petrochemist

There are multiple factors that affect how visible the mesh is.

The closer the lens is to the mesh the better

The further the subject is from the mesh the better

The longer the (actual) focal length the better

The wider the aperture the better.

With a reasonably long telephoto wide open & touching chicken wire I shot this:

The mesh behind the bird is visible but I can't see anything in front.

At motorsports there is frequently safety fencing that you can't get close to (or it would provide less protection). Broadly similar settings but around 5 foot from the mesh gave:

The mesh doesn't detract too much but it can be seen

I would NEVER go for the best computer money can buy.

If you go for one that is merely good (best 2 years ago?)  you'll save an absolute fortune, and would be able to upgrade twice as often should you want to  (probably not needed).

My home computer is actually a 4GB Raspberry Pi 4 which runs a version of Linux & does most of what I need, for under £200 (excluding external drives, but including other peripherals).

The 10+ year old laptop I have is now a bit slow but will run any unusual software I want to play with.

The interchangeable T-Mount system was popular around the 1960's before Tamron introduced the Adaptall mount. T-Mounts attach to the lens via a 42mm thread with a pitch of 0.75mm, as opposed to the 1mm pitch of the M42 lens mount.

 

Now I've recently acquired a couple of what I think are T-Mount lenses, but the mounting thread is larger, more like 46mm. Is this still classed as a T-Mount? And are the larger thread T-Mounts available anywhere?

 

Thanks in advance.

No not T-mount, I've heard Hanimex had their own variant adaptable mount. I don't think I've come upon any yet. Perhaps I should double check my Hanimex & Palinar lenses :)

FWIW T-mounts are still popular for mounting to telescopes (& to a lesser extent microscopes) but more commonly known as T2 now - I don't think there's any difference in thread or registration officially the T2 allows orientation to be adjusted, but the names seem to be used interchangeably.

And that is what you want the polarizer to do. If not, the choice is not to add exposure (and overexpose the unaffected part), but use less of the polarizing action. Or none of it.

Indeed it's what you what you use it for, but it's effect does require the effect to be compensated, or the pond floor will be invisible.

Hi all I understand that it is not ok to use an analogue polariser on a digital camera but is it ok to use a circular polariser on film ?.

Peter.

As far as I know there is no such thing as a digital polariser. Newer filters sold for digital may have better coatings but they still polarise light using real light before any digital to analogue conversion. Polarisers themselves can be high extinction or high transmission types, then there is a linear/circular choice depending on if a quarter wave plate is added. It doesn't work well combining two circular polarisers (at least unless you switch one round - two CPLs back to back give very weird effects, front to front they can work like a variable ND).

You can get perfectly good results using a 50 year old linear polariser on a digital camera, my grandfathers old 'pile of plates' polariser (probably over 100 years old) would also work if it was a bit wider - less than 1/2" diameter is just too small for my lenses.

FWIW circular polarisers came out long before digital photography was practical, yes they work fine with film as that's what they were originally made for! I think my first CPL was brought in the mid 1980's

I use the fixed correction factor that is usually printed on the rim, and nothing else.

And the answer is no. Do not compensate for the variable effect of the filter. See my earlier reply.

Usually the effect of the filter is small enough that you don't need to allow for it, but if a significant amount of the incoming light is all polarised in the same direction you may need to compensate if not using TTL metering (self compensating)

On occasion I've had reflections from water that provided far more than half of the light. Arrange the polariser one way & expose for the reflection, twist it by 90 degrees & you have to expose for the dim pond floor...

There's always macro of items round the house:

Watch Macro by Mike Kanssen, on Flickr

A pic taken with the FD 500 mirror lens, on a Leica M240. Lens on tripod. I forget what ISO I used. The donut highlights are subtle, but there.

I wouldn't call those doughnuts subtle, but the subject is attractive enough to make them bearable!

I have taken a few where the bokeh is more distracting, but the vast majority it hardly shows at all.

I would roughly estimate the focal length of the front part only as 4 inches. The rear part on its own has a focal length of around 1.5 inches. With the two together, it's around 2 inches from the centre point of the combination to an image of a distant object (at last, the Sun). The image being very close to the rear glass.

 

Another point - I don't think the box, marked TAYLOR-HOBSON, is original to the lens, marked TAYLOR TAYLOR & HOBSON. Also the box is somewhat larger than the lens body, it would roll around without some additional internal packaging, of which there's no sign.

Reading you first post again I suspect it's actually a 35mm lens designed for 16mm film format. Cine projector lenses frequently have extremely short rear distances and the parts separating could be just a focus mechanism. Removing a group of elements for a lens design often gives another usable lens which typically has uncorrected aberrations - giving rise to your lovely impressionistic results.

