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RF Rokkor 500/8 with Lens Turbo 0n NEX-5
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PostPosted: Sun Jul 14, 2013 2:00 pm    Post subject: RF Rokkor 500/8 with Lens Turbo 0n NEX-5 Reply with quote
Purchased this Lens Turbo (Chinese made) this afternoon. Put it on my NEX-5 and then used my RF Rokkor 500/8 to shoot lotus handheld. Since the Lens Turbo intensify the light, f-stop enhanced by something like one f-stop. Handheld is now not a problem with this lens! Very Happy Very Happy



















PostPosted: Sun Jul 14, 2013 2:06 pm    Post subject: Re: RF Rokkor 500/8 with Lens Turbo 0n NEX-5 Reply with quote
[quote="ferrick"]Purchased this Lens Turbo (Chinese made) this afternoon. Put it on my NEX-5 and then used my RF Rokkor 500/8 to shoot lotus handheld. Since the Lens Turbo intensify the light, f-stop enhanced by something like one f-stop. Handheld is now not a problem with this lens! Very Happy Very Happy

More!















PostPosted: Sun Jul 14, 2013 2:14 pm    Post subject: Reply with quote
the lotus shots are really impressive !


PostPosted: Sun Jul 14, 2013 2:18 pm    Post subject: Reply with quote
tomzcafe wrote:
the lotus shots are really impressive !


Thank you! The shots were taken in mid-day. Next time should go either in the morning or late afternoon. The light conditions would be better then! Sad Sad


PostPosted: Sun Jul 14, 2013 2:27 pm    Post subject: Reply with quote
First, well done, photographer!!!

Second, i lile the lens. It's in my list now.


PostPosted: Sun Jul 14, 2013 2:31 pm    Post subject: Reply with quote
DR.JUAN wrote:
First, well done, photographer!!!

Second, i lile the lens. It's in my list now.


Thanks for your appreciation! Smile Smile


PostPosted: Sun Jul 14, 2013 2:51 pm    Post subject: Reply with quote
Beautiful stunning images. The Speedbooster really could bring back life to the Mirror lenses by making them faster.

I would love to see how the Rokkor 250/5.6 does on a NEX with the speedbooster. A full frame equivalent of 180/4 small as a 50mm lens Smile


PostPosted: Sun Jul 14, 2013 3:12 pm    Post subject: Reply with quote
Pontus wrote:
Beautiful stunning images. The Speedbooster really could bring back life to the Mirror lenses by making them faster.

I would love to see how the Rokkor 250/5.6 does on a NEX with the speedbooster. A full frame equivalent of 180/4 small as a 50mm lens Smile


RF Rokkor 250/5.6 is my dream lens too! However, it's way too expensive nowadays and I can't afford it! Crying or Very sad Crying or Very sad


PostPosted: Sun Jul 14, 2013 3:12 pm    Post subject: Reply with quote
Pontus wrote:
Beautiful stunning images. The Speedbooster really could bring back life to the Mirror lenses by making them faster.

I would love to see how the Rokkor 250/5.6 does on a NEX with the speedbooster. A full frame equivalent of 180/4 small as a 50mm lens Smile


RF Rokkor 250/5.6 is my dream lens too! However, it's way too expensive nowadays and I can't afford it! Crying or Very sad Crying or Very sad


PostPosted: Sun Jul 14, 2013 5:57 pm    Post subject: Reply with quote
tomzcafe wrote:
the lotus shots are really impressive !
+1


PostPosted: Sun Jul 14, 2013 6:08 pm    Post subject: Reply with quote
Great use of the lens. Thumbs up.


PostPosted: Sun Jul 14, 2013 7:08 pm    Post subject: Reply with quote
Great images!

Pontus wrote:

I would love to see how the Rokkor 250/5.6 does on a NEX with the speedbooster. A full frame equivalent of 180/4 small as a 50mm lens Smile


That's incorrect. The 35mm equivalent of the speedboosted crop camera is more or less what the lens does on a 35mm camera. Effectively there is no smaller dof and no better light gathering ability! It is stil the same lens Smile
A croped 180/4 lens would make the same image...if it would exist Wink


PostPosted: Sun Jul 14, 2013 8:03 pm    Post subject: Reply with quote
sammo wrote:
Great images!

