f-stop sweet spot for 35mm adapter rigs question?

B

Baddgsx

Well-known member
hi friends,

im currently using an sgblade mated to a canon xh-a1 and use nikkon ai-s lenses. i record at 24p with a shutter speed at 1:48.

Is there a formula for calculating the sweet spot for f-stop to no run into sharpness or blurr problems? should the canon f-stop be wider open to compensate lightloss and just use the f-stop on the nikon lenses?

any help on this is much appreciated,
Thanks,
Chris
 
Chris,
There is nothing like testing your own lenses to see how they perform.
In theory both the Canon and the Nikon's will perform best at least a stop down from fully wide open.
But without testing you can't tell which is more critical on your particular set-up.
If your nikon's are 1.4 lenses, they probably suck at 1.4 no matter what, but because your Canon is probably not that sharp you may not see it.

The SG will have a tendancy to focus in the center better than the corners, but how much loss will depend on your set-up. When used with an EX-1 I was comfortable shooting my video camera wide open, because the optics matched the camera well. Also depending on the screen (RR) you use for the SGBLade it may start showing static grain if you stop down past 2.8. Best thing you can do is download a focus chart from the web. Blow it up at Kinko's to 3 or 4 feet , mount on a card and test away with a good monitor.
I posted a chart for this purpose:

http://www.leonardlevy.net/ISO_12233-reschart.pdf
 
I am also using an SGblade. I get the best image out of my old Nikons by using them at f5.6, and trying to keep the camera as close to and if possible at f5.6 too. Achieving this is possible thanks to ND filters that my camera has built in.

My opinion is purely a guideline, test for yourself. Sometimes I find that F2.8 can be really nice, or around F8. But this depends also on what ROTOrazor you use. I use RR1 and that makes the F stop choices flexible as hell, because you can go down all the way to F16 without the grain showing up.

If you want the sharpest and best looking "blurriness" (bokah) get the RR1. The RR2 gives you "more" bokah but also a softer image that can be pretty frustrating as it always seems to be out of focus. Not to meniton the F stop limitations. RR1 has a bit "less" bokah, but belive me, there's still plenty to go around.
 
Admir said:
I am also using an SGblade. I get the best image out of my old Nikons by using them at f5.6, and trying to keep the camera as close to and if possible at f5.6 too. Achieving this is possible thanks to ND filters that my camera has built in.

My opinion is purely a guideline, test for yourself. Sometimes I find that F2.8 can be really nice, or around F8. But this depends also on what ROTOrazor you use. I use RR1 and that makes the F stop choices flexible as hell, because you can go down all the way to F16 without the grain showing up.

If you want the sharpest and best looking "blurriness" (bokah) get the RR1. The RR2 gives you "more" bokah but also a softer image that can be pretty frustrating as it always seems to be out of focus. Not to meniton the F stop limitations. RR1 has a bit "less" bokah, but belive me, there's still plenty to go around.
Click to expand...


I have the RR2 installed. Im going to switch it tonight to RR1. How much sharper is RR1 than RR2? maybe switching to RR1 will help with the sharpness issue im facing.

Thanks for the advice.

Chris
 
I also started out with the RR2. But I got really frustrated with the ammount of bokeh and the soft image. My HMC is a somewhat "soft image" camera to begin with. Many times I wanted to go below F5.6, and doing that with the RR2 was not possible without picking up the grain.

The RR1 is definitly sharper, and has a bit less light loss too, but nothing drastic. The bokeh is definitly more pleasing to me, and reminds a lot of the Letus look you get.

I wouldn't use the RR3. Sure it has less light loss, and almost non additional bokeh compared to the oter Rotorazors. But it has some really bad vignetting going on, that is due to the really thin glass it's made of. It's just not worth it IMO.
I don't know if you have the flip unit, but the flip gives you a bit less edge to edge sharpness, and a tiny bit more CA. That's why I have non flip tube, so I get the best possible image out of the unit.


