Using Close Up filters as Wollaston Meniscus lenses

[Ian Grant]

Has anyone here tried it. Andrew O'Neill has posted a Youtube video on using a Wollaston lens, a single element and identical in shape to a close up filter.

I have a Compound #3 shutter with flash sync, it must have had a front mounted lens, no idea what though. I figure I can use it with Close up lenses as a Wollaston meniscus lens, giving me a shutter, but more importantly aperture control as well.

A Hoya +2 close up filter covers 10x8, and has a focal length of around 21" / 530mm. I have a new set on the way, +1, +2, +4, & +10, I think the +4 will be the best to use for 5x4 work.

Incidentally, a +2 cu filter on a 12" Dagor focussed at Infinity alter the focal length to approx 8", greatly increasing the angle of coverage. Also increasing the f-stop from f6.8 to f5.1, about 2/3 of a stop. This is an observation rather than something I would use.

Ian

 

[Petrochemist]

Not something I've tried yet but I've been meaning to give them a go.
Of course most close up filters are not achromats so will display significant chromatic aberration. My thought was to try my Raynox lenses (which are 3 element achromats) then a simpler lens for UV photography where the more restricted wavelength range will limit chromatic aberration...

Interesting to hear the coverage confirmed, I'd assumed it would be good but have never checked

I'm sure you know but for the benefit of others reading this thread focal lengths are roughly 1000/diopter (the + number most close up lenses are described by)
+1 = 1000mm
+2 = 500mm
+4 = 250mm
+10 = 100mm

The Raynox DCR lenses are +4.8 (208mm) & +8 (125mm)

Knowing how I progress my projects it's likely to be at least 10 years before I actually try the UV photography, due to complications like focusing!

 

[Ian Grant]

The +4 is indeed 250mm, the filters arrived a few minutes after posting the thread. The +4 looks good on my 10x8 screen, but clearly would only be useful for 5x4, perhaps 7x5 for close portraits, after that sharpness drifts off significantly.

Ian

 

[Pete Spencer]

I haven't used a closeup lens but did once make a large format lens out of a +4 dioptre meniscus lens. I housed it in a strange, flanged brass tube I found. The lens was cemented in the housing, about 50mm inside diameter. I made some Waterhouse stops out of black card after calculating the stop numbers. As expected the pictures, on 5x4 were pretty sharp in the middle and staggeringly fuzzy towards the edges.

 

[Graham Patterson]

I have a Copal #0 shutter with the lens barrel from a defunct 135mm lens mounted on the back. This gives me a 49mm close-up mount with the flat/concave face towards the subject. Because of the shutter the effective aperture is limited to about 22mm wide-open (the shutter opening less the cut-off from the shutter depth). This also provides a hard limit on the angle of view. Naturally the aperture scale on the shutter has to be calibrated for the lens in use.

Playing around I found I could use +3 or more on 8x10 (333mm), +4 on 4x5 (250mm), and +10 on 2x3 (100mm) and get decent illumination over the frame. Without the shutter I could go a bit shorter in focal length and get illumination. I can also go a lot longer if the camera can handle it.

I actually tried +14 on my 2x3 (71mm), and got an illumination of about 75mm (shutter housing limited). I calculated it out to a theoretical 106mm diameter, I think, which shows how much effect the #0 shutter contributes.

Using a yellow or green filter cuts down on the chromatic aberration, and stopping well down keeps the un-sharpness bearable. Not an everyday lens, but it is low bulk and weight compared to all the other LF stuff - like my pinhole mount - and just lives in my filter case.