I wonder if 16mm and 35mm, rather than focal lengths, refer to the two different film formats. I've got a more recent Rank Taylor Hobson projection lens, which is marked "Supertal 16mm 2 inch f/1.6". Suggesting that the 16mm (and 35mm) on the earlier lens does refer to the film format, although it's strange that focal lengths aren't marked. But I'm only guessing, I can't find any information online at all.

Whilst reading your first post I thought it was 16mm format & 35mm focal length, but the two part design does pretty much rule that out. I think formats could easily be the meanings

It's very difficult to judge focal length with macro subjects, & projector lenses can have very short rear focal distance (infinity focus probably impossible).

Can you estimate the focal length by (unmounted) comparison with other lenses?

A very generous offer Stan.

I'd probably find several of them useful, but I'm in the UK so postage would no doubt be significantly higher :(

How many trade secrets do you keep? Most of us, if not all of us, are happy to share our knowledge with newcomers to the craft. However, I think most of us have one thing that we keep to ourselves.

 

In my case, it's a manual focus lens that I use adapted to a mirrorless camera. It's a very minor thing, but I find it fun, knowing that I'm keeping it to myself. Needless to say, it cannot be revealed via metadata.

 

What about you?

If I keep secrets it's because I can't remember myself, legacy lenses & filters (I often shot IR so filters are important) can both fall into this category, if I don't note them down quickly.

Huh?

 

Just to name one, the Olympia Sonnar 180mm for the Contax, 1936 (Zeiss Contax RF Olympic 180/2.8)

I've always heard that the longest focal length contax lenses required the Flektoskop, Flektometer or Panflex mounts which add a reflex viewer, effectively turning the rangefinder into a SLR.

As well as many printed sources over the years claiming rangefinders were limited to 135mm for focusing reasons (it would take me years to find them) this can be found at Contax rangefinder

If this is inaccurate perhaps the Contax, which is often acknowledged as the best rangefinder managed to stretch things somewhat, with really top grade hardware.

In P mode the camera decides aperture & shutter speed to give good exposures according to parameters the manufacturer set.If the light is sufficient to achieve reasonable shutter speeds the aperture will often be closed to increase DOF.

Like Joe I don't use P mode, I usually fix the aperture & let the camera sort out shutter speed to match, so I've not become familiar with how my different cameras tend to behave when left to their own devices.

L39 screw mount lenses typically have a short flange to film distance, which precludes the insertion of a mirror box and mechanism. At least that's my explanation.

Not just typically, it's one of the features that DEFINES L39. The L denoting Leica and indicating a rangefinder mount with 28mm flange distance.

There have also been other M39 rangefinder lenses with slightly shorter flange distances but these were never really popular. Mine was relatively easy to modify so they can be used on L39 bodies/adapters.

There are SLR cameras that use the same M39 thread, but with greater flange distance (sometimes called Z39 for Zenit m39), using L39 lenses on these limits you to close-up shooting as the lens will be about 20mm further from the film than it was designed for. One possible partial exception are the retractable 50mm lenses like the Industar 10 - I think these when not extended are close to Zenit m39. Of course when retracted the rear of the lens will foul on any SLR's mirror so they could only be used with extreme care using mirror lock up.

Then there have been enlarger lenses using m39 threads too - these have no fixed flange distance.

Range finder lenses are not made in focal lengths greater than 135mm, with one of these mounted on a Zenit m39 body the maximum focus distance is about 1.6m, any shorter focal length will focus closer still.

I like to use enlarging lens which has no focusing helicoid thus the need for the bellow. The bellow is for focusing but a totally colapsed bellow is still of some length. I would like to have this length as small as possible so that I can focus to infinity on more of the enlarging lenses.

I find helicoids are much better for this. (I see @mike_halliwell has already suggested them) There are now a wide range sold in M42 mount as well as short M42 adapters to fit them on mirrorless bodies. My shortest helicoid is only 10mm long, and I have others out to 90mm.

All my sets of bellows foul on the flash bump of several of my cameras so often need extra extension.

Fresnel by Mike Kanssen, on Flickr

or

Crystalised light by Mike Kanssen, on Flickr

No so significant but this view from my bedroom window shows a scene sadly no longer visible - the view of the fields being completely blocked by new houses.

ultra flashgun by Mike Kanssen, on Flickr

I never did work out the guide number of the lightning strike.:)

Taken me a while to get this one on-line but at last here it is:

Crystalised light by Mike Kanssen, on Flickr

720nm IR with a 500mm mirror, sorry the subject only has a 70-210 IIRC.

Nikon Shooter by Mike Kanssen, on Flickr