SgBlade Lenses test

N

naavt

Well-known member
Hi all,

I've returned from a shoot recently which was shot with XH-A1+SgBlade+some lenses.

I'm used to use a Sony camera with the Blade and because I mostly do Docs I've never became much concerned about obtaining the ultimate sharpness from the system. But now I've shot for a B roll on a project that is not mine and came home finding that my footage was way too soft for my taste so I went looking for the reasons why it looked that way.

First, I've found that my collimation was of by a turn and a half! So I've set it up right finding that the Blade collimation ring has to be on it's maximum clockwise position to obtain the proper mark-to-focus setup.

Second, I went and recorded some seconds from my dining room window to the outside with various lenses which I'm posting bellow. The XH-A1 settings were:

- 0db gain
- z73 zoom
- 0,9m focus (back focus)
- AGC off
- ND off
- preset WB to 5500K
- Iris set to f4.8

- Blade was spinning slightly above half speed with RR1

The following pics were exported from FCP with QT conversion to TIFF files with best depth. Then pixel corrected in Photoshop (from 1440x1080 to 1920x1080) and saved as JPG at 10 quality. No correction was done.

I don't know how to post full resolution images in photobucket (don't know if it even accepts it), so if anyone wants to see the full 1920x1080 please advise me on how to share it.

I'll be appreciated if you could make whatever comments you may find useful.
Thanks

Sigma 28mm f1.8 @ 5.6
http://i82.photobucket.com/albums/j272/naavt/Sigma28mmf1856.jpg

Sigma 24-60mm f2.8 @ (50mm) 5.6
http://i82.photobucket.com/albums/j272/naavt/Sigma24-60mmf2850mm56.jpg


Sigma 24-60mm f2.8 @ (24mm) 5.6
http://i82.photobucket.com/albums/j272/naavt/Sigma24-60mmf2824mm56.jpg

Nikon 85mm f2 @ 5.6
http://i82.photobucket.com/albums/j272/naavt/Nikon85mmf256.jpg

Nikon 50mm f1.4 @ 5.6
http://i82.photobucket.com/albums/j272/naavt/Nikon50mmf1456.jpg

Nikon 105mm Micro f2.8 @ 5.6
http://i82.photobucket.com/albums/j272/naavt/Nikon105mmMicrof2856.jpg

Canon XH-A1 @ 4 ND filter on 1.6x
http://i82.photobucket.com/albums/j272/naavt/CanonXH-A1f4.jpg



I've assembled the Blade achromat upgrade prior the shooting (which I had never used before), and I am now thinking if I've done it properly :(
 
Last edited:
on my xha1/sgblade setup, if its soft its always because the backfocus is off. Even if it's sharp one day, I'll always readjust it before every shoot to make sure it is spot on.
 
bimdas said:
on my xha1/sgblade setup, if its soft its always because the backfocus is off. Even if it's sharp one day, I'll always readjust it before every shoot to make sure it is spot on.
Click to expand...

Thanks. I am really certain that backfocus was right though. GG pattern was clearly visible when it was not spinning.
 
naavt said:
Thanks. I am really certain that backfocus was right though. GG pattern was clearly visible when it was not spinning.
Click to expand...


Ok! It was off by a 10th of a meter!

I was under the impression that XH-A1 iAF really worked but no! I've assembled the whole rig again and pushed the iAF button. Once again the camera focused at 0.90m but now I've played a bit with the backfocus and realized that perfect focus is obtained at 0.80m... Not 0.90 :(

So thanks bimdas (and Wayne from shoot35 who was - once again - really helpful replying to my emails), for your assistance.

None of this never happened with the Sony cameras since they are always backfocus manually, and that's what I've should done with XH-A1 in the first place :(
 
I was completely confused by this post and din't respond because you used the term back focus incorrectly. Back focus refers to the 35mm lens on the adapter screen. You are referring to the video camera's focus on the screen for which there is no special term. Its a common misunderstanding but leads to confusion.

Lenny Levy
 
I've read the blade manual a bunch of times but i still don't understand that backfocus thing. How exactly am i suppose to do it. right now the 50mm lens goes to infinity and then out of focus. if you goes could list the steps of adjusting the backfocus i'd really appreciate it.

btw im using an hmc150, sgblade, fd mount, 50mm, 28mm

thanks
 
Hi,

This means that the 35mm lens & mount face is too close to the ground glass. You must loosen the 3x screws that holds the mount to the SGblade, and also the small setscrew on the red collimation ring. Once loosened, you should turn the red collimation ring clockwise (looking from the front) by small amounts like an 8th of a turn, re tightned the mount and test. Keep making changes until you can focus on infinity when the focus ring hits infinity. Also check that your focus marks read correctly, i.e, 1m on the lens focuses @ 1m.
 
