petrochemist

From the fact you're asking about both together I assume you mean the type of converters that screw on the front of the lens. Both halves are needed to get the 'fisheye' effect (often just a wide angle converter), With the outer part removed it is a close up diopter giving a macro/close focusing effect. These converter systems vary in quality, most I've tried have been pretty poor giving images that print OK to 6x4 or 7x5 as my film shots used to be most of the time. Printing to A4 their quality disappoints. There are a handful that are much better but even these do not compare to proper dedicated lenses. If your camera is a fixed lens model then they do increase your options. The fisheye should give a very wide FOV around 180° often as a circular image. For many interchangable lens camera systems there are cheap third party true fisheye lenses (not converters) that will only cost around $50 and will give MUCH better quality. The macro function makes the lens focus closer for photographing small items (distance focus is lost unless the fisheye part is fitted). Dedicated macro lenses tend to be more expensive but there are other close up diopters that are significantly better quality - I'd recommend the Raynox DCR150 (again around $50) How close your lens will focus will depend on the strength of the diopter with the DCR150 focus will be about 0.2m & somewhat closer as the lens is focused. It's stronger brother the DCR250 will not focus beyond 0.125m. I don't know the power of the macro part of the fisheye converter you've seen so can't quantify the focusing range on that. Both fisheye & macro shooting can work brilliantly in B&W especially if the photographer has suitable knowledge on using colour filters for contrast (usually now done virtually when converting a colour digital image to B&W so it's not required to be able to physically fit filters). About ten years ago I had a brief play adding an IR filter between the lens & a fisheye converter it focused OK so if shooting film physical filters can be used with these converters. I never took it beyond proof of concept having much better solutions for both macro & fisheye.

Simply removing the color information is a very long way from goof B&W conversion. Once you've had a play with Niks Silver FX you soon learn how much more can be done. Virtual filters can be used to alter the relative darkness of regions based on their color.

Assuming you are already a photographer: As you've probably realised the camera is totally manual with no automatic features at all. The camera as shown is still partly closed up, the front standard (holding the lens) needs to be moved forward along the baseplate - there are often a couple of catches that need to be pinched to allow this. On folding cameras focus can sometimes be controlled by how far the lens is moved along the baseplate (I think the case here) or sometimes there's just a single outer position & focus is done via rotating the inner part of the lens (the ring directly outside the glass element). Usually in the second case there are distance markings on the lens which I can't see here, which is why I think it falls into my first class. There is a small lever (with triangular pointer) at the bottom edge of the lens that adjusts the aperture ranging from f/4.5 to f/32 in this case. The outer ring round the lens adjusts the shutter speed from 1/300s to 1s, along with B for while the shutter release is held down & T requiring one press to open the shutter & a second to close it again. The two levers visible on the left are the shutter release & a cocking lever. The shutter will need to be cocked before the release works. It looks as if your camera has two viewfinders, a prism for looking down & shooting from the waist, & a fold out sports viewer on the right of the image. I would recommend at least a half hour playing with the settings before loading the film.

Motorsports & fireworks are two examples where I nearly always use longer shutter speeds, freezing a racing car tends to make it look parked. Flowing water (with splashes) is a subject that IMO can work very well in either, Other landscapes, macro, portraits & still life are not typically good with motion blur - but if there is motion in a part of the image relative to the rest it can be shown to good effect. Imagine trying to take an image of a typist to show their hands blurring but their head sharp. With a typist like me (slow) the head will move too much & I doubt anyone could get it to work. Some touch typists I've seen barely move their heads & their fingers seem to fly with the right speed this can be shown. :) One of the big advantages of digital is the ability to try things that you don't think will work it doesn't cost anything to take extra shots at different shutter speeds (or other settings). I've often taken shots where I pushing the limits of what is expected to work (like handholding for half a second) yes most of the time these go straight in the digital bin, but just occasionally they work out & give results you couldn't have got otherwise (or needing the tripod you'd left in the car 2 miles away) Imagination can give some hints of what MIGHT work, and experimentation can then hone in on the settings that gives the desired effect or shows it doesn't work for other reasons. Depending on the reasons it didn't work changing the set-up/lighting might give rise to another round of experiments.

