rodeo_joe1

The usable capacity of any rechargeable cell varies with the discharge load/current. Manufacturers baldly quote the best case scenario without necessarily disclosing the details. It might be a load of a few kilohms over many days, or a few ohms over a matter of minutes - who knows? But both cases almost certainly won't multiply out to the same milliampere-hour figure. Unless you have a multimeter with a data output, together with a computer datalogging application, your plan sounds like a tedious way to pass the time!😵

Hasn't this been discussed here? Personally, I think both time and film are too valuable to fritter away trying this, that and the other developer. It's well known that contrast is easily varied in proportion to development time. So isn't it easier to simply adjust the time in a known developer rather than formulate a new one?

Here are some comparisons of centre versus corner resolution with Planar-type 50mm lenses on the 35mm format. Expect an 80mm lens on 6x6cm to behave a bit worse, because the corners are 3 degrees further off-axis. New style 7 element West German Zeiss Planar @ f/2.8, centre - And corner - CZ Jena Pancolar - an old style 6 element Planar copy @ f/2.8, centre - And corner - And the corner @ f/4 - Now re-focused for best corner definition; showing that there's quite a bit of field curvature - BTW, these are 100% crops from a 60 megapixel digital camera. On film you'd be hard-pressed to resolve the 100 lppmm bars at all.... but if someone wants to give it a try, go ahead!

All lenses have inferior sharpness wide open and away from the centre of the frame, often becoming noticeably blurred in the corners. That's assuming they don't suffer from curvature of field, which is another big assumption. Worrying about corner sharpness at f/2.8 is a wild-goose chase.

I like the colour rendering, but performance wide open, especially edge and corners, is a bit disappointing considering it's a 7 element design, rather than than the usual 6 elements of an f/1.8 50mm lens. Res chart results show it performs about the same as a 6 element East-German CZ Jena Pancolar of the roughly same vintage. In fact the Pancolar might have better corners and a bit less central LoCa. More pixel-peeping required to confirm that. Bonus Pic-

Well, it appears that Selenium cells aren't an obsolete and dead-end technology after all. Link.

It's not just grain. All the fine detail has been blurred away - the fronds on the spikey leaf and the centre of the flower for example. Like I said, pixels ain't necessarily resolution, and if the CRT scanning spot diameter is bigger than the pixel spacing, then the number of pixels outputted isn't worth very much. Using a slower film or a larger film format may well reduce the granularity, but it won't bring back detail lost to a slightly de-focussed CRT.

Both depth-of-field and depth-of-focus make assumptions about lens behaviour and human vision: 1. That real lenses behave like a 'thin lens' model - having zero distance between front and rear nodes. 2. That a lens has no aberrations, especially spherical aberration, and projects a perfect cone of light from each infinitely small point on the subject plane to an equally small point in the image plane. 3. That diffraction of light plays no part in image sharpness 4. That human vision is consistent in tolerating a certain limit of blur, called a 'circle-of-confusion', which in turn is a cross-section of the aforesaid perfect cone of projected light. If we take all those assumptions as being representative of real-world lens behaviour (ahem!) then we can formulate the point of intersection of an imaging-plane (i.e. Film or digital sensor) with the projected light cone at other planes of focus. Planes resulting from a change of subject distance - depth-of-field - or a misplacement of the film or sensor from the true image-plane - depth-of-focus. Depth-of-focus is easier to calculate because it's symmetrical about the point of focus. So, if we set a limit to the acceptable cone diameter - the circle of confusion - and we know the lens aperture number ( = focal-length/physical lens diameter) then we can work out how far from true focus the film or sensor is allowed to be. To a first approximation this simply = C-o-C * f-number. Plus or minus depending on whether the true focus falls in front of, or behind, the imaging plane.

Does YongNuo give any facility for a firmware upgrade on that flash? If so, maybe there's a firmware revision available. Otherwise you're probably stuck with the issue. It sounds like some component is latching in the on state. And without knowing the flash/camera hardware, and the comms protocol between the two, it's impossible to guess at a cure.

And ear-defenders to go with it! Before H&S was such an issue, I was required to use a Littlejohn copy camera with a huge vacuum platen - 24" by 30" or some similar ridiculous size. When the pump was turned on the noise of air being sucked into dozens of tiny holes was pretty deafening in the small darkroom that formed the camera chamber. Great memories... I think!

