Topic: Taylor Hobson 12.5mm Anastigmatic: Trichia decipiens

Not knowing the effective extension of the lens on the standard M42 adapters, I decided to try a smaller aperture than I used in the first outing for the lens. I wanted a smaller subject than used previously and one in good condition.

Yesterday, I  found just the subject, some fruiting bodied of a slime mould. The DOF at nominal f8 on the lens should be suffient. Having no choice, the FOV was, again, 4mm on the m4/3 and 8mm on the full frame. The lighting was similar, triple flash for the EM-1 and twin for the A7R. I made the mistake of moving on flash too far around the back of the subject for the A7R, giving awful hexagonal flare. I cut much of that out of the top of the fourth image, the others being uncropped.

The images were processed as previously. The aperture is the only significant difference. I had intended to use f8 but the marking on the lens is difficult to see and it was between f8 and f11, the additional DOF being useful, if not essential. The stereo is crosseye.

The results are pretty good. The tiniest difference in focus on the stems of the fruting body can greatly affect the detail, so I am reserving final evaluation. The DOF was just sufficient unless the subject was leaning towards or away from the lens.

The colour is more realistic in the A7R images but I may have use different adjustment for contrast.

Harold

http://www.fredmiranda.com/forum/ufiles/23/1383023.jpg?ts=1480255519

http://www.fredmiranda.com/forum/ufiles/24/1383024.jpg?ts=1480255519

http://www.fredmiranda.com/forum/ufiles/25/1383025.jpg?ts=1480255519

http://www.fredmiranda.com/forum/ufiles/26/1383026.jpg?ts=1480255519

http://www.fredmiranda.com/forum/ufiles/27/1383027.jpg?ts=1480255519

http://www.fredmiranda.com/forum/ufiles/28/1383028.jpg?ts=1480255519

http://www.fredmiranda.com/forum/ufiles/29/1383029.jpg?ts=1480255519

Last edited by e6filmuser (2016-11-30 21:18:58)

Re: Taylor Hobson 12.5mm Anastigmatic: Trichia decipiens

You have improved DOF quite a bit Harold... the images are also sharper.

Re: Taylor Hobson 12.5mm Anastigmatic: Trichia decipiens

JimH wrote:

You have improved DOF quite a bit Harold... the images are also sharper.

Thanks, Jim.

There is a problem with sharpness in images of fungi and moulds. A mushroom is fully formed at the button stage and grows rapidly by being pumped up with water. This does not make for thin layers or sharp edges.

A similar effect applies to some slime moulds, such as this one. Although the expansion may not be so extreme, the very shiny surfaces are a nightmare for focusing, especially with stopped-down lenses. Usually, there are some tiny black specks of surface dust which are a dream for focusing. This lot were annoyingly clean, in theory ideal to photograph but in fact difficult. What I am saying is that, due to this problem,any softness might be down to me, not to the lens. It might do better. That said, the m4/3 images are the best of dozens.

I am making progress towards being able to mount the lens closer to the sensor, enabling magnifications of 1:1 or lower. It is going to be trial and error. In the meantime I hope to find subjects with well-defined detail.

One other observation: I found the full frame A7R much more difficult, the the EM-1, to maintain framing during shutter release. I have encoutered this before. I don't know whether this is a mechanical effect of the shutter (recoil? smile )or a psychological reaction to its very loud noise. I suspect the latter.

Harold

Re: Taylor Hobson 12.5mm Anastigmatic: Trichia decipiens

As has been pointed out to me elsewhere, I have muddled the focal length with that of another macro lens. This one is 12.5mm not 12.5cm.

Harold