IBIS doesn't help with subject movement either :)

There are multiple options for low light situations, but each has disadvantages. There are occasions where adding light doesn't work. Astrophotography would be the most extreme example, but it's also the case when you want to preserve the atmosphere of a night scene, or where the flash would be a nuisance of cause potential damage... Fast lenses give less DOF when wide open for light gathering. Often this makes them unsuitable. Long shutter speeds can be an answer, but can cause issues with moving subjects. High ISO is probably the most flexible but push it too far & noise becomes a serious issue. Many scenes need a carefully balanced mixture of all these approaches. As far as the A7iii & A7siii go both are way outside my budget & will be for years. I don't shoot a huge amount of low light stuff, but would still prefer the s model the sensor resolution of this will be more than I need and the extra sensitivity will be useful occasionally. I've managed to find occasions with my existing cameras when f/1.2 isn't as fast as I'd like, even though it's DOF is non-existent, with longer lenses I have to make do with slower options - none of my 500mm options are faster than f/5.6, and focal ratios just get worse as I move into really long optics. Whichever body I'm using their will be a place for fast lenses, but most of the time weight issues will ensure I only have more normal options available.

Low pressure sodium lights are one of those whose light can be removed fairly effectively using a filter that is reasonable clear to the eye. Neodidyium (red enhancer) filters remove a number of fairly narrow bands that happen to include the prominant sodium D lines. It's the only example I can think of, that uses reasonably afforable filters to block emission lines :)

I 've only deliberatly shot video on two occasions. It's not a medium that appeals to me. Wrapping something around the back of the holder would be an answer certainly but i don't play with extreme ND often enough for me to sort it out, all my IR filters are screw types which don't need the fix.

Many photographers would class Cokin filters among the 'cheaper knock-offs' because all their filters are resin based. My own experience of them is they generally work perfectly well unless they are very badly scrached. There are hoods and caps made to go on these cokin mounts, not as useable as the typical OEM ones but not totally useless. I've definitely seen light leaks round the back of filters in cokin holders, which is one of the reasons I prefer screw ons.

In case my memory might be wrong i checked emission lines are typically quoted to 0.0001nm Theres a list of the strongest emission wavelengths for lead here. (Listed in Angstroms which are 1/10nm) :rolleyes:

Thats far more down to how WE see light than the nature of light. Humans have 3 colour light receptors in our eyes, Other animals can have more or less than us I believe there are mantis shrimps that can see 13 colours. There are alos metamers different combinations of colours that LOOK the same to humans even tough they are quite different in composition. At work we have instruments that will differntiate light to much closer than 0.1nm giving rise to thousands/millions of distinct colours of light. I remember some atomic emmision lines having wavelengths specified to less than 1/1000 of a nm (Visual light being roughly 400-700nm). If working with paint or other absorbtive media the human three primary colours are not RGB at all. Red, blue & yellow where those taught at art classes when I was at school, Yellow, cyan & magenta are thos ecommonly used in printers (together with black & often lighter shades of each of the printing primaries)

Yellow filters (as well as orange & red ones) are usually long pass filters transmitting light of longer wavelength than yellow (between ~450nm & ~480nm depending on the filter). The only exceptions I know are yellow colour correction filters like the Wratten #6 which (My Kodak Wratten handbook doesn't show the spectra for this filter but specifically states it's not a longpass type). For those interested the handbook is available on-line here I find it a great reference, but I have a strong technical bent. Even short pass filters designed to transmit only wavelengths below a set value frequently have overtone transmissions well above that value. This becomes a problem for those wanting to record UV images with converted cameras, all the cheaper UV transmitting visual blocking glasses such as Schott U330, BG3 etc. leak considerable NIR something those converted cameras are very sensitive to. Special coatings have to be added to the filters to block these overtones resulting in filters costing hundreds of pounds. In the case of U330 the overtone transmission reaches about half the transmission of the main band (45% vs 88% on my copy) and transmits over a wider range of wavelengths. Filters rarely block all the light from their excluded wavelengths and never transmit all the light from the transmitted wavelengths (the best transmission I've managed to measure on our works spectrometer is 98%). Transitions from permitted to excluded tend to be reasonably gradual most of my longpass type take over 40nm to go from 1% transmission to 50% transmission, in the case of the 950nm filters this takes around 150nm! Alan's less technical summary is pretty accurate for the actual use of filters, though I feel his description of polarisers is missing out on half their uses. Polarisers set correctly can be used to BOOST reflections something I use every bit as much as their reflection killing properties. :) In everyday B&W photography yellow, orange & red are used to progressively darken skies (making clouds more visible even where a polariser can't manage this) Green filters are used for skin tones, or for brightening foliage compared to the remainder. If there are any strong colours present in the scene they can be darkened by using a filter of the complimentary colour. The best way to explore the behaviour of coloured filters is to convert colour images to B&W using software like Nik's SilverFX, where each colour of filter can be virtually applied at varying strengths simply by playing with sliders.