Lenilenapi said:
I was completely confused by this post and din't respond because you used the term back focus incorrectly. Back focus refers to the 35mm lens on the adapter screen. You are referring to the video camera's focus on the screen for which there is no special term. Its a common misunderstanding but leads to confusion.

Lenny Levy
Click to expand...

i always thought the focus from video camera to groundglass was the backfocus? Distance from gg to lens is something to do with microcollimation?
 
ok i have another question. so im using canon fd and obviously i cant adjust the aperture of the lens unless i do that trick with the toothpick. I have my lens wide open, it's a 50mm 1.4, now does this mean every shot i do i'm going to see a lot of grain? Because i still dont get that whole stopping down past f4 thing. i have the blade and its a spinning adapter, my canon lens is wide open and sometimes i have the iris on my cam wide open, is this bad? Should the lens be at f4 and i light the shot according to that or can the lens remain wide open and i stop down the iris on the cam to f4? I think i was doing it wrong the whole time.

Thanks
 
the wider open the lens the less chance of grain. IF you have the rr1 you will have less chance of grain at most f-stops. If you have rr2, then you have to be carefull with how much you close the lens before you start seeing the circle grain patterns.
 
Marduk said:
I have my lens wide open, it's a 50mm 1.4, now does this mean every shot i do i'm going to see a lot of grain?
Click to expand...

At 1.4 it's very very unlikely that you see any grain at all with the GG spinning. Don't forget that the f stop you use on your camera lens is also very important. If you do close it all the way you probably will get some grain with some GGs, like RR2 fo instance.


Marduk said:
Because i still dont get that whole stopping down past f4 thing.
Click to expand...

I've made many shots with the RR1 GG with the SLR lens way past f/4. Many even at f/11 with no visible grain.

Marduk said:
i have the blade and its a spinning adapter, my canon lens is wide open and sometimes i have the iris on my cam wide open, is this bad?
Click to expand...

Normally any lens has it's sweat spot. If you can hit it all the time when you shoot you are probably going to end with better footage. I've found that the best settings with the XH-A1 is around f/4 to f/5.6 but sometimes you are struggling for light, so F/4 is way close in those situations.

Besides image quality alone, you have much more probabilities of ending with a out of focus image due to a bad camera lens to GG focus, so I advise you to close your camera iris a bit after focusing on the GG.


Marduk said:
Should the lens be at f4 and i light the shot according to that or can the lens remain wide open and i stop down the iris on the cam to f4? I think i was doing it wrong the whole time.

Thanks
Click to expand...

Sorry if I didn't quite understood your questions here, but nonetheless, here's my workflow:

I ask myself what kind of DOF I want for a particular shot.
I always try to maintain my camera lens between the sweat spot, normally at f/4.
I light the scene accordingly to the SLR f stop I want to use in the first place.

Hope that helps
 
interesting.....i always thought that the more open the lens is (lower fstop number like f1.4 f2.8 f4 f5) the more chance of grain you will see but the higher fstop number (f8 f11 etc..) the less grain of the gg you see because less light going through the lens to show that gg grain.

so i usually shoot my scenes at f5 f4 f8 but changing the aperture on my canon fd is a pain. so lately what i've been doin is keeping it wide open at 1.4 and using my camera iris to stop down. the dof is really shallow i know but i try to work with it just because the time it takes to pop the lens of, rig it so it tricks the lens and change the aperture setting, then unrig it and pop it back on only to realize that i stopped down a little too much. now i need to go back up an fstop only to repeat the whole thing over again

anyways thanks for the info guys
 
Marduk said:
interesting.....i always thought that the more open the lens is (lower fstop number like f1.4 f2.8 f4 f5) the more chance of grain you will see but the higher fstop number (f8 f11 etc..) the less grain of the gg you see because less light going through the lens to show that gg grain.

so i usually shoot my scenes at f5 f4 f8 but changing the aperture on my canon fd is a pain. so lately what i've been doin is keeping it wide open at 1.4 and using my camera iris to stop down. the dof is really shallow i know but i try to work with it just because the time it takes to pop the lens of, rig it so it tricks the lens and change the aperture setting, then unrig it and pop it back on only to realize that i stopped down a little too much. now i need to go back up an fstop only to repeat the whole thing over again

anyways thanks for the info guys
Click to expand...

You just need to put a piece of wire or a tooth pick in the rear of the Canon FD lens (where the fitting is springed and can be pushed, etc) then you can adjust the aperture of the lens with it on the blade.
 
You must log in or register to reply here.
Back
Top