Below is a copy of a post I just made on POTN forum. The question here is is this correct ? Brian V. Following a discussion here http://www.dpreview.com/forums/post/56372729 started by user SteB on odd DOF effects using an add-on diopter. I did some DOF tests with my sigma105 lens at infinity focus ...

vendav wrote:Why bother, there's plenty of crap there already.

Brian v.

Not sure what managed to do this rather clever poo on a dustbin lid - taken at 4.8:1 and focus stacked. It is standing up on one edge. I did wonder about taking it to the Tate modern
Brian v.

Thanks for the discussion.
Can only say I was surprised at the result- it certainly does something that I can't do with just simple USM use.

Brian v.

I use canon's DPP raw converter (still using the v3 series but v4 has DLO as well). Yesterday I came across a thread on dpreview that commented that canon says that using DLO can reduce diffraction in shots. This sounded a bit far fetched to me but I decided to try it out. 2 shots below a bee have b...

I've just tested the ETTL flash camera behavior with my 7D and I think I could have found the possible reason: The measuring preflash is done with the diaphragm wide open* and the diaphragm just closes for the actual exposure, so the camera needs to compute the lens aperture. If the actual effectiv...

Thanks Rik for the comments and info- yes not really new stuff but it was an awful lot cheaper than the novoflex and worth a play. It also does seem pretty well made and comes with 58, 67,72 and 77mm adapter rings

Brian V.

First few goes with this adapter which can either be used as an odd electronic extension tube or as I was using a lens reversal adapter that maintains full electronic control of the lens. Tried it with the kit lens. One oddity I noticed during shooting with ETTL flash was the shots were around 1 sto...

For all lenses, the effective f-number means the same thing in terms of DOF and diffraction. But lenses vary in how the effective f-number depends on the f-number that is set on the lens, especially when reversed and extended. This does depend on the pupil ratio. See FAQ: What is "pupil ratio" and ...

If I reverse a lens does the F-number mean the same thing in terms of DOF and diffraction. I assume it does not necessarily mean the same thing if the entrance and exit pupil are different ? This question came up as someone thought the DOF of a reversed canon kit lens at a set aperture was thinner t...

Brian, it's good to see you back here after a couple of months' absence. The images look rather better than just "useable", but I'm accustomed to seeing that with your lens combos. In this case the numbers make good sense. Cranked out to its 5:1 end, the MP-E 65 acts something like a focal length 4...

Well it was raining so I decided to to see if I could get an image using a Raynox MSN-202 +25 dioptre on the front of my MPE-65. I didn't hold much hope but to my surprise I did get a useable image with the MPE at 5:1. The magnification though was more than I expected at near 9:1 instead of around 6...

Interesting stuff Chris !
Brian V.

Just a follow up. Looked at quite a few webs yesterday around lucnchtime in fairly bright sun and could not really see much in the way of colour effects. This morning though got the photo below shooting into a tangle web nearly directly into the low early morning sun. Certainly showing some optical ...

I'm pretty certain I've only seen this effect in strong sunshine.
Brian v.