Absolutely no sign of gold being used on any of the Weston or Sekonic cells I've seen. The contact ring is a sputtered silver-coloured metal - maybe a sintered solder-like alloy. Certainly soft enough to deform under strong contact pressure. Gold? Nary a sign of it! Also, AFAIK, the industry preference for a transparent-but-conductive coating is to use tin, which is cheap but effective. The contact ring on the Weston/Sekonic cells might well be pure tin, come to think of it. That would make sense. Incidentally, Selenium is nasty stuff that can give one chronic halitosis if ingested even in tiny quantities. It stinks like rotten cabbage at single figure parts-per-million dilutions if vaporised. Small wonder it's seldom used today.

Margo-brooder1 was last seen January 24, 2013 two days after posting. Another dedicated hit'n'run member.

Not hard to find unless it's a rare or obscure camera mount - Nikon pre-AI with 'rabbit ears' for example. The big drawback these days is the cost if you need to swap the adapter on a used Tamron lens. The adapter might easily cost more than the lens!

From my measurements of the Yashica-mat and Mamiya (~0.5mm) and Rollei's spec of 0.45mm, the free space is clearly a fair bit more than 3 or 4 thou. It's between 0.2 to 0.25 mm, or about 8 to 10 thou. FWIW: Depth-of-field tables won't give an accurate assessment of film-plane displacement blur, which is a depth-of-focus issue. There's a subtle difference between depth-of-field and depth-of-focus, whereby D-o-Field is very dependent on subject distance, while D-o-Focus is not. A film-plane displacement will indeed cause a shift of focus, but the degree of blur can't be given a fixed field depth because it varies with the subject distance. As you say, the tolerable blur is given by the f-number * whatever acceptable circle-of-confusion is chosen. Conventionally it's about 0.053mm for the 6x6cm format. Which gives a film-plane tolerance of +/- 0.148 mm @ f/2.8, well less than the (at least) 0.2mm of slop that many cameras are machined to! Who mentioned a cross-wise curve? And does it matter? A displacement from flat is relevant in whatever axis. However, the squashing of a naturally curling film by the pressure-plate (the pressure coming from the film itself) will constrain the film to the plate-distance, minus the thickness of film+backing paper, over a considerable area of the frame. So it's not a problem if the focal plane is calibrated to that distance. It could only be an issue if, for some weird reason the film decided to bulge toward the lens. - Hasselblad, please take note.

Some pix trying out a Rollei-fit West-German Zeiss 50mm f/1.8 Planar on the Sony A7r4 -

Never heard of it, but this is the first 'fail' I've had using white-spirit to soften and remove sticky-label gunk. I think the double whammy of white-spirit followed by meths worked by a lucky chance. Because meths on its own isn't usually very successful with label adhesive. Then again, I've never had to remove gum quite so age-hardened before.

Taken with a recently acquired Minolta SrT101 + 58mm f/1.4 P-F Rokkor. F/1.4 F/2 F/4 Film was T-max 100 in T-max developer. Sorry about the rather sombre subject matter. It was freezing cold and getting dark, and the old cemetery is the nearest source of interesting pictures.

Kodak Alaris's tech pub for Flexicolor is readily download able and pretty plain. Page 1-5 is specific to the small/rotary tank 1 US gallon kit. It says the bleach is to be used straight, i.e. without a starter. It's only the commercial-size bleach replenisher, available in 5, 12.5 and 75 US gallons, that needs a starter.

No offence meant Jean, but I'm pretty dismayed and horrified at a popular taste that requires 5.7 million people to view that - or 5.7 people a million times each.... plus a few more after this thread!