Try to check your back focus every now and then, if possible hook up the camera to a larger monitor and check it. A tiiiiny adjustment can mean everything with adapters...
 
Admir said:
I also started out with the RR2. But I got really frustrated with the ammount of bokeh and the soft image. My HMC is a somewhat "soft image" camera to begin with. Many times I wanted to go below F5.6, and doing that with the RR2 was not possible without picking up the grain.

The RR1 is definitly sharper, and has a bit less light loss too, but nothing drastic. The bokeh is definitly more pleasing to me, and reminds a lot of the Letus look you get.

I wouldn't use the RR3. Sure it has less light loss, and almost non additional bokeh compared to the oter Rotorazors. But it has some really bad vignetting going on, that is due to the really thin glass it's made of. It's just not worth it IMO.
I don't know if you have the flip unit, but the flip gives you a bit less edge to edge sharpness, and a tiny bit more CA. That's why I have non flip tube, so I get the best possible image out of the unit.


Try to check your back focus every now and then, if possible hook up the camera to a larger monitor and check it. A tiiiiny adjustment can mean everything with adapters...
Click to expand...


wow , thanks bro , thats alot of usefull information! Much appreciated. Ill skip on the RR3 and use RR1. i have the non flip tube aswell cause i wanted to save on lightloss but i didnt know that it improves edge to edge aswell. Cant wait to install the RR1 tonight.


when you say back focus , is that the same as the colimnation adjustment ( nikon to blade ) or the distance from camera to ground glass RR1

Thanks Chris
 
Just glad I can help =)

You won't regret using the RR1, it's great! With the back focus i mean the focus ring on your camera. If your camera focus is not 100% correct focused on the ground glass, you'll just get a soft image no matter how close you are to nail the focus...

Also, I know that some cameras' built in ND filters some times changes the optical path in cameras. So with the ND filter on, all of a sudden your camera focus to the groundglass isn't correct any longer! This is one of the issues EX 1 and 3 has with adapters. Don't know about the XHA1 but I would do a couple of tests with and without ND's to see what happens.
 
Admir said:
Just glad I can help =)

You won't regret using the RR1, it's great! With the back focus i mean the focus ring on your camera. If your camera focus is not 100% correct focused on the ground glass, you'll just get a soft image no matter how close you are to nail the focus...

Also, I know that some cameras' built in ND filters some times changes the optical path in cameras. So with the ND filter on, all of a sudden your camera focus to the groundglass isn't correct any longer! This is one of the issues EX 1 and 3 has with adapters. Don't know about the XHA1 but I would do a couple of tests with and without ND's to see what happens.
Click to expand...


thanks for ND info , the xh-a1 has 2 nd positions. and i would have never guessed that just flipping nd on would make the focus unfocused. good to know:) i gotta order another RR1 from Wayne because i though i had dust on mine and used the wrong side of the pen. not the brush side and it left these black streaks. Then i tried using a solvent to fix it which didnt work. :(
 
Baddgsx said:
thanks for ND info , the xh-a1 has 2 nd positions. and i would have never guessed that just flipping nd on would make the focus unfocused. good to know:) i gotta order another RR1 from Wayne because i though i had dust on mine and used the wrong side of the pen. not the brush side and it left these black streaks. Then i tried using a solvent to fix it which didnt work. :(
Click to expand...

Well it was first after a lot of research on adapters and cameras in general that I found out about this problem with ND's. The other side of the pen is actually also used to clean glass, but it is a bit harder and is only used if you have some really nasty dirt on. Check those streaks, use the "wrong side" of the pen again and try to get them off, I mean what do you have to lose since you're going to order a new one =P.

Wayne has given me the best service you could ever imagine. He replaced my rotorazors several times even though I bought the adapter bargained... He didn't even ask if I had any type of reciept. He even payed the shipping, USP priority mail directly to the door. If I ever see that guy I'll give him a big hug =).
 
