Avoiding star trails - the 600 rule

Star trails are nice, but maybe you evaluate it can be too much distracting for a certain night shot and opt to avoid it. It has an inherent eye catching property that makes it almost impossible to not be noted, before any other photographic composition element.
That's where the "600" rule can help you, to better control the displacement of the stars lights over the surface of the film or digital sensor. This rule says:

600/FL*CF=ExpT

Where FL is the Focal Lenght, CF is the crop factor of the film or digital sensor and ExpT is the exposure time in seconds.

Let's say you place your tripod over a beautiful night scene, with this gear:

Camera: Canon with APS-C size digital sensor - 1.5x crop factor
Lens: 24mm

FL = 24 * 1.5 or FL = 36
600/36=ExpT or 600/36=16.6s

With this lens and sensor size, you'll need 16.6s of exposure until the star trails begin to show in the image. But 15 or 16 seconds will also be very good for this purpose. If, for night shots, you have a manual exposure meter as I do - I had acquired 3 Gossen Lunasix in the past years for very few money as people prefer in this days go digital with built-in meters - all you have to do is to adjust your exposure index (ISO), exposure time in seconds - as the "600" formula above - corresponding f-stop and shoot.
If you're doing the photo with film, don't forget to compensate the exposure indicated by the meter with the reciprocity factor made public by the film manufacturer for each film variant.

So, for the gear configuration shown in this article, if you intend to have star trails on the picture, 16s is the beginning of the exposure time, and if you prefer to avoid, you have 16s to play with your gear settings until the trails beggin to appear. 

In both cases, have fun!

Rollei & Zeiss lenses - differences and similarities

The T* coating of Zeiss lenses was developed by Zeiss. The HFT (High Fidelity Transfer) lens coating was developed by Rollei from Braunschweig with Zeiss in the '60s. Some years later - about the first years of 1970 decade - Rollei had licensed from Zeiss the production of a lens series for the SL35 Rollei 35mm reflex cameras. The production took place at the Voigtlaender factory in Braunschweig - Germany.
The HFT coating have a color more toward the Red, and the T* coating toward Purple and Green. By my experience with Zeiss lenses and Rollei QBM HFT, with T* coating I can expect more contrasted images and with HFT less contrast, under the same tonality range, from shadows to highlights.

Is there any difference between one or other coating for the same lens focal concerning the results? It depends of the available lightning, the subject, the average scene contrast, to name few. If you have the chance to have both coatings, do it. If you don't, choose the coating which will work better with the type of subject and light you use to photograph more often.

The coating choice have to consider also which post-processing techniques and media intended to use - screen, digital or wet printing. If you shoot also analog, as I do, what's available to you as paper grade, and enlarger type - condenser of diffused light type.

For the type of work I do, mainly landscape and portrait, I find the Zeiss T* coating the better choice for landscape and nature, and I have some shots made on street style photo, for which I prefer the same lens coating. On the other hand, the subtle differentiation between tone rendering pleases me more at portraiture when I choose a HFT coated lens. It seems to be more controllable, demanding less post processing work.

Rua/Street, Sao Pedro do Sul - RS - Brasil
Contax 167MT + Zeiss Planar 1.4/50mm, Kodak Tri-X 400 135mm, HC-100 dil F

Denise - Rollei QBM Planar 1.8/50mm

Lens design, lens names.

Usually a lens project or original optical design deserves a particular name: the name is given for the lens elements number, placement, size and position. We find that on lens names like Petzval , Dyalit, Tessar, Gauss and Double Gauss, etc. Sometimes the original project lens name continues even if the original lens project is enhanced at later time, as in the Heliar original project from Voightlaender which had come the Apo-Lanthar many years later, but we can trace the DNA of the Heliar design on it. This is not the case with the lens manufactured by Leitz Camera (Leica): their lens names designates the max aperture or speed of the lens itself, rather then the optical scheme.

• Elmar = f/4 or slower
• Elmarit = f/2.8
• Summitar = f/2
• Summarit = f/2.5
• Summicron = f/2
• Summilux = f/1.4
• Noctilux =f/1.2 or faster

Other names like Summar seem to vary more.

image from: en.leica-camera.com/Photography/Leica-M/M-Lenses

Lets begin the damn thing...

There is a wolf singing in the forest, but the hunter who's passing next to it is deaf.