Sorry, do have a log-in, was just having problems with my AOL browser!
I have a Nizo 801 macro and am very keen to shoot using some of Super8 sound's higher speed films. I have worked out the shutter size of my camera using the formulas provided on Michael Nyberg's site, but the Nizo manual still advises against using external meters because they do not take account of:
1) "the varying focal lengths of the zoom lens"
2) "the light absorbed by the various elements of the zoom lens"
3) "the camera viewfinder prism"
Does anyone know how to work out these figures? Has anyone already worked it out for the Nizo 801 macro and if so does it stay (more or less) the same for every camera?
I have tried looking in the Ilford manual of photography, but the formulas in there on lens speed are like Greek to me!
Hope someone can help.
Best wishes
Daniel
External light meter
Moderator: Andreas Wideroe
Replying to myself
Read the Ilford manual of photography again and am now even more confused!
Apparently the effective aperture varies according to the focal length of the zoom lens. The 'true' aperture can be found with the formula:
(marked f-stop x focal length setting) / the longest possible focal length
But this gives some very odd figures...
Still no closer on the the light lost through the elements in the lens or the viewfinder. Have read the previous postings on the subject, but the methods described seem a bit hit and miss....
Apparently the effective aperture varies according to the focal length of the zoom lens. The 'true' aperture can be found with the formula:
(marked f-stop x focal length setting) / the longest possible focal length
But this gives some very odd figures...
Still no closer on the the light lost through the elements in the lens or the viewfinder. Have read the previous postings on the subject, but the methods described seem a bit hit and miss....
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Old Uncle Barry
- Posts: 645
- Joined: Wed May 01, 2002 11:23 am
- Location: Midlands,UK
](*,) What tripe! For more years than I wish to remember I,and thousands of others have used both on-board and external metering all to good effect.
With external metering use the incident light method and you will get good uniform exposure on general subjects.
For more critical analysis of your subject use the reflected light method as you may be shooting varying areas of light and dark wereupon you take the 'average' reading.
Failing that,use the standard grey card method and take a reflected light readinbg off that.
Manuals are written to confuse.
With external metering use the incident light method and you will get good uniform exposure on general subjects.
For more critical analysis of your subject use the reflected light method as you may be shooting varying areas of light and dark wereupon you take the 'average' reading.
Failing that,use the standard grey card method and take a reflected light readinbg off that.
Manuals are written to confuse.
Re: External light meter
Do you know that Ilford manual? Okdantheman wrote:Sorry, do have a log-in, was just having problems with my AOL browser!
I have a Nizo 801 macro and am very keen to shoot using some of Super8 sound's higher speed films. I have worked out the shutter size of my camera using the formulas provided on Michael Nyberg's site, but the Nizo manual still advises against using external meters because they do not take account of:
1) "the varying focal lengths of the zoom lens"
2) "the light absorbed by the various elements of the zoom lens"
3) "the camera viewfinder prism"
Does anyone know how to work out these figures? Has anyone already worked it out for the Nizo 801 macro and if so does it stay (more or less) the same for every camera?
I have tried looking in the Ilford manual of photography, but the formulas in there on lens speed are like Greek to me!
Hope someone can help.
Best wishes
Daniel
Throw it away along with that Nizo silly manual. Or keep it for reference on a book shelf. Get you camera along with an external light meter. Shoot a cartridge or two using camera readings and external light meter. Keep records of what you did. Process film and observe the differences. Whoever said that you can not use an external light meter is out of his mind. For this, you do not consult manuals - you shoot and compare.
Lunar07
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Lucas Lightfeat
- Posts: 716
- Joined: Tue Dec 03, 2002 1:09 am
- Location: London, England
That trial and error method is all very well and good - and it will lead you to realise that...
...some light is lost in the lens
...some light is lost in the prism
...the 220 degree shutter angle on XL cameras compensates for the prism
...none of it is very critical if you are underexposing anyway, and have a rough (or even better a very good) idea of what the f stop difference between the camera's light meter pointed at a grey card and the incident meter readings.
I agree with Lunar - forget the technical stuff and do some experiments (or use the camera meter as a spot meter as I do, with good results)
Lucas
...some light is lost in the lens
...some light is lost in the prism
...the 220 degree shutter angle on XL cameras compensates for the prism
...none of it is very critical if you are underexposing anyway, and have a rough (or even better a very good) idea of what the f stop difference between the camera's light meter pointed at a grey card and the incident meter readings.
I agree with Lunar - forget the technical stuff and do some experiments (or use the camera meter as a spot meter as I do, with good results)
Lucas
A grey card is your friend. Put a grey card in a well lit location, point your camera at the grey card so that it fills the frame. Then you take a reading with your lightmeter and play with the shutter speed until the fstop readings are the same (or very close). Make sure you set your meter to the same asa that the camera thinks the film is (this is not necessarily what the film actually is). Then shoot a test roll using your shutter speed setting.
Does your cameras manual actually say that the fstop changes as you zoom? if it does and it is right that sucks. Still camera zoom's and many video cameras act this way, but most cine lenses don't as far as I know.
~Jess
Does your cameras manual actually say that the fstop changes as you zoom? if it does and it is right that sucks. Still camera zoom's and many video cameras act this way, but most cine lenses don't as far as I know.
~Jess
I don’t have a background in photography, and have only ever used the internal light meter, so go easy one me; but what exactly is the difference between incidence and reflective light readings?
If I am experimenting with the grey card (to discover exactly how much difference the prism and the lens elements make) should I vary the shutter speed setting until internal and external f-stop readings match?
cheers everyone
Daniel
If I am experimenting with the grey card (to discover exactly how much difference the prism and the lens elements make) should I vary the shutter speed setting until internal and external f-stop readings match?
cheers everyone
Daniel