Joshua Cadmium

Yep! A lot of Red shooters found that out on the earlier sensors that were noisy in Tungsten light. Digital sensors are natively 5000K so getting the temperature as close as possible to that will maximize dynamic range and SNR. That is because the red channel will clip first in 3200K Tungsten light, but all channels will basically clip equally at 5000K. So, you can gel or dichroic filter Tungsten to 5000K or use a filter on the lens to get to 5000K. If you do that, though, you do need to increase the light hitting the sensor, otherwise you would just be increasing noise. (If you are right below clipping on the Red channel and filter the light, it's just going to increase noise across the board since a lot of light is now not making it to the sensor. However, even if you don't increase the amount of light, I strongly suspect you may still increase color fidelity at the expense of noise, depending on the neutrality of the blue filter and how well the blue filter and the sensor cuts infrared pollution.) Going way further, blue light is actually physically smaller than red light. When we describe light as a certain nanometer, it is literally the length of the wavelength of light. Blue light starts around 450nm and Red around 625nm. By shifting more light to a higher Kelvin temperature, you are actually shrinking the overall size of the light. This actually increases the effective resolution you can capture. This won't be apparent on most sensors (unless way stopped down at or past diffraction) but it can play a role on smaller pixel sensors, such as on the Blackmagic 12K with its 2.2um pixels, since diffraction on smaller pixels starts at a larger f-stop. And this effect may be more apparent on future sensor designs with even smaller pixels, especially when cropping in.

Some zooms may cover with a 1.4x extender. Tokina makes a 1.6x extender. IB/E Optics has a 1.66x expander as well.

I'd still check with them about the screws - I don't know if you can reuse the ones on the bayonet mount.

The person that used the P+S Technik one used it on a standard speed that was Arri bayonet. I don't know for sure about the VP one, but I'm almost positive it's for vintage lenses. You could always email the companies and ask them.

P+S Technik has them: https://www.pstechnik.de/pl-adapter-arri-vorm/a-1012/ . I heard from someone that bought them that the screws they sent were not a direct match and they had to source their own. Visual Products also sells them: http://www.visualproducts.com/storeProductDetail02.asp?productID=1111&Cat=3&Cat2=43

Oh, I wasn't trying to imply that a bulb of a certain wattage always has a particular thickness, just that higher wattage filaments are thicker than lower wattage filaments all other things held constant. Thicker wires will produce higher wattages, but you have to hold the other part constant, the length of the wire, which is voltage. I don't know how accurate it is in terms of Ohm's law, but in my mind I picture a certain length of wire that produces a certain wattage. I can stretch out that wire to make it thinner (more volts) or I can squash it together to make it thicker (less volts), but the wattage stays the same. The main point, though, is that lower voltage bulbs of the same wattage would be more robust - smaller in length and thicker - which I think you agree with as well. (And thicker and shorter filaments survive higher temperatures better, which leads to increased lumens at the same wattage.)

This document from Osram is my favorite in terms of explaining how tungsten bulbs work: https://www.bulbconnection.com/file_assoc/63_FL_114103.pdf It states on page 9 that: "The wire length is mainly determined by the lamp operating voltage. The higher this is, the longer the piece of wire the lamp bulb must contain. The wire in a 24 volt lamp is between 10 and 14 cm long, the wire in a 12 volt lamp is only half that length. The wire diameter is mainly determined by the required lamp wattage and life. The higher the wattage, the thicker the wire, and hence also the stronger it is mechanically." That seems quite clear cut. I don't know why it is what it is in terms of Ohm's law, just that it is what's described here. I'd love to see the math behind it all, though. -------- Keeping wattage constant, a bulb that operates at a higher kelvin temperature will definitely produce more lumens than a bulb operating at a lower kelvin temperature. But, higher kelvin temperatures will definitely reduce bulb life. Plug in any given bulb here: https://www.ushio.com/support/halogen-lamp-life-estimator/ . You can see the impact temperature will have on lamp life and lumens. With classic Dedolights, for instance, one of the reasons the bulbs last so long is because they were designed to operate at 3400K but can operate at 3200K with a drastically increased lifespan. As well, the filament is more robust and will survive mechanical failure from fixture movement much better than line voltage bulbs.

