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ffffgdave · Joined: 24 Jun 2005 Posts: 6 Location: montana

thanks for your help.. what happens if i shoot at a focal range of about 30 feet or so.. how much of the negative will be lost due to setting on the front
rails and not being able to lower
the bed?? what happens at 5 feet? thanks dave..

Dan Fromm · Joined: 14 May 2001 Posts: 2146 Location: New Jersey

ffffgdave · Joined: 24 Jun 2005 Posts: 6 Location: montana

im considering buying a wide angle and want to be sure to get the right one Dan. thanks for your help.. focused at infinity i can get about 35mm adjustment out towards the bed with the bed down. i was curois if anyone knew where that aproximate focus range would be at maximum extenstion (35mm) with bed down.. im gessing when i find one for a reasonable price ill know that answer.. i will be using it on 4x5 and 6x9.. dave..

ffffgdave · Joined: 24 Jun 2005 Posts: 6 Location: montana

i just reailzed that is half the distance of the lens and one to one would be 65mm? so what is half of infinity and one to one?? i may have this all wrong..dave..

Les · Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI

Are you asking "What is the focus of a 65mm lens with it racked out 35mm from inf?"

The formula is Object distance S=f*(1+m/m) where m is the magnification.

m=image distance s'-f/f.

In your case the image distance is 65mm+35mm or 100mm. Focal length is 65mm.

m=(100-65/65)=.53

now to the top formula. s=65*(1+.53/.53) or 185mm or 7.3 inches.

(It's more of a challenge when you use a slide rule!) :smile:

[ This Message was edited by: Les on 2005-06-26 22:17 ]

ffffgdave · Joined: 24 Jun 2005 Posts: 6 Location: montana

Less, it looks like your figures seem to be in the correct range.. i took out my crown with a rodenstock 135.. set it at infinity measured it, and put it out to 1.5 times the infinity setting.. about 8 3/4 inches.. i looked thru the glass and it foccuesed at about 12 inches.. this is great! it doesnt look like the 65mm will be giving me any trouble at all on my crown,, thanks to allthat has helped, i can buy a better one, that is used in better condition with not worrying about wasteing the money.. thanks again dave..

perrycas · Joined: 30 Mar 2005 Posts: 48 Location: Sydney Australia

Dave I have a 65mm SA on a 4x5 Crown and at 30ft with the bed dropped its ok. Thats looking through the GG. I also use a 6x12 back with it so i dont have any probs with the bed -I havent even seen the bed with it droppped. Something that gets around the problems with landscape /'scenics' - one get a lot of foreground and sky that one (this one anyway) wants to crop later. My only real problem apart from the distance is that at times its necessary to wiggle the camera about a bit to get everything 'in', and as soon as you move the camera out of the horizontal those verticles start converging, and as the lense is way back there in the camera - no movement. Feel free to send me a mail if you would like to see some examples.
perrycas@optusnet.com.au

ffffgdave · Joined: 24 Jun 2005 Posts: 6 Location: montana

now that i know the 65 will work and you have on on the crown,, how do you find the falloff problems? do you feel you need a center filter... i think you could get some movementif you took the exterior focus wire off from on top of the lens board?? . do you have multicoated? if not does it cause any problems?.. do you have f8, if so do you wish you would have gotten the 5.6. dave..

perrycas · Joined: 30 Mar 2005 Posts: 48 Location: Sydney Australia

I have an F8. It's what i could afford. It has fall off, happy to show you examples. Removing the sports viewer might give you some movement, but not much, and with a lense with this much dof I suspect movement might well have a negative effect. I have had no probs with the coatings, I beleive its a multicoated, its a Linhof select. Actually the fall off can look pretty good at times.
p

Les · Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI

Multi coatings came in the late 70s to mid 80s, I'm not saying they didn't make an SA f8 65mm then, but all the ones I've seen on ebay are from the 50s and 60s. They are fine optics I I bet you'd be hard pressed to see any difference in a typical 4x5 chrome between coated and multi-coated even with a loupe.

Les