Focal Points..and Issues - Coin Community Forum

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Author	Replies: 5 / Views: 1,555
aladinslamp Pillar of the Community United States 3076 Posts	Posted 11/21/2011 01:42 am Lenses always have some issues of how they can be used..or best be used..Stock lenses allow all the functions of the camera's abillities to be used.. when you change lenses . the main point being is, the focal length for the lens you have,,,where you can get into great focus... this length is often determined by the lens size, though I will say most use the stock lenses,, for instance..and 18MM-55MM lens allows the camera to use its full functions, however if one uses a straight 55MM on your camera....there is a focal distant factor to get the lens to work with the newer cameras....I think there are two focus points using the bellows...the lens attached to the bellows almost fully compressed, gives ultimate zoom macro close ups, and the the extended bellows almost fully extended allows for another focus area...the one is the lens is closest to the camera, and the other is the lens is much farther away from the camera......the result is......the distance of the set up from the objects.... will be different.. So I am wondering if there is some kind of guidlines.. for stock lenses to dedicated to enlarging ring references as far as focusing distances will be...Perhaps its a trial and error thing,but there has been many a comment on the focal plains for lenses...I understand this is not a plug and play thing,, Report this Post to the Staff

SsuperDdave Moderator United States 23522 Posts	Posted 11/21/2011 11:05 am You're thinking it more complicated than it actually is. Mounted directly to the camera, any lens will focus on any object at any distance, up to its' minimum focus distance. With a zoom lens, that minimum focus distance will change during the course of the zoom; that's why you can zoom in on an object and suddenly discover it no longer focuses. The shortest focus distance will be at the lens' widest zoom, and that distance increases as you zoom in. On a bellows, a lens should focus at any extension of the bellows by simply manipulating the distance of the entire apparatus from the coin. It's that simple. Report this Post to the Staff
aladinslamp Pillar of the Community United States 3076 Posts	Posted 11/22/2011 01:46 am Thanks Dave, I was thinking the same thing, but realizing, certain lenses either attached to the camera, or to the bellows have there own unique circumstances depending on how these are being plugged in,, So as not to confuse any one, the same 55MM non stock lens being adapted to the camera and the same lens attached to the bellows, will have different distances of focus...Using the bellows, one can have the lens, with the bellows totally collapsed for one field field of view, and another with the bellows totally extended , my findings are : with the lens closest to the camera will give the most macro of a small point of the entire image,, meaning for the coin, say,, you will only get the date shot, not the full image...with the bellows extended you can get a better macro shot at the full coin, depending on the size of the coin with the lens MM size... AS I am trying for Morgans most likely 75mm minimum to 100/105mm old stock lens is needed...Thanks for your rep[ly Dave... Report this Post to the Staff
rmpsrpms Pillar of the Community United States 4038 Posts	Posted 11/22/2011 4:52 pm Gene...you have it backwards. When the lens is closest to the camera it is the lowest magnification, ie the full coin. When the bellows is extended, it is the highest magnification, ie the date or mintmark shot. The problem with bellows is if the lens is too short, you can't get the lens close enough to the camera to get the whole coin in the image. Longer lenses need to be farther from the camera so are easier to make work at low magnifications. That's why a 105mm may work better than 75mm on bellows for full coin images. Contact me for photographic equipment or visit my home page at: http://macrocoins.com Report this Post to the Staff
aladinslamp Pillar of the Community United States 3076 Posts	Posted 11/22/2011 11:17 pm Thanks guys, I'm re-reading your comments and trying to take them in, as so far the only images I can get into focus are under my topic questioning,,I'm never afraid to revert to square one... Report this Post to the Staff
aladinslamp Pillar of the Community United States 3076 Posts	Posted 11/22/2011 11:43 pm Thanks for your comments,,,,The magnifications is incredibly stupid...and very close to the coin, I see now the need for the Jansco's....how is a 135mm enlarger for Morgans? I assume 105MM is about right...135 to much? Report this Post to the Staff
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