematic:
Well, while you were responding to my erroneous post, I was testing out the front-elementless 18-55mm. It turns out it can focus, but the subject has to be just about touching the front of the lens (when the focus ring is fully retracted - which is why I couldn't get it to focus on anything before). So... given that it can focus, any thoughts on that front element group? Is it work trying to chip away at either the front or back glass?
Also, shouldn't a extension tubes increase the working distance? I pulled off the lens to see if pulling it away from the body would increase the working distance and it didn't seem to (of course, trying to gauge the distance to the lens front wile holding the object in one hand and holding the lense in the other with the camera on the tripod wasn't easy, so I could be wrong (yet again).
I'll post my samples in just a minute - I imagine there was some serious shake, as I was either holding the subject or holding the camera (or both), but I think I got a couple still.
The letters are about 1mm in height. Given that each pixel on the 20d is 6.4 microns and each letter takes about 400-425 pixels, each letter takes up 2.7 mm on the sensor. So, at 30mm, the magnification is roughly 2.7x. The shots aren't super sharp, but I wasn't very rigorous and the conditions were far less than ideal.
Any thoughts on what would happen if either the front or rear peice of glass were removed from the front element group?
Also, shouldn't an extension tube set increase the working distance? I tried holding the lens out at a distance, but with my lame first attempt, I couldn't increase the working distance (or at least I couldn't percieve an increase in working distance.
wow... my theory was correct. You get higher magnification with a wider zoom. I'd like to see a full frame version, just to see how much of the frame it fills.
I don't think an extension tube would work unless this is a modified ef-s lens. I think shooting at the widest setting might give you the most distance. I'm looking at the front element and I can tell you that it's gonna be hard to take off... lot of glass... My guess is to take the back one off first... see what that does.
bellyface wrote:
wow... my theory was correct. You get higher magnification with a wider zoom. I'd like to see a full frame version, just to see how much of the frame it fills.
Why would that be? I guess I don't understand the optics enough to know why a wider zoom lens would provide higher magnification.
Instead of showing you the full frame for those images, I'll show you some other samples (100% and full 20d frame):
1) Matches - 55mm f11 (full capture). A few of my shots exhibited some pretty bad flare from where my tripod was set up. Halfway through, I overcame my lazyness and moved it. http://www.wfu.edu/users/pipejw02/photos/web_4781.jpg
So yes, at 55mm, there is some decent magnification. Oh, I just went to make some calcs and realized I read the micrometer wrong - when I said 1mm, it was actually 1/10", so I was off by a factor of 2.54 - which means, at 30mm the magnification is just over 1:1. At 55mm, magnification is approximately 1.3 +/-.
The current problem with using the 18-55mm is that there is only one focal distance. There's got to be a way around that.
Tell me if this makes sense - there needs to be some curvature to allow the lens to focus - I probably won't get near infinity focus without giving up a lot of magnification. Presumably having any glass in the front group will allow for some focus adjustment (hopefully not sacrificing too much in the close range) - so with 5 peices of glass to choose from, it's just a matter of finding a good balance. Of course, on the other hand, you make a good point, if I can't use this with tubes or TC's, perhaps this isn't the best lens to hack away at for macro purposes.
I'll tell you - this is kind of fun, albiet impractacal.
Hey jon, I think I may have found my other better half
These are some pretty interesting observations, It's all a matter of if you are willing to part with your lens situation... I'm sure removing any of these elements will limit your focus to infinity.
If you are feeling experimental, try putting on the front element, but removing the rear. I think that lens is easy to remove, it does have screws there. Unlike the other plastic lenses which are pretty much sitting in a lens molding.
Something tells me this lens determines everything from the back end. Possibly cause it's an 18mm-55mm. If you put it on a full frame you get a circular image, but if you look closely, the angle of view is still pretty wide. I know this has nothing to do with this crazy discovery.... guess I'm rambling....
I'd crack it open, but it's not my lens. Guess I should look for one now
Doing some research here, thinking out loud I guess... according to the specs of the 35-80, if as a standard lens, before mod'ed, it's magnification is .25x, how can we figure it's new magnification strength? Can anyone figure this out?
on another note....
OK, so this lens now has 2 less elements, making it an 8 group, 6 element lens, I think this might be why it is dificult to convert a telephoto zoom lens, even a 35-105. Too many groups, too many elements working to do one thing, make an image
I don't know, but I think I'm really digging this whole new world of estreme closeup!
So I decided to go back to completely removing the front element altogether. The working room was fine, but I noticed a lot more CA, so I ran some tests, looks like with that middle element in place the image was more proned to flair and CA.
So it came off...
I may just crack it off entirely now (so the lens might look a little more pleasing)
I am assuming you are talking about the middle glass piece of the front element bellyface? With the modified 35-70 I haven't had any flair yet. I think the lens is recessed far enough back that the barrel acts as a lens hood. The narrow DOF is the biggest pain, or maybe just the fact that I'm too lazy to setup tripod for my macro shots. .. . handholding and trying to get sharp focus is tough with that lens! I have some decent ones though that I will post to macro forum sometime next week. . . .