Pontus wrote:

I would love to see how the Rokkor 250/5.6 does on a NEX with the speedbooster. A full frame equivalent of 180/4 small as a 50mm lens Smile


That's incorrect. The 35mm equivalent of the speedboosted crop camera is more or less what the lens does on a 35mm camera. Effectively there is no smaller dof and no better light gathering ability! It is stil the same lens Smile
A croped 180/4 lens would make the same image...if it would exist Wink


But you are yourself saying that the f5.6 lens would become a f4 lens. I think we are both getting confused, we write what we don't mean.

Yes. I'm of course wrong in thinking that the lens would become a 180mm lens. It becomes a 0.71x250x1.5 equivalent lens which is 266mm. According to Metabones the speed will increase by one stop. A 266mm/f4 lens FF equivalent then.


PostPosted: Sun Jul 14, 2013 8:10 pm    Post subject: Reply with quote
The flowers looks really nice Wink

Cool to see shoot with lens turbo, speed booster etc., thx!


PostPosted: Sun Jul 14, 2013 9:16 pm    Post subject: Reply with quote
sammo wrote:
Great images!

Pontus wrote:

I would love to see how the Rokkor 250/5.6 does on a NEX with the speedbooster. A full frame equivalent of 180/4 small as a 50mm lens Smile


That's incorrect. The 35mm equivalent of the speedboosted crop camera is more or less what the lens does on a 35mm camera. Effectively there is no smaller dof and no better light gathering ability! It is stil the same lens Smile
A croped 180/4 lens would make the same image...if it would exist Wink


Actually this isn't quite true, according to an evaluation of the Lens Turbo over at the Pentax forums. A fellow there who tested it said that he was getting up to 2/3 stop more light -- not a full stop. You can read his evaluation here:

http://www.pentaxforums.com/forums/pentax-slr-lens-discussion/228831-evaluating-lens-turbo.html

Theoretically, your basic telecompressor or focal reducer of this type, call it whatever you want, reduces image size by a factor of about 0.72 and increases the light gathering ability by one stop. Whether metabones Speed Booster, Zhongyi/Mitakon Lens Turbo, or Fotodiox Vizelex, they all work off the same principle. This guy was pointing out that, with his Pentax setup, he wasn't seeing a full stop increase, instead from 1/3 to 2/3 of a stop. So, realistically then, on a 1.5x crop camera, a 250/5.6 behaves as if it were a 375mm f/5.6 on a 35mm and with the focal reducer, theoretically, it should behave as the equivalent of a 270mm f/4. (0.72 x 375 = 270), but it's more likely to behave as a 270mm f/4.5 in terms of light gathering only. Depth of field is affected rather subtly, and I'd recommend you read the article to find out more.

I've read where some people claim that there is a reduction in light when, say, a 200mm f/4 is mounted to a crop body camera, such that it becomes like a 200/5 or 200/5.6. I've never understood why this should be so, and I've never seen that with my outfit. In fact, I just confirmed it. I took some light readings with my EOS DSLR and a 70-210mm f/4 EF lens and my Canon F-1 with an FD 70-210mm f/4 attached. Because the two zooms are effectively different focal ranges on the two cameras, I selected a variety of evenly lit subjects to take the specific focal lengths out of the equation, then metered them so I could get an average of sorts, but it wasn't really necessary. The two cameras were consistently showing the same, or almost the same, values. Both cameras were set to ISO 100 and both were using partial metering pattern. I was also taking some sample shots with my DSLR and evaluating the histograms to make sure it was exposing accurately. The histogram curves were right in the middle, right where I want to see them.

So real-world tests would seem to indicate a small, but noticeable bias toward the acceptable field of focus to be somewhat forward of the subject, instead of the field being split evenly front and rear, and a noticeable improvement in light gathering ability. To me, this represents a real boon for folks who use fast glass. A 55mm f/1.2 or 85mm f/1.2 will be getting really close to being f/1.0 optics. And, while the field depth will not be greater, since it is biased toward the front of the subject, there's a greater likelihood of best focus being achieved.

Oh and by the way, Ferrick! Those are some beautiful shots of the lotus flowers!


PostPosted: Sun Jul 14, 2013 11:11 pm    Post subject: Reply with quote
SonicScot wrote:
tomzcafe wrote:
the lotus shots are really impressive !
+1


Thank you! Smile Smile


PostPosted: Sun Jul 14, 2013 11:14 pm    Post subject: Reply with quote
Bille wrote:
Great use of the lens. Thumbs up.


