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RF Rokkor 500/8 with Lens Turbo 0n NEX-5
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PostPosted: Mon Jul 15, 2013 12:31 pm    Post subject: Reply with quote
Impressive samples, thank you!


PostPosted: Mon Jul 15, 2013 2:10 pm    Post subject: Reply with quote
Attila wrote:
Impressive samples, thank you!


You're welcome !


PostPosted: Mon Jul 15, 2013 4:26 pm    Post subject: Reply with quote
New bokeh monster ? Smile


PostPosted: Mon Jul 15, 2013 5:22 pm    Post subject: Reply with quote
Wow, very good edge detail! Thanks, Ferrick!

sammo wrote:
I still somehow disagree with the last expanation given, which was clear about the focal reducers performance, but not about the understanding of how it works, and think that I made a correct statement. Two things are important to understand the effect of a focal reducer, first, it is irrelevant if it gains a full stop or 2/3 of a stop, I wasn't aware that it was not a full stop gain for this reducer. Second, and most important - the definition of focal ratio stays the same: f ratio = focal lenght / aperture diameter.

Because the aperture diameter did not change it is impossible to say that this lens became a 250mm f/4! You can't put these two values together like that, because it's confusing.


The formula still holds. Do it this way to reduce the confusion. We have a 250mm f/5.6 lens, right? Putting a telecompressor between it and the camera means we will need to multiply the focal length by about 0.72. This gives us 180mm "effective" focal length. At f/4. Using the focal length/aperture/front objective formula: Divide 180 by 4 and we get 45 front objective size. Divide 250 by 5.6 and we get 44.64 front objective size. Round it up and we have 45. They agree with each other. The numbers hold. On a 1.5 crop body, the 180mm focal length will give the appearance of a 180 x 1.5 = 270mm on a full-frame camera. But please recall that the 180mm number is arrived at because of the telecompressor and that it is independent of what a camera "sees." Because of its crop ratio, the 270mm focal length is what the camera "sees" with the 180mm value.

Nobody's saying it is a 270mm f/4, just that it behaves as if it is one because the camera just "sees" the central 66-2/3% of the image. You can't say that the f/stop has decreased (in size, not number) just because the camera only sees the central portion of the image. If you have an evenly lit subject to evaluate, every bit of that subject is receiving the same amount of light as every other bit. So it doesn't matter how much or how little of the subject is included in the image, provided it's all illuminated the same. If you have a full frame and a crop body camera and two lenses of similar focal lengths, this is easy enough to test, as I mentioned in my previous post. Meter something evenly lit, like a blank wall, such that it doesn't matter what focal length either camera's lens is. If your cameras' meters are accurate, they should agree with each other, or at least come close. (Different camera makers have different philosophies as to what constitutes correct exposure, so it's possible to have some variance.)


PostPosted: Mon Jul 15, 2013 6:09 pm    Post subject: Reply with quote
Beautiful lotus shots, Well done !
A focal reducer with a mirror lens was a well-known solution, before the popularity of speed booster/lens turbo
http://discount-photo-import.com/1_objectif_photo.html
(old link)
And it works !
http://discount-photo-import.com/Photos_Rubinar.htm


PostPosted: Mon Jul 15, 2013 9:48 pm    Post subject: Reply with quote
asterinex wrote:
New bokeh monster ? Smile



A 500mm lens should produce nice bokeh due to it's long focal length . Thanks for viewing ! Smile Smile


PostPosted: Mon Jul 15, 2013 9:59 pm    Post subject: Reply with quote
[quote="cooltouch"]Wow, very good edge detail! Thanks, Ferrick!

Thanks, Michael ! Smile Smile


PostPosted: Mon Jul 15, 2013 10:02 pm    Post subject: Reply with quote
Phenix jc wrote:
Beautiful lotus shots, Well done !
A focal reducer with a mirror lens was a well-known solution, before the popularity of speed booster/lens turbo
http://discount-photo-import.com/1_objectif_photo.html
(old link)
And it works !
http://discount-photo-import.com/Photos_Rubinar.htm



Thank you and thanked for the informative link! Smile Smile


PostPosted: Tue Jul 30, 2013 4:12 am    Post subject: Reply with quote
I missed this topic, very nice results. I can't wait for my Rokkor 500/8 to come Very Happy


PostPosted: Tue Jul 30, 2013 6:29 am    Post subject: Reply with quote
IAZA wrote:
I missed this topic, very nice results. I can't wait for my Rokkor 500/8 to come Very Happy


Thank you for viewing ! : )


PostPosted: Tue Jul 30, 2013 9:08 am    Post subject: Reply with quote
Awesome results!
Thanks for sharing. These samples make me want a lens turbo for minolta ... And another one for konica AR...
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