Olympus UK E-System User Group
Olympus UK E-System User Group

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Search: Posts Made By: Petrochemist
Forum: Nostalgia Nexus - early and pre-digital discussion 1 Week Ago
Replies: 18
Views: 744
Posted By Petrochemist
Re: Thornton Pickard 5x4" half-plate view camera?

I believe symmetrical lens designs could be quite high quality, many of them are still quite usable today (at least by those of use who don't obsess about sharpness)


Ansel Adams certainly got...
Forum: Nostalgia Nexus - early and pre-digital discussion 1 Week Ago
Replies: 18
Views: 744
Posted By Petrochemist
Re: Thornton Pickard 5x4" half-plate view camera?

These massive cameras weren't the norm in the 1930s, they were more routine prior to the release of 120 (& similar) films (around 1900), but still offered considerable advantages for those wanting...
Forum: Nostalgia Nexus - early and pre-digital discussion 1 Week Ago
Replies: 18
Views: 744
Posted By Petrochemist
Re: Thornton Pickard 5x4" half-plate view camera?

Modern large format lenses are all sized for Copal shutters, which probably wouldn't work well with this. They have elements either side of the shutter.

If you can identify the thread on the lens...
Forum: General photography discussion 2 Weeks Ago
Replies: 13
Views: 404
Posted By Petrochemist
Re: Mapping/ aeriel photos

I've stitched several composites of 6 to 10 images from moving ships using ICE. All handled automatically, the only significant error being on a join that was 80% water & 15% sky - not leaving it...
Forum: Lens focus 24th November 2018
Replies: 10
Views: 1,162
Posted By Petrochemist
Re: Lenses: relative length & diameter

There are a couple of crafty lenses designs that were invented around 100 years ago:
Telephoto lenses use a design that allows the lens to be physically shorter than it's focal length. Today the...
Forum: For sale or wanted small ads 14th September 2018
Replies: 21
Views: 1,383
Posted By Petrochemist
Re: E-M5 MkI converted to IR

Nearly all the long pass IR filters I've looked at transmit at least 90% from around 20nm above their listed cut off. So the usual loss would be around 5% (1/10 stop). I think the only exception has...
Forum: General photography discussion 20th July 2018
Replies: 34
Views: 2,381
Posted By Petrochemist
Re: Pinhole digital photography

Pin hole images tend to be very soft on small sensors. I've tried them on both APSC & MFT and the results aren't impressive. Even so they can be interesting to try.
Forum: Foto Fair 10th July 2018
Replies: 15
Views: 609
Posted By Petrochemist
Re: Next door neighbours lawn mower

Nice series.
I particularly like the 5th, 12th & 13th
Forum: Lens focus 3rd July 2018
Replies: 20
Views: 3,628
Posted By Petrochemist
Re: m4/3 lenses for IR

I've used the Panny 14-42, 50-200 Olympus 9mm BCL & 17mm/2.8 for IR without any hot spot issues on my converted camera.
But I have seen hot spots with the 14-42 when shooting IR on a non-converted...
Forum: Converters, adapters and extension tubes 27th June 2018
Replies: 17
Views: 2,279
Posted By Petrochemist
Re: Polarising Filter

I always find it odd that photographers concentrate on the reducing reflections aspect of polarisers - I often find using a polarizer to increase the reflection works well too. Boosting reflections...
Forum: Accessory talk 27th June 2018
Replies: 4
Views: 1,477
Posted By Petrochemist
Re: IR screw-in filter supplier recommendations?

Nearly all the IR filters I have are cheap Chinese ones (650nm, 680nm, 720nm, 760nm, 850nm & 950nm as well as a variable wavelength one). They seem to work just fine, certainly the spectral effects...
Forum: E-System User Group goodies 12th June 2018
Replies: 6
Views: 3,217
Posted By Petrochemist
Red face Re: MF adapter / Sunagor lens.

Ah, yes I clearly need to pay more attention.
Forum: E-System User Group goodies 11th June 2018
Replies: 6
Views: 3,217
Posted By Petrochemist
Re: MF adapter / Sunagor lens.

I'm not totally sure these are quite the same brands as I brought, but they should be equivalent anyway (they look the same):
Helicoid ...
Forum: Software 3rd May 2018
Replies: 6
Views: 1,200
Posted By Petrochemist
Re: DXO apparently in trouble: Nik???

FWIW you can also call those same standalone versions from FastStone, again not as smooth as running from Photoshop, but avoids the monetary outlay & works reasonably well...
Forum: The lounge 18th December 2017
Replies: 18
Views: 695
Posted By Petrochemist
Re: DNA testing anyone?

My research into my own ancestry has failed to get any documented proof of links to the beaker folk. Despite this I don't see any reason to find it worrying, tracing the origins of man further back I...
Forum: Foto Fair 9th December 2017
Replies: 4
Views: 328
Posted By Petrochemist
Re: Bright Moon

The tripod might not be necessary if you can find a good well braced spot. at least if that's 1000mm equivalent. I've shot the moon braced in a doorway with a 600mm mirror lens mounted via a focal...
Forum: Foto Fair 1st December 2017
Replies: 15
Views: 966
Posted By Petrochemist
Re: Unintentional success

It does have a nice dreamy quality.
Perhaps something along the lines of 'xxxxxx dreams', but I can't get you nearer than that.
Forum: The lounge 24th November 2017
Replies: 122
Views: 4,921
Posted By Petrochemist
Re: Bloody cars !

Super unleaded will be about as likely to contain ethanol as ordinary unleaded. Ethanol is the most common of several bio components that can be used - both fuels must contain at least 5% bio...
Forum: The lounge 22nd November 2017
Replies: 122
Views: 4,921
Posted By Petrochemist
Re: Bloody cars !

The link you were seeing between octane & volatility was misleading, possibly due to the reduction in benzene contents of petrols. Octane rating has complex causes but some predictions based on...
Forum: The lounge 22nd November 2017
Replies: 122
Views: 4,921
Posted By Petrochemist
Re: Bloody cars !

Reasonable guesses but not quite right. We tend to use high resolution GC-FID for most of the compositional analysis (MS is a great identification tool but has large variation in response so each...
Forum: The lounge 21st November 2017
Replies: 122
Views: 4,921
Posted By Petrochemist
Re: Bloody cars !

Yes the number of components is typically from fractionation. Back in the 70's neat toluene was apparently used for F1 fuel, regulations have since changed to ensure it's more like road fuel. The...
Forum: The lounge 21st November 2017
Replies: 122
Views: 4,921
Posted By Petrochemist
Re: Bloody cars !

What do you want to know?


Petrol is a much more complex beast than most people think. The US standard describing gasoline (as they call it) runs to over 20 pages IIRC telling how physical...
Forum: General accessories 21st November 2017
Replies: 14
Views: 2,057
Posted By Petrochemist
Re: Waterproof backpack?

A rigid case that's brought to fit the carry on sizes without squashing will be considerably better for your hardware. I wouldn't trust my gear to a bag that had to be squashed into a frame.

...
Forum: General accessories 20th November 2017
Replies: 14
Views: 2,057
Posted By Petrochemist
Re: Waterproof backpack?

I don't think there's any such thing as 100% waterproof. Even deep sea submarines have limits :)


Properly rated hardware would give an ingress protection...
Forum: Foto Fair 16th November 2017
Replies: 5
Views: 395
Posted By Petrochemist
Re: More from E Anglian Life

I definitely need to arrange a visit here!
Showing results 1 to 25 of 70

 
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