If by current, you mean amperage, I'm almost positive you are correct in assuming that at a certain wattage, you have to increase voltage in order for the amperage not to be too high. However, the main issue with tungsten efficiency is filament temperature and life. A burning tungsten filament sloughs off atomized tungsten that either blackens the bulb (regular incandescent) or is redeposited on the filament due to the halogen cycle in tungsten halogen bulbs (but it is not always redeposited where you want, so parts of the filament still get thinner.) The failure point of a bulb is normally when the filament gets a weak point that breaks - and it increasingly does so at higher temperatures. While wattage is related to the thickness of the filament, I have read that lower voltage filaments are in general thicker than their higher voltage counterparts (but I have not been able to confirm that). I haven't fully explored the math behind everything, because it gets complicated, but I'm fairly confident that the main reason that lower voltage bulbs are more efficient is that they can be pushed to a higher temperature without the filament breaking down too fast, either because it is thicker, or, since the length is shorter, there is less surface area for weak points to develop. Manufactures test their bulbs by how many fail in a certain timeframe and at some point, the economics make it so that bulbs need to last for a reasonable amount of time. Most of the high efficiency bulbs I've seen burn at 3400K and last for 50 hours. -------- Compactness does help with optics, but voltage definitely plays a role in the amount of lumens that can get to those optics, and it is actually apparent in Source Four HPL bulbs. As the voltage goes up, the lumens go down, but the hours stay the same. This is from ETC's data: 750w 240v 300 hour HPL = 19,750 lumens at 3200K / 26.3 l/pw 750w 120v 300 hour HPL = 21,900 lumens at 3250K / 29.2 l/pw 750w 77v 300 hour HPL = 22,950 lumens at 3250K / 30.6 l/pw So, a 750 watt 77 volt HPL is about 16% more efficient than a 240 volt HPL. -------- I have actually been looking at this for awhile because I was trying to determine the highest amount of tungsten light I could run on house power. There is no 50 hour HPL bulb - 300 hours is the shortest anyone makes. (I'm pretty sure it's because no theater is going to want to change bulbs that often.) So, I started looking at overvolting with a variac, which increases the temperature of tungsten, and thus the efficiency. The 77 volt bulbs (which are normally used on ETC's dimmers) are already more efficient, but they might take overvolting better if the filament is more robust than mains power bulbs. If I ran a 77 volt HPL at about 88 volts, it would hit that 50 hour criteria, which should also get me to about 37 lumens per watt. With a 550w 77v bulb, I'd be hitting about 25560 lumens at 680 watts. (Overvolting 750w bulbs might generate way too much heat to be safe). Also, you shouldn't run two 750w bulbs on 15 amp mains power (1440 watts is the 120v 15a continuous limit) so this would help me get close to that limit without going over. It would end up being 17% more efficient than a 750w 120v bulb, but at a lower wattage (or 28% more efficient total). On top of that, the efficiencies from overvolting increases when you consider that sensors want to be at 5000K. So, getting closer to that temperature is either going to make the image look better (less saturated red channel) or make it so you lose less light when converting tungsten into 5000K by using gels or dichroics. The difference between 3250K and 3450K is 1/8 CTB, which would be a 25% light loss for gels and a 12.5% light loss on dichroics. Now, I don't know how safe overvolting might be on Source Fours. At 88 volts that bulb is going to be around 3500K, which should be okay. There is brief inrush for tungsten, which can take it past the melting point, but you can mitigate that by gently bringing up the voltage from 0. When I talked about overvolting in general with ETC, they said I just risked catastrophic bulb failure (glass shattering). I'm going to be experimenting with this soon, though. Again, probably more info than you wanted, but perhaps helpful.

Here's a longer explanation than this needs: With all incandescent lights, which include quartz halogen, the filament is just a resistor that turns electricity into heat. So, you'd want something that burns the hottest before it melts. Of all the elemental metals, tungsten has the highest melting point at about 3700K. (In fact we can't practically make a container to hold molten tungsten, so anything made out of tungsten is sintered together). Since a filament is just a resistor, the shape of that filament determines how much electricity it gobbles up. Wattage is mainly determined by thickness and voltage is mainly determined by length. As thickness increases, so does wattage and as length increases, so does voltage. So, a low voltage bulb has a filament that is smaller in length than a higher voltage bulb. A filament is not just a straight line, though, but a coiled coil, so a low voltage filament bundle is also more compact. Compact filaments structures help in two main ways. One is that because the area of the filament structure is smaller, you can design optics and reflectors that are more precise. You see this precision in Dedolights and MR-16 bulbs. The other, is that smaller filaments do not need as much electricity to keep them hot (according to this site: https://www.lrc.rpi.edu/programs/nlpip/lightinganswers/mr16/performance.asp ). With tungsten, the hotter it gets, the more efficient it gets. Technically, tungsten is almost perfectly efficient - it converts electricity to radiation at an almost perfect 1 to 1 ratio. Unfortunately, most of that radiation is outside of visible light - it's in the infrared spectrum. The hotter you heat tungsten, though, the more that radiation shifts to visible light (otherwise known as lumens). At 2100K, it's about 4 lumens per watt. 2500K is about 9 lm/w. 3000K is about 21 lm/w. 3200K is about 27 lm/w. 3400K is about 33 lm/w. The limit before Tungsten melts is about 37 lm/w. So, the short answer is that lower voltage bulbs are more efficient because they have smaller filaments that more easily burn hotter, which provide more visible light per watt. But wasn't the long answer more fun?

I just double checked and Formatt is having a 50% sale on all of their Firecrest filters, including clearance ones, until Monday: https://formatt-hitechusa.com/collections/clearance 4x5.65 is $180 and 138mm is $99. The older filters are exactly the same as the newer ones according to this: https://cdn.shopify.com/s/files/1/0267/9934/1677/files/Formatt_Firecrest_Ultra_Brochure_-_Updated.pdf

So, if you can deal with the lack of coverage, you might be okay, but 4x5.65 is the standard for everything besides rotating filters. The market for 138mm NDs is small, so resale will take a hit if you ever decide to step up to 4x5.65. I know Formatt has their 138mm Firecrests on sale for $200, but they've been on sale for a while and no one is buying, if that tells you anything.

