Tag Archives: Tilt-shift

Focus Stacking, Part 2: Artefacts

Now as part 1 of this post has had time to settle, let’s press on. Focus stacking is one of the techniques know as Computational Photography, which include panorama stitch, high-resolution sensor shift, multi-exposure HDR, and light field. All these techniques involve multiple images that are blended in post-processing to a new type of single image or scene representation; opposite to techniques in digital photography that work on a single capture, such as filtering and color adjustments.

These techniques may promt the question about ethics in photography. I have absolutely no problem with time-lapsing out people, for example. Over-saturation and over-sharpening, or turning the colors of a lake in Scotland to those of the waters at Anse La Digue is another matter. And nobody would consider the surrealistic photo-illustrations of David LaChapelle as dishonest work, while this is exactly what Steve McCurry, or his now fired assistant, are accused of producing. In my oppinion the problem lies not in the image itself, but its (incoherent) caption and the (false) message that the image is supposed to support. But I am digressing.

Focus stacking is particularly useful in situations where the scene has a large range of depths in the subject space compared to the shallow depth of field obtained for a given sensor size, focal length, and aperture combination. It will also be a way to make sense of the future FF sensors with 50+ megapixels, where diffraction will counteract the increase of accuaty by stopping down and compromise image quality for depth of field. Moreover, focus stacking can be useful to reduce noise in astrophotography. So there is nothing dishonest here; it is an attempt to optimize the conflicting elements of image quality:  noise, diffraction, lens-aberations, and depts-of-field.

There is, of course, the alternative of using tilt-shift lenses, but this is constrained to inclined focal planes (continuous depth maps), for example in landscape photography. The subject of the image below would also qualify.

gitarre-ref

Focus stack from 19 images. Automated capture using Helicon Remote and post-processed with Helicon Focus.

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Moving to Medium Format?

I wouldn’t comment on product announcement unless the product is exceptionally interesting, or as the teaser said, a game changer. However, those words have been (ab)used before, in particular in the mirrorless* world, and have eventually left something to be desired.

For everyone who missed it: Hasselblad have announced a 50 MP medium format** (44×33 mm) mirrorless camera with a 2.36 MP electronic viewfinder (EVF). There also will be a new lens line with leaf shutters, for a large range of shutter speeds (60 minutes to 1/2000 seconds) and with full flash synchronization to boot. Rumors had it for Sony and Fuji for a while and I would not be surprised to see a similar offering by Pentax; possibly at Photokina in September (my flight is booked).

Linhof

A DSLR (Nikon D810) as a digital back on the Linhof Technika. A medium-format mirrorless camera would make a better combo because of the shorter flange-focal distance and the larger sensor.

*They really should come up with a new name for those cameras, on the same footing that we are not driving horseless coaches.

**Well, not quite to medium-format film standards ranging from 60×45 to 60×90 and even 60×170 panoramic.

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Posted in Equipment reviews, Image quality, Philosophy+Opinion Also tagged , , |

Testing Lens Alignment

A year without new gear hasn’t been really successful. And although we have seen a lot of new equipment this year, there was nothing to merit a complete system change (to the Sony mirrorless or the Pentax 645, for example).

align1

My target for testing lens alignment. Almost a nice image in the autumn fog.

After the disappointing test of the Nikon 24-70 f/2.8 VR, I thus treated myself to a Zeiss Distagon T* 25 mm f/2.0. Great deals can be had on these “classic line” Zeiss lenses, because they will be replaced by the Milvus lenses. The Milvus 50 f/1.4 and 85 f/1.4 are new designs, while the others are basically avatars in an Otus gestalt.

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Four Ways to 85 mm: Three Nikon Lenses and the Carl Zeiss Planar for the Hasselblad V-Series

Fighting hard against GAS (Gear Acquisition Syndrome), I still have four ways to arrive at 85 mm focal length. I may therefore check out some widespread myths about lenses: 1) Prime lenses are better than zooms. 2) Vintage lenses are ill suited for digital sensors because they are not telecentric, that is, the ray angles at the edges of the sensor exceed the acceptance angle of the microlenses, which results in reduction of color saturation, and color fringes. 3) The 35 mm lenses have a better resolution than medium and large-format lenses, simply because they need to cover only a smaller caputure area and can therefore be made from more expensive glass.

Lenses

From left to right: Nikon AF-S 70-200 f/2.8 G ED VR II, Nikon AF-S 85 f/1.8 G, Nikon PC-E 85 f/2.8 Micro, Hasselblad Zeiss CF 80 f/2.8 Planar T* mounted on a Photodiox adapter.

The contestants

  • Nikon AF-S 70-200 f/2.8 G ED VR II
  • Nikon AF-S 85 f/1.8 G
  • Nikon PC-E 85 f/2.8 Micro
  • Hasselblad Zeiss CF 80 f/2.8 Planar T* mounted on a Photodiox adapter

I hated the Nikon AFS 70-200 f/2.8 and the Canon equivalent, because having set up my large format camera, I was more than once harassed by photographers carrying these lenses. Considering their form factor it does not need much to imagine what some guys are compensating for.

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