Thanks for viewing ! Smile Smile


PostPosted: Sun Jul 14, 2013 11:15 pm    Post subject: Reply with quote
sammo wrote:
Great images!


Thanks for viewing ! Smile Smile

Pontus wrote:

I would love to see how the Rokkor 250/5.6 does on a NEX with the speedbooster. A full frame equivalent of 180/4 small as a 50mm lens Smile


That's incorrect. The 35mm equivalent of the speedboosted crop camera is more or less what the lens does on a 35mm camera. Effectively there is no smaller dof and no better light gathering ability! It is stil the same lens Smile
A croped 180/4 lens would make the same image...if it would exist Wink


PostPosted: Sun Jul 14, 2013 11:17 pm    Post subject: Reply with quote
Nordentro wrote:
The flowers looks really nice Wink

Cool to see shoot with lens turbo, speed booster etc., thx!


Thanks! Smile Smile


PostPosted: Sun Jul 14, 2013 11:24 pm    Post subject: Reply with quote
cooltouch wrote:
sammo wrote:
Great images!

Pontus wrote:

I would love to see how the Rokkor 250/5.6 does on a NEX with the speedbooster. A full frame equivalent of 180/4 small as a 50mm lens Smile


That's incorrect. The 35mm equivalent of the speedboosted crop camera is more or less what the lens does on a 35mm camera. Effectively there is no smaller dof and no better light gathering ability! It is stil the same lens Smile
A croped 180/4 lens would make the same image...if it would exist Wink


Actually this isn't quite true, according to an evaluation of the Lens Turbo over at the Pentax forums. A fellow there who tested it said that he was getting up to 2/3 stop more light -- not a full stop. You can read his evaluation here:

http://www.pentaxforums.com/forums/pentax-slr-lens-discussion/228831-evaluating-lens-turbo.html

Theoretically, your basic telecompressor or focal reducer of this type, call it whatever you want, reduces image size by a factor of about 0.72 and increases the light gathering ability by one stop. Whether metabones Speed Booster, Zhongyi/Mitakon Lens Turbo, or Fotodiox Vizelex, they all work off the same principle. This guy was pointing out that, with his Pentax setup, he wasn't seeing a full stop increase, instead from 1/3 to 2/3 of a stop. So, realistically then, on a 1.5x crop camera, a 250/5.6 behaves as if it were a 375mm f/5.6 on a 35mm and with the focal reducer, theoretically, it should behave as the equivalent of a 270mm f/4. (0.72 x 375 = 270), but it's more likely to behave as a 270mm f/4.5 in terms of light gathering only. Depth of field is affected rather subtly, and I'd recommend you read the article to find out more.

I've read where some people claim that there is a reduction in light when, say, a 200mm f/4 is mounted to a crop body camera, such that it becomes like a 200/5 or 200/5.6. I've never understood why this should be so, and I've never seen that with my outfit. In fact, I just confirmed it. I took some light readings with my EOS DSLR and a 70-210mm f/4 EF lens and my Canon F-1 with an FD 70-210mm f/4 attached. Because the two zooms are effectively different focal ranges on the two cameras, I selected a variety of evenly lit subjects to take the specific focal lengths out of the equation, then metered them so I could get an average of sorts, but it wasn't really necessary. The two cameras were consistently showing the same, or almost the same, values. Both cameras were set to ISO 100 and both were using partial metering pattern. I was also taking some sample shots with my DSLR and evaluating the histograms to make sure it was exposing accurately. The histogram curves were right in the middle, right where I want to see them.

So real-world tests would seem to indicate a small, but noticeable bias toward the acceptable field of focus to be somewhat forward of the subject, instead of the field being split evenly front and rear, and a noticeable improvement in light gathering ability. To me, this represents a real boon for folks who use fast glass. A 55mm f/1.2 or 85mm f/1.2 will be getting really close to being f/1.0 optics. And, while the field depth will not be greater, since it is biased toward the front of the subject, there's a greater likelihood of best focus being achieved.

Oh and by the way, Ferrick! Those are some beautiful shots of the lotus flowers!