Another important point is that 138mm round filters will have less coverage than 4x5.65 filters. Since we are always dealing with rectangular aspect ratios, a 138mm filter in the same 1.4125 aspect ratio of a 4x5.65 filter will cover about a 79.7mm x 112.6mm rectangle A 4x5.65 filter covers a rectangle of 101.6mm x 141.5mm So, 4x5.65 filters offer about 25% more coverage in both directions. But that's at a 1.4125 aspect ratio. As you go wider, the 138mm filter can make up some ground, but it still does not cover as well as a 4x5.65 does. At a 1.85 aspect ratio, a 4x5.65 covers a rectangle of 76.5mm x 141.5mm. A 138mm would cover 65.6mm x 121.4mm. That's about a 15% difference in coverage in each direction. At a 2.39 aspect ratio, a 4x5.65 covers a rectangle of 59.2mm x 141.5mm. A 138mm would cover 53.3mm x 127.3mm. That's about a 10% difference.

I have two of them that I picked up used, so I don't know exactly when they were made. They definitely came from different batches as the engraved font on the aluminum is different, but they were quite similar - about 7 mireds different between the two of them. They do seem to be on the green side by eye and as measured by my lower end Illuminati color meter (they were reading around +1/2 green). They are definitely correcting to daylight kelvin values, though. However, I was not testing them with DLH4s - I was testing them out with Dedocools, which (at least on the one's I own) don't have room for a front filter - the front glass element sticks too far out. I found that I could jam the filter in at an angle and use a cable to keep it from falling out. Partially because of that, I realized that the filter is less green and appears neutral (+0 green) depending on the angle I have it at (while still correcting to daylight.) Dichroic filters work by passing part of the spectrum you want and reflecting less (or none) of what you don't want. They are impacted by the angle of the light as it travels through them, so that's why tilting the filter impacted the color I was getting. So, YMMV on a DLH4, but I hope this might help a little. Also, Dedocools are about as loud as a blowdryer, if anyone was thinking about checking them out. ?

Here's a fantastic example of using the Parallel Beam Attachments with DLH4s and the Lightstream Reflectors: In the example, he's only using 4x 150w Dedolights, so only 600w total. Pretty efficient.

Tungsten in general is still the king when it comes to color rendition - it's the only light source besides the sun and fire that gives perfect color. It's 100 CRI, TLCI, CQS, etc. With tungsten Dedolights, you have numerous benefits over regular tungsten lights. Most Dedolights (including the DLH4) use low voltage bulbs that are more efficient than higher voltage bulbs because the filament itself is more compact and doesn't need as much electricity to keep it hot. Because of that, whereas most tungsten units are about 15-20 lumens per watt, Dedolights get up to 35-40 lumens per watt. Dedolights also use aspherical optics that capture all that light and condense it into an even beam. Standard fresnel lenses can be very inefficient, especially when spotted down. Also, Dedolight does has dichroic daylight conversion filters for their tungsten lights, including the DLH4. So, while gelling the light will indeed cut two stops, the dichroic filter will only cut one stop. The bulbs should also not be going away anytime soon. Halogen bulbs are typically still on the market because they are more efficient than non-halogen tungsten. These low voltage bulbs are about double the efficiency of high voltage halogen. Since you were planning on using the Light stream reflectors, Dedolight does have the Parallel Beam Attachment that increases the amount of light when in full spot by 400% (since you use it in the flood position, which gives out the most quantity of light.) Also, while most tungsten units are cheap on the secondary market, I find it telling that Dedolights still hold their value.

Thank you so much for the info! I was actually hoping to hear from you specifically, so that was super helpful.

Anyone want to chime in one way or the other and offer some opinions? ? Basically, would 1-3 lbs of unsupported weight damage the focusing threads if no focusing was actually being done?

I have a Century Double Asphere and a bunch of other heavy wide angle adapters I want to use with a Zeiss 10-100 T1.8 MK II and a 12mm T1.3 MK II. I know that due to the telescoping nature of the helical focusing threads, you shouldn't have anything heavy (or at all) attached to the front of the lens while focusing, like a clip on matte box. I was wondering, though, if the threads would be okay if I prefocused the lens, then attached a wide angle adapter, and then did not focus the lens at all while the adapter was clamped on. (I know I would need to find the exact focus point for non-zoom through adapters, like the Double Asphere, but I'm not worried about that.) With the 10-100, it also has the macro mode, where the focus wouldn't be extended at all and be at its starting point on the threads. I'm also thinking about using an anamorphic adapter, plus a front variable diopter, which would be several pounds hanging off the front. If I went that route, I would have each part individually supported on rods and, again, would not touch the focus at all at that point, but I don't know how safe that would be. Those two lenses currently have perfect focusing, especially for their time and I really don't want to wreck the threads.