Media is simply the plural of medium, there are cell growth media, storage media, as well as the news media... I would consider the manipulation of photographs that goes beyond photography to be 'graphical art'. Where the line between photography & graphical art lies is a matter of continuing debate :)

If you have no plans to get a lens with a bigger thread & it's just keep your options open the hassle of using stepping rings, not being able to fit the normal hood etc. is IMO enough to make it a bad choice. If this is your situation I'd certainly go for a 58mm filter. If on the other hand you are hankering after an ultra wide, or faster lens there may be some benefit in going larger - but only if you know which filter would be right for this later purchase, and you feel it's a wish your likely to fulfil. Shooting with full spectrum converted bodies I use filters quite a bit. I have lenses ranging from under 25mm diameter up to 96mm diameter. In addition some of the filters I use are only available as ultra expensive special orders in sizes above 50mm - for some of these I have to make do with 25mm & select lenses appropriately. So a one size fits all approach is just not practical for me. :) Fortunately several of my lenses with 37mm threads don't vignette noticeably with a 25mm filter fitted. I have a range of preferred filter sizes & will generally use stepping rings to get to those. My current favourite sizes are 37mm, 52mm & 77mm but I admit I have lots of filters in other sizes being prone to trying out any cheap unusual filters I see no matter what size. Occasionally this will have me looking for better quality versions in my preferred sizes. I rarely use filters on my very largest lenses except by simply holding a square filter in front of the lens.(not good for long exposures).This is partly from the cost issue you've highlighted.

'Occasional work' as an amateur, suggests to me the camera is fairly incidental. The Z6 is a high end camera well above the level of any of those I use for my amateur photography. You've not specified the type of photographic work he does. I wouldn't want to try weddings with my hardware (all 5+ years old) as these are once in a lifetime events where failure is simply not an option, but just about any other type of photography old kit would still do the job perfectly well I can't help but think the purchase of a Z6 7 associated lenses, might be responsible for his dept..

Thorium 230 has a half life of 77000 years & Thorium 232 has an even longer half life (14,000,000,000 years), there's not much difference in the composition after only 50 years. Immediate daughter decay products also have long half lives (Radium 226 is 1620yrs giving of alpha & gamma, Radium 228 is 5.8 years emitting beta) Lenses with high activity through lead bricks have almost certainly been contaminated by other radioactive material since being made, that sort of signal would not occur from pure Thorium after only 50 years (which is less than 1/1500 of a half life, even for the less stable form). In this time less than 0.05% of the initial thorium has decayed. If such a lens exists chances are someone has decreed 'the lens is radioactive so it must be stored with other radioactive material'. In the sort of location this could happen the radioactive material it's stored with could be MUCH more radioactive than the lens itself. Surface contamination is the main reason I'm involved in radioactivity (site deputy radiological protection supervisor), Ash & sludge on site concentrating up trace NORM (naturally occurring radioactive material) to the point it falls within legislation. Radioactive lenses are more active than our NORM, but they don't spread nearly as easily. I'd be happy to spend the rest on my life with a typical radioactive Takumar in my bedroom (except when I take it out to use).

Changing your system to Nikon's FF options in DSLR or Mirrorless variants will be expensive. I'm not convinced it will be a noticeable 'upgrade' for you. I personally find mirrorless better for most of my shooting - I use 3 mirrorless systems but only one DSLR system :) However I like using adapted glass & shoot quite a bit of IR, both places where mirrorless excels. In everyday shooting I doubt anyone could tell from an A4 print which of my shots were taken with FF & which with MFT (and in my case the MFT cameras would be older as well as having a smaller sensor). Sensor size can help but it's not as significant as many want you to think.

PCB detail from an old mass spectrometer by Mike Kanssen, on Flickr

And yes You're both right!:oops:

If it's 'plated' it would be galvanised (tin plated) and would have a different look to stainless. Far more likely is that it's the low grade stainless being discussed here.

Watching the action (IR) by Mike Kanssen, on Flickr

Rufus resting by Mike Kanssen, on Flickr

sml P1150595 bw by Mike Kanssen, on Flickr

seafront garden aerochrome small by Mike Kanssen, on Flickr