Tag: lenses

Hemispherical time-lapse under a tree

In two earlier posts titled “Lens adapter with filter drawer” and “Lens adapters: flange-to-flange distance” I discussed how crucial it is to achieve the exact effective flange-to-flange distance when dealing with adapted objectives with a very short focal distance. I also described how I shimmed an adapter to achieve this.

Recently I had an opportunity to use the Sigma 4.5mm 1:2.8 circular fisheye objective in Nikon AF mount adapted to my Olympus E-M1 Mk II camera to create a time-lapse video. I captured 500 images, with a pause of 1 s between them. Total time was a bit over 10 min as capturing each of the images did take a fraction of a second. The lens and camera performed very well.

The first image in the sequence of 500, RAW image converted to a reduced size jpeg file in Capture One 20. Click on the image to view the video at Vimeo.

Lens adapter with filter drawer

I here describe my experience with the DEO-TECH OWL EF/MFT lens adapter. The adapter is available mainly through astronomy web stores and seems to be currently distributed by Optolong. It is also available on special order at B&H photo video and possibly other large shops. Development of the adapter was initially  funded through Kickstart crowd funding.

DEO-TECH OWL EF/MFT adapter

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Digital UVA-photography with M43 equipment

How far can we go, with off-the-shelf equipment

One question which I have been pondering for some time is: do I need to have a digital camera converted to full-spectrum for UVA photography? and are there any modern objectives that are good accidental UVA-objectives?

This is not a question of cost alone. Although a converted camera can be used for VIS photography, obtaining good colour reproduction requires effort. A suitable filter is used on the objective to replace the one removed from the image sensor unit during conversion. As it is not possible to find a perfect match to the filter removed, one or more colour profiles of the camera need to be created and applied instead of the one used automatically by the camera and/or raw file converters. So, in many cases, for best results one would need to carry two different cameras to any field trip. In addition a conversion voids the camera manufacturer’s warranty and even access to official service facilities. Continue reading Digital UVA-photography with M43 equipment

Pinholes in NIR and UVA

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.

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Pinhole objectives arrived today

Introduction

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.

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Camera objectives for UV photography

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.

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