Thursday, June 28, 2012

View from Puijo tower

Below is 360 degree panorama from the observation deck of Puijo tower in Kuopio. The tower itself is 75 meters in height and resides on a 225 meter tall hill.

The panorama is over six hundred megapixels in size, one can zoom in quite deep into the image.


OpenZoom, press F for full screen mode or use the controls in image.

The observation deck looks like this:


Puijon tornin näköalatasanne in Kuopio

This post was originally posted on Pallopanoraamablogi on 2012-05-18 as "Puijolla".

Wednesday, June 27, 2012

Flat field box for fisheye

Flat field images are used in astrophotography to rid images of vignetting, dust on sensor plane and to even the general unevenness of light field. Shooting flat field images for longer lenses is relatively easy, one only needs an evenly illuminated featureless object. However, with fisheye lenses and their immense field of view and depth of field, there are certain problems one must solve.

Because the field of view is usually about 180 degrees from corner to in case if diagonal fisheyes and the same 180 degrees from edge of the imaging circle in case of circular fisheyes, one cannot just point the lens to something white and featureless and expect a good result. The lens needs to be quite close to the surface and the surface must be curved or round to cover the whole field of view.

The surface also must be non-reflecting. This can be achieved using white acrylic glass which is then sanded with very fine grit, around one thousand in CAMI grit designation. Coarse sandpaper should not be used to avoid visible streaks.

Unusable flat field image from fisheye
(Stuff gets reflected into the flat field image.)

Another problem is that the camera and lens casts a shadow on the acrylic glass. One must block the light entering behind the camera, black cloth or black painted flat field box can be used to counter the extra light.

Here's one version of a flat field box for fisheye lenses:


1: inner walls should be painted black, 2: curved acrylic glass sanded matte 3: diffuse light source, be it a window or similar. Top and bottom should also be covered.

For circular fisheyes the acrylic glass should be curved in two dimensions, not just one to cover the field of view. Hot air blower can be used to help making the curvature. Paper should not be used in place of the plexiglass as it is not homogenous enough.

Below is an example of the effect of flat field correction on spherical panorama embedded with Saladoplayer.



Look straight down for the most visible effect. Here's single image, with flat field correction enabled and without:

Kalansilmäobjektiivin värivääristymien korjaus Raw Therapeen flat field correction -työkalulla

Flat field correction was done in Raw Therapee. It detects the lens used and loads the corresponding flat field image automatically. If there are multiple falt field images, the images are either stacked or the best one is selected using various criteria.

This article is adapted from post on Pallopanoraamablogi titled "flättiboksi kalansilmälle" and "flättiruutujen vaikutus pallopanoraamoihin".

Tuesday, June 26, 2012

Sirui K-20X ball head in review

I've been shooting for years with my Chinese-made unbranded KS-0 ball head that I bought from Dealextreme.com. While it is quite sturdy ball head, it has some quirks, which've led me to look for a better alternative. The alternative which I've now bought is Sirui K-20X which I'll now review.

Sirui is also made in China, but it tries to separate itself from the numerous white box manufacturers as a premium brand. Sirui's K-20X ballhead was purchased from Poland, Foto-tip.pl's online store to be exact. Amazon also sells the same head for about the same price.

Below are the main specifications of both ball heads:

KS-0 Sirui K-20X
KS-0 Sirui K-20X
Approximately 31€ at time of purchase, now a tad more (Dealextreme.com) approx. 100€ (foto-tip.pl)
The tightening mechanism of the ball is with two screws. Panning has also its own screw. Screw handles have rubber coats. The tightening mechanism of the ball is made with one screw with a limiter. Panning has its own screw. Screw handles have rubber coats.
Arca-Swiss compatible quick release plate with anti-slip rubbers. Can be attached to tripod with either 1/4" or 3/8" screw, adapter supplied. Arca-Swiss compatible quick release plate with anti-slip rubbers and anti-twist feet. Can be attached to tripod with either 1/4" or 3/8" screw, adapter not supplied.
approx. 475 g approx. 400 g

Build and construction

Whereas KS-0 was delivered in white, partially crushed cardboard box without any documentation whatsoever; had the Sirui's ball head instruction written in good English, nice neoprene pouch and Allen key. Even though the pouch probably won't be used and the instructions for simple accessory aren't really needed, it gives warm and fuzzy feeling in the customer.

Both ball heads have Arca-Swiss compatible quick release plates. Sirui's supplied TY-60 quick release plate is tad larger (60mm x 48mm) than KS-0's plate (40mm x 50mm) and features anti-twist feet for attaching heavier cameras. Sirui's quick release plate's screw also has hexagonal socket to tighten the screw further than is possible using bare hands. KS-0's quick release plate's screw has a slot that can be tightened using a coin or similar, it has no handle unlike the Sirui's screw, which is a nice detail.

Thursday, June 21, 2012

Our galaxy and sky in infrared light

NASA released some time ago full sky image taken by WISE (Wide-field Infrared Survey). Unluckily NASA only released the image as a flat, zoomable image instead of spherical panorama which it is so I'm releasing one.

Below is embedded spherical panorama with SaladoPlayer of the sky in infrared light. In the middle is our galaxy - The Milky Way - as a bright stripe of stars since we are observing it from the inside accompanied by the surrounding skies.