Admir said:
Well it was first after a lot of research on adapters and cameras in general that I found out about this problem with ND's. The other side of the pen is actually also used to clean glass, but it is a bit harder and is only used if you have some really nasty dirt on. Check those streaks, use the "wrong side" of the pen again and try to get them off, I mean what do you have to lose since you're going to order a new one =P.

Wayne has given me the best service you could ever imagine. He replaced my rotorazors several times even though I bought the adapter bargained... He didn't even ask if I had any type of reciept. He even payed the shipping, USP priority mail directly to the door. If I ever see that guy I'll give him a big hug =).
Click to expand...


its shot bro , i tried everything yesterday. so im gonna order a new one. i emailed Wayne, hes been good to me before when a RR1 came to me unbalanced so it wouldnt start sometimes cause of the friction. He replaced that one no charge. i dont expect him to replace this since it was totally my fault but i did ask him for a small discount , what ever he could do. if he couldnt , i totally understand and will order a new one anyways.
 
Aw man, sad to hear that. Yea I also had balancing issues with my rotorazors, but Wayne sent me new ones every time... the last time he wanted me to send it so he could install it and adjust the adapter for me, for free!:laugh:

You'll see that with the RR1 you'll never need to change anything again in it, it gets really sweet!

I did an unofficial video for a bosnian artist using my HMC and SGblade with RR1. It was a pretty much run n gun video, besides some indoor scenes... IMO I got some nice shots, really sharp but still filmic and pleasing...

 
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you have some really nice shots in there. my favorite inparticular is scene 1:01. what frame rate did you shoot in?
 
Baddgsx said:
you have some really nice shots in there. my favorite inparticular is scene 1:01. what frame rate did you shoot in?
Click to expand...

Well it was all shot on my vacation, so I just had to work with what was there... and the story came along as I shot... I shot in both 50 and 25 fps, mostly 50 fps at 720p in order to get the slow mo and smooth feeling to it, but some scenes were done with 25 fps at 1080p.. You can really see how much sharper it can get with 1080p instead of 720... but adding some contrast to the shot is a really good way to add some percieved sharpnes..
 
I used my wide open and had a couple soft spots but overall I loved the look of the sgblade. Shot this film on it. www.fathomsdeepmovie.com
 

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I haven't used a Blade in well over a year and never used the non flip tube, but did you actually compare it to the flip?
As I recall when the flips came out in general they unexpectedly improved the optics noticeably.

Don't know about the XHA1. i know that with my EX-1 I could use my RR-2 and my Nikon lenses with both camera and Nikon iris's wide open.
What lenses are you using. Nikon ED f2.8 zooms are extremely sharp. most Nikon AI type primes are not good wide open. Need to close down a stop or 2
 
Lenilenapi said:
I haven't used a Blade in well over a year and never used the non flip tube, but did you actually compare it to the flip?
As I recall when the flips came out in general they unexpectedly improved the optics noticeably.

Don't know about the XHA1. i know that with my EX-1 I could use my RR-2 and my Nikon lenses with both camera and Nikon iris's wide open.
What lenses are you using. Nikon ED f2.8 zooms are extremely sharp. most Nikon AI type primes are not good wide open. Need to close down a stop or 2
Click to expand...


I have compared them. I know that the Brevis gave a better image with the flip. But the SGblade will give you more lightloss, and less edge to edge sharpness. This has been confirmed by Wayne at Shoot35.
 
Admir , i installed the RR1 and notice quite a difference in sharpness and light loss. i do like the bokeh of the RR2 but prefer the other characteristes over the bokeh. I started to adjust the colimnation and ran into a problem. i unscrewed the 3 bolts slightly and loosened the small one on the side. i thought i would be able to rotate the colimnation ring but i can not. i dont have to pull all three bolts out to turn the ring right?
 
normally you dont have to pulled all three bolts out but in my case i did , the colimnation ring was stuck. maybe some dirt in the fine threads or something. I got and cant wait to goooo shoot35!
 
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