Macro question for Rollei 6008

[david_simonds1]

<p>Friends, I have a 6008i with the Schneider 90mm macro that gets me to 1:2. What would I need to get to 1:1?<br>

Thanks,<br>

David</p>

[q.g._de_bakker]

45 mm of extra extension.

[david_simonds1]

<p>Much obliged for the quick reply.<br>

Does that very modest extension essentially halve the minimum focusing distance (from appx 16" to 8") to create the 1:1 ratio? Any issues using that piece with the 90mm? I ask because I know there are issues using the tele extension given the design of the 90mm.<br>

Thanks<br>

David</p>

[tak_l_jasper_poon]

<p>Dear David,<br>

QG's answer of 45 mm is wrong.<br>

i have personal experience using this lens. in fact if you search this site, i have a very detailed table on the field, magnification and exposure compensation.<br>

tele extension is not extension tube. tele converter cannot get you to 1:1 and 1.4x longar cannot be used with this lens because the back elements is protruding too much and will damage the Longar.<br>

however, there is no problem with extension tubes or bellow extensions. as long as 6000 system tube is used. when older versions are used, you would lose the stop down function. but still the lens can be used.<br>

to go to 1:1 magnification ration, the image distance = object distance = 2x focal length.<br>

that means you need 90mm x 2 = 180mm of image distance.<br>

given that the lens to film distance at infinity is already 90mm, you need an extra 90mm to get to 1:1.<br>

the lens' own helical extension gives you about 25mm of extension. therefore you need a 67mm extension tube. you then set the focusing scale to 500mm. that would give you 1:1.<br>

the exposure compensation will be 2 whole stops.<br>

the image distance is slightly less than 180mm from the lens, but not from the filter rim, because the lens sits in a recess inside this rim.<br>

cheers,<br>

Tak</p>

[tak_l_jasper_poon]

<p>please also see this thread:<br>

<a href="00Wb93">http://www.photo.net/medium-format-photography-forum/00Wb93</a></p>

 

[q.g._de_bakker]

Tak,<br><br>I'm not wrong. I'll explain.<br><br>To be able to focus on infinity, the lens needs to be at a distance in front of the film equal to the focal length. That distance is already provided by camera and lens mount. You cannot put the lens any closer to the film.<br><br>To focus on anything closer, the lens needs to be moved away from the film. The extra distance (extension - you extend the distance between lens and film) needed to get to 1:2 is equal to 1:2 the focal length - 45 mm. (I don;t know where you got that figure, Tak, but 25 mm of extension will not put the lens at 1:2)<br>The lens apparantly already provides that much in the focusing mount, so nothing needed so far.<br><br>To achieve an 1:1 scale, you need extension equal to 1:1 the focal length, i.e. 90 mm.<br>Given that the lens already manages to get at 1:2 (45 mm), only (!) 45 mm of extra extension is needed.<br><br>Spot on, i was. Absolutely right. ;-)<br>And you agree: 90 mm for infinity, 45 mm extension already provided by the lens, 45 mm extra to get to 1:1 = 180 mm. Where you went wrong is that you ignored the fact that 135 mm of all that is already available.

[q.g._de_bakker]

David,<br><br>It does not halve the focusing distance, no.<br>The relation between image and subject distances is given by the 'lens formula': 1/focal length = 1/image distace + 1/subject distance. The focusing distance is the sum of the image and subject distances.<br><br>The relation between scale and image distance is simpler: for every 'whole step' in magnification, you need to increase the image distance by the focal length of the lens. Using a 90 mm lens, 1:1 needs 1x 90 mm, 2:1 needs 2x 90 mm, 1:3 needs 0.333x 90 mm, etc.<br><br>However (there's always something that spoils what other wise is very easy to grasp and use): if the lens employs internal focusing, i.e. changes focal length to focus, the focal length is variable, only equal to the nominal focal length when the lens mount itself is set to infinity focus.<br><br>If that 90 mm lens does indeed use internal focusing, it could be possible that it only needs 25 mm of extension to get at 1:2.<br>It then apparently has a focal length of only 50 mm. And then you only need 25 mm more, and Tak's 65 mm takes you well beyond 1:1.

[david_simonds1]

<p>Gentlemen, I apreciate your kind replies and your technical discussion that will take me a bit of time to digest. Getting to 67mm is easy since there is a Rollei tube of that length. But to get to 45mm is not. I looked a the BH site which identifies 9mm, 17mm and 34mm tubes. Apparently, I can not get precisely to 45mm. Under the circumstances, perhaps it would be best to go with the 67mm tube and then just adjust the subject to lens distance to get to 1:1, if that is right for the composition. I realize the downside of this is the added exposure factor. Would the Rollei bellows rig (a small fortune) resolve this issue? I am not committed to the 1:1 ratio as an absolute. I just want to be able to increase the images size to avoid cropping and enlarging and I have used the 1:1 as a benchmark.<br>

Thanks again.<br>

David</p>

[bengt1664878721]

<p>Might not your goal be achieved with the retro-adapter, maybe in combination with a tube? I know I can get 1:1 with the 80mm Planar retromounted on my SL66.</p>

[tak_l_jasper_poon]

<p>Dear David, i have this lens with me at this moment and i am playing with it. it really takes 67mm extension tube plus adjusting the focusing ring to 500mm (= helical extension of around 20mm) to get to 1:1. (= a total extension of around 90mm)</p>

<p>the bellows unit can surely be used. but since the shortest extension when all the bellows are compressed is exactly 67mm, you would not have the field from 75mm to 140mm. for this range of field you need the 34mm extension tube. the bellows can give you extension from 67mm to slightly over 200mm.</p>

<p>even if you can find a 45mm extension tube (which does not exist for Rollei) you need 45mm extension from the helical extension part of the lens. this is not possible.</p>

<p>indeed, the lens does not really get you down to 1:2 without extension tubes. 1:2 magnification is most easily provided using a 34mm extension tube and setting the focusing distance at around 1000mm.</p>

<p>the best companions for this lens are one 34mm and one 67mm extension tubes. that will give you continual variation of magnification from 1:infinity to around 1:0.7 (stacking both tubes together).</p>

<p>you may refer to my thread mentioned above to get all the intermediate steps of adjustment.</p>

<p>Cheers,</p>

<p>Tak</p>

 

[geoffrey goldberg]

<p>There is a very complete Rollei macro booklet, outlining all the options and lenses in rather remarkable detail. Send me an address and I'll email it to you. </p>

 

[geoffrey goldberg]

<p>too big to upload. </p>

[tak_l_jasper_poon]

<p>Hi, Geoff, many thanks indeed, it is very useful. I wonder if DHW has any plans to produce an updated manual for the new instruments. Tak.</p>

[richard_lehun]

<p>Hi, <br>

The macro booklet is still online, so if those interested send me an email address I can add them.</p>