A new line of Chinese pictorial lenses!

[Mark Sawyer]

Tim's got it. Focal length is just the distance from the lens to where it focuses. And if you calculate the f/stop by dividing that focal length by the aperture's diameter, you can forget all that bellows extension stuff. You'll know the actual f/stop you're using.

[Øyvind:D]

I have tested step down rings and close-up filters in Copal #3 (and #3S used in Fujinon, Computar etc). None fit because the 58mm (56mm on #3S) filter threads start further in than on a lens or a filter ring. The solution is to buy a step down ring from SK Grimes. I bought two for my Ilex #5, front up to 77mm and back down to 72mm. This way I can use a +2 Canon close up lens mounted back or combine it with a +1 in the front to reduce focal length (and increase aperture). Here is the pricing of these threaded adapters if you dont want to tape the close up filters in place: http://www.skgrimes.com/products/adapters

[Øyvind:D]

Here is example of bokeh of +2 achromat Canon and a +1 no-name http://www.flickr.com/photos/47052585@N06/9442603334/

[Øyvind:D]

As you can see the +2 Canon 500D close-up lens has a close to perfect bokeh mounted behind the aperture. These are photos of the ground glass only: http://www.flickr.com/photos/4705258...n/photostream/

[Øyvind:D]

I find the bokeh of the +4 Canon 250D really cool: http://www.flickr.com/photos/4705258...n/photostream/

Note: all bokeh pictures are focused and then extended 10%

[rpa]

So I ordered some cheap eyeglasses from Zenni Optical (recommended _if_ you exactly know what you want) and also extra round frames with +4 and +3 lenses for $10.

Chinese +4 eyeglass lens (plastic meniscus) taped behind aperture convex side forward. Fomapan 100, 15s ~F22. D76 stock 8min (in Paterson Orbital).



Wut?

[Tim Meisburger]

Fun stuff! So you just tape the lens to the back of a shutter from which you had removed the lens elements? Good idea, as then you have aperture control and a shutter!

Try it outside next time. I think you will like it.

[Patrick13]

This is the best thread on the internet.

So many ideas!

[ruilourosa]

Achromat close up lenses work quite well, specially in combination, one on the front and one on the back, i find identical individual focal lenght of the elements work better than different, i am using minolta achromats an leica elpro, the main problem is price... achromats are expensive...

i had excellent results building a +- 500mm with two +1 close up lenses in 77mm,

Check the rapid rectilinear and steinheil periskop lens formulas

i am building the lens barrels out of rings of cheap uv filters (i broke the glasses)

i am in an experimental level and have no need to use shutters, but in the future i will have to consider that...


cheers


rui

[Mark Sawyer]

It's nice to see this thread pop up again! For those interested in mounting those simple close-up lenses into shutters, here's a link to a page with the common shutters and their front and rear thread sizes:

http://lensn2shutter.com/shutters.html

There are also a number of these lenses made as achromatic doublets. Here's a pretty good list of options:

http://fuzzcraft.com/achromats.html