Bit of help needed if you please!

[Ash]

Right!

I've decided I need to sort the only other GAS-related problem that I've been avoiding. It's in the research stage.

Here goes!


What are the filter thread sizes for the following lenses?
-Summicron 50/2 collapsible LTM
-Canon 50/1,8 LTM
-CZJ Sonnar 50/2 collapsible Contax mount

Ortho film.
It's insensitive to red, so red is not exposed, which means if I shot a piece of red card will come out black?
I can't get my head around this problem - if I want to get red areas exposed on the film, what combination of filters do I need? This important since it's my only source of 4x5 film, and I won't want to shoot a photo of someone and have them turn out horribly blotchy or something!

Also, I've lost my bookmark to the site I had before:
Is there a website with a low-down of each colour filter and its effect on black and white? ie, red filter darkens blue = dramatic sky etc



I know I know, these are all lazy requests, but I'm tired and I want you lovely people to do my homework for me 😀 😀


Thanks!


(once I've sorted all this, then I can look into filters for the LTM/Contax lenses, and then filters for LF)

 

[rover]

39/40/40.5 for the filters.

 

[Ash]

Thanks rover.. I realised I have a 40.5 step up/down ring from when I had a Jupiter-8. The Contax has a happy-looking dusty 52mm red filter on the front of it now, lol. One down.

That'll do til I track down a 40.5 filter 🙂

 

[Ash]

I got impatient... Found a filter chart here.. http://www.cameracraft.com/filters.htm

 

[FrankS]

Ash, there is no filter or combination of filters you can use to get ortho film to record a red object as anything but dark in a B+W print.

 

[physiognomy]

I know I know, these are all lazy requests, but I'm tired and I want you lovely people to do my homework for me 😀 😀

Good luck getting a set of filters together Ash. I'm doing the same thing myself, but I'm wrestling with whether to get one or two top notch 'must haves' or a better range of cheaper filters. I hate to stick a no-name filter in front of a class lens, but then again I haven't won the lottery lately. 40mm filters for the 50/1.8 have been a little hard to find...

I had a listserv email forwarded to me today from a prof. at another university... He was looking for some micrograph images available in common text books. I nearly wrote back giving him a jpeg map of his campus with directions to the library... 😀 😀 😀 needless to say I didn't.

Peter

 

[Kim Coxon]

The theory of any filter in monochrome is that it will lighten it's own colour and darken those of a different wavelength. So a red filter will darken green and blue and lighten red. Hence it's use to dramatically darken blue skies with Pan film.

Even Pan film is less sensitive to the red end compares with the blue end. (Silver halides are sensitive to blue light, the rest is achieved by adding dyes.) So the sames "rules" wiil apply to Ortho film with one exception. If you used a "true" red filter, you would get a blank photo. According to my bible, Pale yellow will give partial correction for both Ortho and Pan film. A yellow/green will give full correction with Pan but full correction is not possible with Ortho.

Kim

Right!


Ortho film.
It's insensitive to red, so red is not exposed, which means if I shot a piece of red card will come out black?
I can't get my head around this problem - if I want to get red areas exposed on the film, what combination of filters do I need? This important since it's my only source of 4x5 film, and I won't want to shoot a photo of someone and have them turn out horribly blotchy or something!

Also, I've lost my bookmark to the site I had before:
Is there a website with a low-down of each colour filter and its effect on black and white? ie, red filter darkens blue = dramatic sky etc



Thanks!


(once I've sorted all this, then I can look into filters for the LTM/Contax lenses, and then filters for LF)

 

[Kim Coxon]

That chart is good for Pan film but is not fully accurate for Ortho. 😉

Kim

I got impatient... Found a filter chart here.. http://www.cameracraft.com/filters.htm

 

[FrankS]

It could be an interesting effect: ortho film for portraits. Try it and see what happens.

 

[Ash]

So I'm best looking for the most lime-coloured filter I can find, if I am to pull anything from the lost tonal range?

This thread on peanut left me at a loss http://photo.net/bboard/q-and-a-fetch-msg?msg_id=00J3gO but it helped me get my head around, and understand that red doesnt exist for ortho. I was hoping that there was still a way to pull the tones out.

As for filters, I've no problem using no-name cheap filters, as long as it isn't scratched to hell or obviously rubbish.


Now.... to find a willing subject to sit still while I set up the Cambo and try and take a photo of them!

 

[Kim Coxon]

Hi Ash,
As I said before, basic silver halide crystals are only sensitive to blue light. In 1873, Vogel discovered that by adding a dye to the plate, the film would also be sensitive to green light. The dye used is usually erythrosin. Around the turn of the century, extra dyes started to be added on a commercial basis to extend the spectral range to to aroound 660-670 nm. This fairly closely matches the sensitivity of the eye and gave rise to Pan films. From the 30's this was gradually extended to 1200 nm which is where the IR films come in.

Ortho film is sensitive to light in the 350-580 nm range. Outside of this, it will not record an image regardless of filtration. Within this range the highest peak would be in the blue range using daylight hence the need for a pale yellow filter. Under tungsten light the peaks shift and it the highest peak is in the green area though not very pronounced. If you are intending to do portraits under artificial light, I would forego the filter.

Kim

 

[Ash]

Right. I think I got that now. Blood and stone 😉

I'll have to experiment then. I'm tempted to place a large filter over a studio light (or something) so the subject would become, say, light green. Would that bring everything in the spectrum down a few nm?

If the subject is awash with light from the spectrum that ortho will pick up, then maybe the red tones will then be visible? Not as red tones, but as tones under artificial lighting.

((In the same vein as 2 apples - a red apple or a green apple. Identical tonal range but one is red, one is green. The ortho can pick up the tones on the green apple happily, but the red won't expose, so could trick lighting makes the red apple look green?))


With all that said, I'm more likely to try this in natural lighting, or just try it out with no filters and see how I go!

 

[Xmas]

Ash

The ortho will wash out sky and distant hills of Wilts. yellow will pull some detail out...

I'll send you a 52mm hood next, if I have one to hand.

Noel

 

[Ash]

Thanks noel 🙂

 

[oscroft]

The theory of any filter in monochrome is that it will lighten it's own colour and darken those of a different wavelength

Well, technically, it doesn't actually lighten anything - it just darkens its own colour less than the others, and a corresponding increase in exposure does the lightening.

But yes, I agree - there is no filtering that will add a specific colour sensitivity to a film that doesn't have it.

 

[markinlondon]

If you're looking for odd stepping rings, Ash, these guys can make you just about anything.

www.srbfilm.co.uk/

 

[Ash]

I'll look into them, what is the quality-vs-price ratio like?

 

[Kim Coxon]

SRB quality is very good but they are not cheap. Have you looked at using a series system? They can be picked up very cheaply and once you have the adapters, one size fits most!. 😀

Kim

I'll look into them, what is the quality-vs-price ratio like?

 

[Ash]

I was hoping to get away with something like the Actina filters I have for the Zeiss Nettar... one filter holder, which attaches to the lens.

Retaining ring unscrews, filter pops out, new filter goes in, retaining ring back on - interchangeable filters. It'll probably end up costing more to source that kind thing for each camera, unless I can find filter glass that will fit the 3 lenses and................thats too much effort. I'll look into a couple screw-in 39, 40, and 40.5 filters. Save up and buy each colour when I can

 

[Xmas]

Ash

Don't try red on landscapes...

Noel

P.S. Vintage Camera Ltd have filters, hoods, series rings, and step ring 2nd user, but still not cheap your playmates in Swindon are best bet.