..... NOT! Where do you stick the price label on a used filter? Why, right in the middle of the glass of course, and on both sides. Then you let the adhesive harden off for a year or more in a hot display case. Well, that's what a local Buy'n'sell shop did anyway. They had a 'giveaway' sale of a couple of lens filters for £1 each. One of which was an 82mm Hoya UV(0). I obviously couldn't pass it up at that price, regardless of the price sticker placement. What I didn't realise until I got home was that there were actually 4 price stickers stuck to it, one on top of the other on each side of the filter. The lower ones of which had been there so long that the 'sticky' was no longer sticky, but rock-hard. Leaving this residue on the glass - Lovely! And that was after an initial cleaning with White Spirit. (Not my usual treatment of a filter I hasten to add.) White spirit usually removes label gunk with a single wipe, but not this time. I had to resort to a second rub-down with Methylated spirits to shift the stuff; rubbing much harder and longer than I cared to with several lens tissues. Surprisingly, the filter's blue AR coating and glass survived the attack pretty much unscathed, and I've seen much worse filters offered for sale as in 'good optical condition'. My £1 outlay wasn't a big risk, and safely removing the adhesive residue was an interesting challenge, but really; what kind of shop-monkey thought it was acceptable to rub price stickers hard down onto a camera filter? The vandal had even taken care to place the labels exactly co-incident with each other on both sides of the glass! Could have been worse I suppose. The stickers could have been on the front element of a 300mm f/4 lens costing several hundred £.

I agree that old Weston meters have a charm and both a visual and tactile appeal. As far as reliability is concerned - just some observations from my experience with them. Some may dismiss 'anecdotal' accounts, but if you see enough meters a pattern tends to emerge. Personally, I've had more than a few Weston Masters pass through my hands to see a pattern. Speaking from that experience I would say that the 'iconic' status of Weston IV, V and EuroMaster meters is decidedly undeserved. All of Weston meters from the mk iv onwards were fitted with an inferior selenium cell that almost invariably loses sensitivity after a few years. A bold statement, but witness all the previous posters that say their late-series Westons have had to be re-celled (a service that's no longer available). I can add the dozens of later series Weston Masters I've looked at and rejected - being simply 'dead' or abysmally failing a simple accuracy check. My lengthy search for a fully operational 'mint' Weston V proved fruitless, and I gave up the search years ago. OTOH, I have a small collection of Weston ii and iii meters that are all working perfectly. A comparison of the selenium cells between early and later models shows a clear difference, both in cell colour and in the thickness of protective varnish applied. With the newer cells having a blue, rather than brownish colour and a barely visible (non-existent?) protective coating applied. In short; Weston's older cells are far more robust and long-lasting. So if you're in the market for a Weston meter, get a mk-iii. That was the first model to be calibrated in ASA/ISO speeds, and the last to use the decent brown selenium cell. Downside is that the incident light kit - consisting of both a diffuser and range shifting ND filter - is difficult to find. WRT to poor cell contact: the cell in all Weston Masters is firmly held in place by a strongly-sprung contact ring. It does not work loose unless the meter has been severely abused. It certainly shouldn't be loose to the point of moving at a finger tap. However, the contacts may oxidise over time, but this is usually easily fixed by gently pressing on the plastic dimpled lens over the cell and giving a it a slight twisting action. OTOH a poor connection or sticky action to the mechanical meter movement might well respond to a gentle knock, but would indicate that the meter movement needs attention - cleaning probably. My advice would be to steer clear of Weston IV, V and Euro Master models. And of any meter with a moving-coil indicator in general. There's too much to go wrong. Old electrical equipment of any sort is generally bound to fail eventually, and newer gear is usually far more reliable... getting less so with age.

Probably not. As I said, even processed film still has the same tendency to curve inwards to its emulsion side. It takes quite long storage inside a negative sleeve in a folder to flatten it, but as soon as it's released from its prison it starts to acquire a curl again. I spent years in darkrooms wet-printing, and in all that time I never saw a piece of (thin base) film that wanted to curl away from its emulsion side. It's always, however slightly, concave on the emulsion side and convex on the base side. Given that tendency, I'd say the chances of the film going flat of its own accord in a loose channel are zero. My best guess is that its natural curve away from the lens is simply restrained by the 'pressure' plate. Resulting in it touching the plate in the centre region of the frame, and bowing away from the plate at the sides in order to follow the film path. OTOH, the Mamiya 645 film-path bends the film tightly back over rollers, against its natural curl and immediately before the gate. There are also sprung pin-rollers on the emulsion side of the film at either end of the guide rails. Without microscopic examination of a film within the camera, I surmise that this does indeed keep the film flatter in the gate. However there's still that 0.5mm gap for the film to do whatever it likes. Like I said at the very start - it's film! It's flexible and has an emulsion thickness. So ultimate accuracy and precision of the image-plane isn't its forte. It's a fairly approximate medium.