sal_santamaura

Those are the best, but apparently have been discontinued. I stockpiled a handful before they mostly disappeared (just a few out there now) from retail distribution. When they're gone, the only silver oxide alternative I've found is these: https://www.bhphotovideo.com/c/product/1062384-REG/exell_battery_s28px_6v_silver_oxide.html Excell seems to make them in batches, so they're often out of stock until another shipment comes in.

Silver is optimum and lithium is OK, as long as one pays attention to the lithium's voltage and replaces it after it's gone through about half its service life. See all the gory details in this thread: https://www.photo.net/forums/topic/28385-pentax-digital-spot-meter-battery-question/

In answer to your question: the distance depends on a number of factors, especially diameter of reverse-curl feed rollers. I won't relitigate this matter, with so many dismissing it out of hand despite evidence. Rather, I refer you to a 22 year old thread in which my posts covered everything in detail:

q.g., tangential pontificating, misguided at best, in a thread about batteries for the Pentax digital spot meter reminds me of the "argumentation for argumentation's sake" I remember on photo.net a couple of decades ago. Might that be why this has long not been a dominant source of large format photography information? Spot meters are ideal tools when used with large format cameras for determining both optimum exposure settings and optimum film development. Such is the raison d'etre of spot meters. Incident light meters are useless for that purpose. Yet again, this completely misapprehends the entire concept of development alterations. Based on spot meter readings / subject brightness range, negatives are tailored to each specific scene. Film/development doesn't care about incident light. Film/development responds only to light falling on the film. Selection of a specific developer, development regime and development time for individual sheets of large format film requires knowledge of the latter. Development determines how much contrast the film can handle. Knowing the former can, in fact, only succeed when a scene of compatible reflectivity is accidentally photographed by a film/development combination that matches it. If subject brightness range exceeds compatibility, it will fail. If subject brightness range is substantially lower, one might be able to use higher paper contrast (although the days of grade 6 paper are long gone), but results will be less than optimum. I will not further engage in this tangent and distract from the thread's purpose. If you are compelled to get the last distracting word, I'll not respond. Future readers ought understand that the Pentax digital spot meter is an ideal tool for large format film photographers. Its battery requirements, when understood, enable users to obtain consistent readings of reflected light, then use those readings in a straightforward way (after testing their materials) to make optimally printable negatives.

That repeats the oversight of your previous post. A spot meter doesn't "bias" any readings. It provides essential information about the subject reflectivity / brightness range that is used not to measure light falling on a scene, but light hitting the film. That, in turn, informs not only the exposure, but the development given to each individual sheet of large format film. There's no "guesswork" involved. Intentional placement, followed by expansion, contraction or "normal" development (all established by prior testing), optimize negative contrast index to match paper. Incident metering can succeed only if the subject brightness range happens to match an "average" film development's contrast. Unless using multiple roll film backs with medium format cameras, or multiple bodies with 35mm cameras (each back/body assigned a different development time), that limitation of incident metering is something one must put up with. Otherwise, using a spot meter eliminates guesswork about whether a scene can be recorded on film in a way compatible with printing paper's range.

Incident metering takes no account of subject reflectivity / brightness range and cannot provide the information necessary to determine appropriate film development for individual sheets.

It's the physical dial that makes a Pentax digital spot meter so useful to those practicing the zone system. Intentionally placing light readings of different scene areas on specific zones is aided by the graphic nature of the dial scales. No "doing it one's head" required. That's especially intuitive if one attaches a zone label to the meter. For those who, like me, have owned a Zone VI-modified Pentax digital spot meter since the 1980s, its zone label is likely getting a bit tattered by now. I recently found this replacement https://www.ebay.com/itm/153857811592?hash=item23d2a3e488:g:aj0AAOSwlgVeZUQ0 and installed it. I've no connection with the seller other than as a very satisfied customer.

Use of the Pentax spot meter is, unlike other more modern meters, simple and direct. It doesn't require "serving" a menu (like user-hostile digital cameras do) or a operating multiple controls. In any case, this thread is about batteries for a Pentax spot meter, not off-topic distracting discussion about the merits of one type meter vs. others. Might that be a reason why photo.net long ago ceased being the best place to find large format photography information?

As with everything in photography, it's a technical matter knowledge and understanding of which is necessary to properly use the device. It's not a "problem." I don't merely "like" my Pentax digital spot meter, I find it far superior to more modern meters that, like many overly complicated electronic devices of today, require their users to "serve" them rather than the other way around. Direct, simple operation is a characteristic of great value.

