Meniscus (DIY)

enzodm · Joined: 11 Sep 2010 Posts: 350 Location: Italy

Following the request for a kick in the pants, I put here instead of the lenses forum my new hack. I bought a concave-convex lens on Ebay, 16mm diameter, 25mm focal length (declared), and applied to a E-P1 with some quickly made sort of mount so ugly that I do not want to show it (to avoid real kicks Wink

).
This follows my attempt of reusing a disposable camera lens: http://forum.mflenses.com/silly-rainy-day-project-disposable-camera-lens-t57852.html .
Real focal length resulted in something around 13-14mm, however since there is no mirror, I managed to put it recessed, although I did not have yet the bravery of reaching infinity.

Anyway, results are as follows (with some cardboard iris: around f/2 the first if I remember well, and f/4 or so the latter).

RSalles · Posted: Fri Apr 12, 2013 4:23 pm Post subject:

The second shot is terrific, scene made for this lens,

Renato

GrahamNR17 · Expire: 2012-09-06

Wow, such a dreamy effect. The flower and the baby work really well for it Cool

SXR_Mark · Joined: 12 Jun 2010 Posts: 506 Location: England

I really like the dreamy effect in the first picture. I actually find the picture of baby's face rather disturbing, Because the chin dissolves into blur, I see the face as detached, as if it has been cut off. Shocked

Before photography was invented, Wollaston discovered that a simple meniscus lens gave a much flatter field than a simple biconvex lens when used in a Camera Obscura. The disadvantage of the meniscus is worse chromatic aberration, which was problem for early photography as it meant getting the best focus was difficult. (Daguerrotype plates were sensitive to blue light but the eye focussed with the green part of the spectrum). You could try converting to greyscale using just a single colour channel (equivalent to using a colour filter on the lens) to see how that affects the sharpness.

Did you have the convex or concave surface facing the subject? You can try either way around. Wollaston had the concave surface in front and placed a simple stop in front of the lens to reduce the aberrations (a lot of spherical aberration).

Mark

enzodm · Joined: 11 Sep 2010 Posts: 350 Location: Italy

Mark: thank you for the infos, in particular the possibility of reverting the lens. I'll try soon (now is convex to the subject).
I have yet to try b/w, and I confirm that there is a lot of spherical abherration.