The Tiffen 6 x 4" Decamired Blue 1.5 Cooling Glass Filter - For those who want a sure-fire way of getting accurate color temperature readings, the decamired system is the way to go. Using this formula, you can transpose temperatures from one point to another easily and quickly. This system is also useful when you wish to bring a certain amount of creativity to color photography.

Applications include keeping color temperature constant during the course of the day and producing the effect of different times of day. Available in two series, reddish filters that warm the light and bluish filters that cool the light. Each series contains 4 densities: 1.5, 3, 6, and 12. Filters in the same series can be combined.

Decamired filters are designed to more easily handle unusual color temperature variations than the previously mentioned filters. Available in increments of both a red and a blue series, Decamired filters can be readily combined to create almost any required correction. In measuring the color temperature of the light source, and comparing it to that for which the film was designed, we can predict the required filtration fairly well.

A filter that produces a color temperature change of 100K at 3400K will produce a change of 1000K at 10,000K. This is because the filter relates to a visual scale of color. It will always produce the same visible difference. A color change of 100K at the higher temperature would hardly be noticed.

Calculations
To use this concept, subtract the mired value of the light source from that of the film. If the answer is positive, you need a reddish filter; if negative, use a bluish filter. Mired-coordinated filters are termed as decamireds. Mired value divided by ten yields decamireds. The 60 mired shifts, above, would be produced by an R6 filter, where the higher values were that of the lighting.

Sets of such filters generally come in values of 1.5, 3, 6, and 12 decamireds in both B (bluish) and R (reddish) colors. These numbers are additive; that is, a pair of R3's produces an R6. An R6 plus a B6 cancel each other out to produce a neutral gray.

Used for Temperature Control    Available in Specific Increments    Warming and Cooling Variety

The decamired system has an advantage over the Kelvin system in that the Kelvin scale is not linear

Decamired readings provide more accurate/controllable readings than Kelvin

The difference between the Mired value of the film and the Mired value of the light is the Mired value of the correction filter that correctly tailors the light to the film

Related Questions and Answers

Q: 1. I think this lens would block partially the viewfinder on a Leica M3. Does anybody know how much?

A: Very slight block, not enough to be a hindrance.

Q: 2. Hey guys, is this full frame ? Thanks.

A: Yes

Q: 3. What is the process like for getting it calibrated for focus wide open?

A: The ZEISS C-Sonnar always comes with an adjustment of its flange focal distance (FFD) with the best compromise regarding its focus shift at all f-stops and taking distances. For most applications, this is the perfect adjustment for 95% of our users. If you intend to use the C-Sonnar only at f/1.5 and closer working distances, a different adjustment of its FFD could be considered. We recommend running some practical tests with your M-mount camera body before considering an individual adjustment of your lens. If you determine an adjustment of the focus is necessary at f/1.5, then the lens can be sent to ZEISS for adjustment (go to: a href= http://www.zeiss.com/camera-lenses/en_de/service/repair_service.html#zm-mount---zi-camera target= _blank http://www.zeiss.com/camera-lenses/en_de/service/repair_service.html#zm-mount---zi-camera/a to start the process) . If the lens is under warranty, this work is completed at no charge. If the lens is out of warranty, then a service charge is applicable.

Q: 4. Weather sealing for light rain or dust?

A: Unfortunately, the ZEISS C Sonnar T* 50mm f/1.5 ZM Lens (Silver) is not weather sealed for light rain or dust.

Q: 5. Can the aperture ring be declicked for smooth iris control?

A: No it cannot.

Q: 6. will this work with new Leica M6?

A: Yes. The Voigtlander Nokton 75mm f/1.5 Aspherical Lens is compatible with the Leica M6.

Q: 7. Can B&H arrange for the recalibration of the focus to wide open at 1.5?

A: Not that I know of. You need to contact Zeiss directly.

Q: 8. Will this fit an M4P?

A: Yes, this is an M-mount lens so it will fit a Leica M4P.

Q: 9. Initially, when the c-Sonnars were first issued about 10 or so years ago, I beleive Zeiss calibrated the optimal focus to 2.8. Later they could be ordered optimized at f/1.5. In the past few years I've read optimum focus is set at f/2. What is the optimum focus on this particular production series? Thanks.

A: The ZEISS C Sonnar 1.5/50 ZM is currently optimized for focus at f/2.0.

Q: 10. What adapter should i use to adapt to the sl2?

A: The best adapter is the Leica adapter: https://www.bhphotovideo.com/c/product/1046772-REG/leica_18771_m_adapter_t_for_leica_t.html