That's not the difference in question. Scroll back up and click on the link to the lithium PX28 data sheet I provided. Look at the discharge curve. Note that, as it provides its rated 160mAh capacity, voltage drops to 5.4V. Plenty of falloff to drive substantial EV error in a meter that relies on flat constant 6V reference battery output. I've always also paid attention to the initial 6.35V open circuit voltage that silver oxide PX28 batteries exhibit. That quickly falls to approximately 6.15V after a small bit of drain and stays stable for the remainder of their service life. Therefore, whenever replacing the silver oxide PX28 in my Pentax digital spot meter, I ensure it powers the LED display for a couple of dozen readings before relying on it to measure light for photography. That's all it takes to get off the starting bump and onto the flat part of its curve. Photography doesn't require absolute accuracy, but it does demand precision. Those using black and white film with a short toe and relying on this meter to determine low value exposure could easily find their negatives with no shadow density if off by 1/2 EV. Testing the entire imaging chain, then being able to replicate one's process without variation, is critical to repeatable results. I maintain that the Pentax digital spot meter, powered by a silver oxide PX28, remains an optimum way to implement such an approach.

The Pentax digital spot meter was introduced in 1977, 45 years ago. You might consider that "relatively modern," but, as I wrote more than 20 years ago in the sixth post of this thread: "...When Pentax designed this meter many years ago, silver cells were ubiquitous, and were apparently relied upon instead of including a voltage regulator. Microcircuits were not quite as inexpensive or available as today, and incorporating an IC regulator was probably overruled to make the product more marketable..." I find the advantages of this meter to more than outweigh its "pickiness about voltage." :)

I cannot explain prices on the used market, but reality is that, as I posted much earlier in this thread, the Pentax digital spot meter will change readings by 1/3 - 1/2 EV over the course of a lithium PX28 battery's rated capacity. Personally, I've had my copy for more than 30 years, and wouldn't trade its simplicity, accuracy, precision and ruggedness for any other meter.

That is incorrect. A "flat discharge curve" refers to a battery having stable operating voltage during the period when its rated capacity is being used. It does not have anything to do with how quickly the voltage drops after its rated capacity has already been used by a device. In the two decades since this thread was started, most manufacturers of silver oxide PX28 batteries have discontinued them. As a result, I'm unable to find the data sheets for them that were ubiquitous on the Internet back then. However, this one https://data.energizer.com/pdfs/silveroxide_appman.pdf shows exactly how flat the discharge curve of a silver oxide battery is. At the end of its rated capacity, a silver oxide battery's voltage drops precipitously. In contrast, the discharge curve of a lithium PX28 exhibits substantial voltage drop no more than halfway through its rated capacity. This data sheet includes the curve: https://www.duracell.com/wp-content/uploads/2021/06/PX28L_JP.pdf Since the Pentax digital spot meter includes no voltage regulation and its readings vary depending on battery voltage, I have sought out and maintain a stock of silver oxide PX28s. There are still a small number available. I relegate lithium PX28s to applications where their operating voltage can vary without negative consequences.

<p>It's me who precipitated the modern wholeplate renaissance, engaging HARMAN to first offer the film, Ebony to make the camera and Lotus (later Chamonix too) to build holders. I've used FP4 Plus, HP5 Plus and Delta 100 whole plate film in the years since then.<br> <br />I'd like to think that it was my pleas to Simon Galley that resulted in HARMAN adding whole plate Delta 100 a few years back. In my opinion, it has several advantages over the other two emulsions. First and foremost, tonality. While purely a matter of taste, I haven't found another first-tier quality film, in any format, that has a more satisfying look while simultaneously not exhibiting so much emulsion gloss that newton's rings become a problem. Then there's physical handling. Delta stays flat, both when dry (loading/unloading holders as well as into Jobo Expert drums) and wet. Moving processed sheets from drums to washer to wetting bath to hanging clips is a breeze. In my experience, the other two curl and are much more difficult to handle.</p> <p>I process three sheets of wholeplate Delta 100 in a Jobo 3005 drum using XTOL 1+3 (250ml stock solution plus 750ml water). After a 5 minute presoak, 7 minutes 40 seconds development at 75 degrees F with a rotation speed of approximately 45 rpm is my normal. This results in an EI of 160 and contrast index of 0.50. A Pentax digital spotmeter that reads exactly when used for lab-developed transparency film, calibrated shutter speeds and a calibrated densitometer were employed to reach those data.</p> <p>I've found the wholeplate Delta 100 negatives made this way print beautifully on both Ilfobrom Galerie and Multigrade Warmtone FB papers. This is the best unmanipulated film/developer/paper match I've ever achieved, and is far more pleasing to my eye than either of those papers with FP4 Plus or HP5 Plus in any of the many film developers I've tried with them.</p>

<p>The Ebony SV810 in mahogany is specified as weighing 11 pounds. I own similar Ebony cameras in the 5x7 and 6-1/2 x 8-1/2 sizes; they both weigh considerably more than specified. Therefore, I'd estimate the real weight of an SV810 is likely closer to 13 pounds. Compare that to the 7.8 pounds that my Phillips Compact II weighs.<br> <br />These are very different cameras. If carrying any distance is important to you, the Phillips wins by a mile. If you don't mind the weight (or cost!) and need more extensive movements, Ebony seems like a better choice.</p>