Image credit (IR): NASA/JPL-Caltech/WISE Team, image credit (visible): PhotoPic Sky Survey, cc-by-nc

From the drop-down menu one can change between visible light sky as captured by Photopic Sky Survey and the infrared sky. I've also added some informational hot spots to the image to help navigating oneself in the image. The panorama can also be seen in 360cities.

This post originally appeared on Pallopanoraamablogi as "Infrapunanäkymä galaksiimme" at 2012-03-17.

Kuopio's marketplace in a gigapixel panorama

Below is 2.7 gigapixel panorama of the Kuopio's market square renovation. You can zoom into the image and drag it around.


(One can change the panorama on the fly from the drop-down menu.)

Technical notes: middle portion of the image is shot with the venerable 105mm f2.8 VR Micro-Nikkor. Four rows of images were shot and stitched together in Hugin. Additionally, two rows of images were shot with Tokina 11-16mm f2.8 lens at 1mm setting and stitched together. These two panoramas were then combined to offer both resolution and good coverage over the scene.

Because handling and processing of images that are in the size of several gigabytes or -pixels is quite challenging, the panorama was stitched straight into cube faces with Hugin and Multiblend. Surprisingly, this worked quite well as no seams between the cube faces can be seen.

However, the tiling of the image for displaying didn't go so smoothly as SaladoConverter kept crashing. So, the tiling had to be done with Zoomify's ZoomifyConverter and the tiles renamed to conform to file and folder structure SaladoPlayer uses. Since Zoomify doesn't use any overlap between tiles, some seams can be seen when zooming is set to minimum.

This post originally appeared on Pallopanoraamablogi as "Kuopion torityömaa gigapikselipanoraamassa" at 2012-05-19

Adobe Lens Correction Profiles compared

Adobe Lens Profile Downloader profile info window Version 4.0.9 was released of the raw photo process raw Therapee, which has the ability to use Adobe's Lens Correction Profiles (LCPs). LCPs can correct light falloff (vignetting), lens geometry (distortion) and chromatic aberration. Raw Therapee itself doesn't have any correction profiles built-in, but one can acquire most of the by installing Adobe's Camera Raw with Photoshop or DNG Converter. Not all lenses have correction profiles, for example the Tokina 11-16mm f2.8 lens wasn't included so it had to be downloaded separately using the Lens Profile downloader, a small AIR applet. Funnily though, Samyang's 8mm fisheye lens didn't have a correction profile at all.

Care must be taken when downloading the profiles. Most user-supplied profiles only have vignetting correction measured for only one small aperture. For example profile that has light falloff correction only for aperture f/11 can't be used to remove vignetting at larger apertures. It's a good idea to take a look at the calibrated apertures and focal length before applying or downloading the profile, see the screen capture on the right-hand side of the page for example of a quite thorough profile.

Below is a mouseover image with a lackluster profile that has the light falloff correction only for aperture f/11. Even though there seems to be some extrapolation of vignetting correction values, it is just not enough to rid of all of the vignetting.


Move mouse over the image to see the LCP corrected image, flat field corrected image acts as a reference. Image taken with the Tokina 11-16mm f2.8 lens with wide open aperture and at the lenses widest setting.

Below is another example image pair with a better profile, that corrects most of the vignetting. Do note however, that the corner color shift can't be corrected, hence the greenish cast in the extreme corners.


Move mouse over the image to see the LCP corrected image, flat field corrected image acts as a reference.

For example, there's user submitted profile for the old Nikon 50mm f1.8D AF lens that's been calibrated twice for each aperture at different focusing distances. Focusing distance can affect the vignetting and most probably the distortion of the image. However even that profile can't correct for the hot spot problem the lens has; at smaller apertures (f/5.6 and onwards) a round, brighter area appears in the center of the image. It's cause by the aperture blades reflecting light back from the sensor.

Below is a mouseover image pair, flat field corrected photo is used as a reference.


Move mouse over the image to see the LCP corrected image, flat field corrected image acts as a reference.

Both Sigma and Tamron offer 'official' profiles straight from the manufacturer, Nikon and Canon seem to want to keep the users on their own respective pieces of software.

This post originally appeared on Pallopanoraamablogi as "Adoben korjausprofiilit" at 2012-05-12

Welcome

Tukkimiehentäi (hylobius abietis)Welcome to Equirectangular, the blog with and about photography, panoramic photography, spherical panoramas and virtual tours.

This blog will (hopefully) be the English language off-shoot of Pallopanoraamablogi, which I've been writing since spring 2010. Most posts shall be translated from the master blog, but we'll see if there's any exclusive content to be posted here.

Siilinjärvi's Tarinaharju forest path virtual tour

Tarinaharju virtual tour thumbnailsSiilinjärvi's esker area known as Tarina has some very popular pathways. Housing an old TB hospital, the area was known for its fresh air in the beginning of the 20th century.

Below is embedded a sixteen image long virtual walk, the green arrow takes you deeper into the forest and the dark orange/red moves you backwards in the tour. A thumbnail list of the images can be seen when clicking the middle button (compass) in the bottom-right corner of the player. All the beautiful places of Tarina without the annoying mosquitoes.



This post originally appeared in Pallopanoraamablogi at 2012-06-08, titled "Virtuaalinen metsäreissu Tarinaharjulla"