Thanks Michael for the detailed explanation. Smile Smile


PostPosted: Mon Jul 15, 2013 1:06 am    Post subject: Reply with quote
ferrick wrote:
Thanks Michael for the detailed explanation. Smile Smile


Not a problem. I've been fascinated with these things ever since I first heard of one. You know, in astronomy, the idea of a telecompressor is nothing new. They've been around for decades, and are quite useful for turning a scope with a rather tight field of view into a wide field scope. Giving it a boost in light is also helpful for astrophotography. I've often wondered why telecompressors weren't made for cameras, but it hadn't ever occurred to me that they would be useful in restoring the wideness to wide-angle lenses until I read about the Speed Booster.

I'm still waiting for a camera maker to release a FF MILC, mostly so I can use my 35mm wides the way they were intended, but with something like the Speed Booster or Lens Turbo, I don't need to wait anymore. Well, I'm still gonna wait at least until the update of the NEX 7 is released. But if nobody's come out with an FF MILC by that time, I'll just buy the update instead.

BTW, one of the things I appreciate about your photos is, with several of them, you're showing detail out toward the edges. So this adapter looks like it's holding edge detail pretty well. I would be most curious to see a center/corner sharpness comparison, though. Feel up to it?


PostPosted: Mon Jul 15, 2013 8:33 am    Post subject: Reply with quote
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. Let's say that the gain is indeed one stop, to make it easier to understand: You can either say that you have a 250mm 35mm equivalent focal length with f/4 aperture, or you can say that you have a 180mm f/4 lens on a crop camera (which is basically the same thing). But the ideal behaviour of the lens (DOF and light gathering abilities) would be like the 250mm f/5.6 lens on a full frame, because you are on a cropped camera with a focal reducer.
It is well known that a larger format camera get's always a smaller DOF at the same aperture and composition setting than a cropped camera, right? So to have the view of the 35mm on a crop camera, the aperture needs to be lower and this is what we see here.

And it's the same with the light gathering ability, on a crop camera some light that the lens gathered is being wasted. Because a 35mm has about twice the surface area than a crop, the difference is about 1 stop. This effect is seen more or less only on high ISO performace, full frame cameras with the same detector technology were always a step better than their crop counterparts. If with this focal reducer better ISO performance on a crop than on a full frame is observed, it means that the smaller sensor is more light sensitive than the larger.
The same principle we use in astronomy, because the small sensors were so much more sensitive then the large ones (and loads cheaper) it makes sense that the focal lenght is reduced and optimised for a small sensor, rather then to put a large sensor on the telescope, even if the field of view gathered is the same and accualy some light is lost on the focal reducer. But again, if the non-focal reduced sensor in sensitive as a small sensor it doesn't make sense to do this (that's why focal reducers are used only by amateurs with limited budged - or for huge telescopea that produce image area far larger than any existing detector).


PostPosted: Mon Jul 15, 2013 8:35 am    Post subject: Reply with quote
Very well done shots, beautiful Lotus flowers indeed!


PostPosted: Mon Jul 15, 2013 11:54 am    Post subject: Reply with quote
cooltouch wrote:
ferrick wrote:
Thanks Michael for the detailed explanation. Smile Smile


Not a problem. I've been fascinated with these things ever since I first heard of one. You know, in astronomy, the idea of a telecompressor is nothing new. They've been around for decades, and are quite useful for turning a scope with a rather tight field of view into a wide field scope. Giving it a boost in light is also helpful for astrophotography. I've often wondered why telecompressors weren't made for cameras, but it hadn't ever occurred to me that they would be useful in restoring the wideness to wide-angle lenses until I read about the Speed Booster.

I'm still waiting for a camera maker to release a FF MILC, mostly so I can use my 35mm wides the way they were intended, but with something like the Speed Booster or Lens Turbo, I don't need to wait anymore. Well, I'm still gonna wait at least until the update of the NEX 7 is released. But if nobody's come out with an FF MILC by that time, I'll just buy the update instead.

BTW, one of the things I appreciate about your photos is, with several of them, you're showing detail out toward the edges. So this adapter looks like it's holding edge detail pretty well. I would be most curious to see a center/corner sharpness comparison, though. Feel up to it?


I used my Minolta 35-70mm f/3.5 and the Lens Turbo to test a few shots today. The pictures below show full pictures as well as center and corner crops. It seems the images at the corners are still tight! Smile Smile


























PostPosted: Mon Jul 15, 2013 11:56 am    Post subject: Reply with quote
kds315* wrote:
Very well done shots, beautiful Lotus flowers indeed!


Thank you for your appreciation! Smile Smile
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