Using the E-M1 converted to full spectrum with the Pinhole Pro objectives is possible. Using a 58 mm NIR filter (Hoya R72) attached to the front of the 11 mm Pinhole Pro S11 worked fine, with no increase in vignetting. Using the StraightEdgeU 52 mm or Baader U-filter 2″ with a step-down ring blocked the corners of the image completely. The original 26 mm Pinhole Pro suffers a lot less from vignetting and can be used with these filters of smaller diameter than the front thread of the lens without problem.
Pinholes need to be very small to provide a useful image. Consequently the corresponding f-values are small, in most cases f:100 or smaller. This results in either very long exposures, or requires the use of very high ISO values. As we will see in the example images this is less of a problem than what could be expected because as the resolution of the pinhole is low, the images tolerate very strong noise reduction processing without losing there character or mood.
I have been testing some objectives for their UV transmission using LEDs as sources of radiation. I developed a protocol for such tests. Although used in this example to measure the spectral sensitivity of a camera sensor, the protocol can be easily adapted for the measurements of biological action spectra.
For those interested in photography “beyond the visible”, some of the filters available from Midwest Optical Technologies Inc. under the MIDOPT brand name should be very interesting. They are distributed in European countries by Stemmer AG. Both companies are specialised in the supply of machine vision equipment. What adds additional interest is that filters are supplied in very many different sizes (from M13.25 all the way to M105, mounted and unmounted, and even with mounts suitable for installation at the back of objectives with C-mount).
Here are three examples of time lapse videos captured in the absence of visible light. Two videos were captured under ultraviolet-A (UVA) illumination and one under infra-red (IR) illumination.
Many cheap extension tubes, lens adapters and lens hoods are made of aluminium and have a black anodised finish: are they always better than plastic ones? As it was revealed by the macro extension tubes comparison internal reflections can be a problem in visible light and lead to glare and low contrast. These problems are caused by a relatively small amount of visible light reflected by anodised aluminium, specially if the surface is smooth. The ribbed surface frequently used avoids specular reflections, so controlling “stars” and similar artefacts but not so much the loss of contrast due to diffuse reflection. Continue reading Black anodised aluminium in IR
Depth of field is the depth region that looks in focus in a photograph of a three-dimensional object or arrangement of objects. Consequently, we discuss here how and why DOF is not absolute. Continue reading Depth of Field (DOF)
An on-going Kickstarter campaign offers sophisticated pinholes for digital cameras in an assortment of different lens mounts. I ordered mine, as I am interested in ultraviolet photography and pinholes, in spite of their many limitations, allow radiation of any wavelength through. Pinholes are simply very small holes in a thin plate.
When travelling by train, bus or aeroplane we frequently see views that would make great photographs. In this post I display a selection of pictures I have taken through windows while travelling in Finland between May and October 2017. I also explain some tricks-of-the-trade that hide or attenuate the effects of the optical imperfections of windows. Continue reading Photographs through windows
High dynamic range (HDR) is used to refer to photographs which have captured a broader range of luminosity values than what is usual. In most contexts it implies a higher dynamic range than a digital camera sensor can detect between saturation and its noise floor. How can this be achieved? By combining several images so that different parts of the scene come for images taken with different exposure settings. In other words exposure bracketing followed by digital processing to merge the images. If you do not know what is the meaning of bracketing in photography please first read my earlier post on the subject. Continue reading High dynamic range