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Old August 1st, 2006, 02:54 PM   #1
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Blooming

Why does the HD100unit "bloom" if you open the iris right next to the camera body? Could someone explain the phenomenon? I have a 1.8 50mm prime lens that is nearly impossible to shoot interiors with. If I dial the iris thing closest to the camera body up past 4.0, it starts looking like someone's old prom pictures from the 80s, all diffused and horrid. The DOF effect goes away too. How can I maximize my interior shooting with such a lens and the HD100 unit? As I've come to understand, the HD100 is a pretty bad low light performer, worse than the XL H1, and HVX is it not? Why does this "blooming" effect occur? Is there anyway to control it? What if one manipulates that focus ring right next to it? Pulling it all the way to the end seems to be the only way to get it to focus and then if you open it up past f4(right?) it will start to do the blooming thing. Isn't it true that 1.8 is pretty bright for a lens? If I got a 2.8 28mm prime lens it would be even darker would it not? What can I do to maximize brightness short of getting a tiny star into the interior I'm shooting?
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Old August 1st, 2006, 05:53 PM   #2
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sorry this isn't an answer

is the hd100 letus available?
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Old August 1st, 2006, 10:09 PM   #3
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This is just a guess since I don't have a letus, but it sounds like the GG doesn't diffuse enough. If the gg doesn't diffuse enough you get a hazy glow effect on the bokeh with shorter focal length lenses or wide apertures, i.e. the same gg will look good for a 150mm f3.5 but bad on a 50mm f1.2 wide open. You'll see this effect on 1500 grit gg, a 350 grit gg looks much better but also loses more light and the grain is more difficult to hide.
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Old August 1st, 2006, 10:51 PM   #4
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hey...hate to sound like an idiot ;) Could I get a definition of Bokeh? It's the one thing I can't find a solid definition for.
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Old August 1st, 2006, 10:55 PM   #5
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It's best to leave it at 4 or more otherwise there can be blooming - but don't freak out (Quyen used to put a stop at around 4 and I am glad he took it off)
you just have to light your scenes well when using this,
though there is a lot less light loss with the Letus than other adapters I have tried
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Old August 2nd, 2006, 02:28 AM   #6
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I'll second to Andy. Usually directly through going lightrays produce such phenomena. You can call it hotspotting as well.
You can make few more troubleshooting steps:
Just do not zoom in so much that edges go out of FOV. Hotspotting appears only center areas(if Your GG is parallel to ccd - i'm sure it is). So is there seen edge areas image without given artifact?. If it is You can be sure that what Andy said is right. You will see edge areas also vignetting do not let bother yourself from that.
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Old August 2nd, 2006, 07:29 AM   #7
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Letus35 HD100

Ralph,

I just received by 'NEW' Letus HD100 adapter yesterday and the images are far superior to the 'BETA' version of this unit. I had a little trial and error on finding the right settings. When I was shooting outdoors naturally I wanted to use the neutral density filters but this caused the image to be too soft with the blooming effect. I took of the ND and used the aperture to reduce the light and it looks sharp and beautiful. If you've noticed on the HD100, the detail needs to be set close to minimum when using the standard FUJI lens but I found that dialing it back to normal produces crisp images when using the LETUS35. If you have Quyen's new unit, all I can say is practice a little to find the right combination of aperture settings in order to stop the blooming. BTW, I was using a Nikon 50mm 1:1.4 D lens in my test yesterday. I will test other lenses today. With only a couple hours of use with this adapter, I have a lot more playing to do....

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Old August 2nd, 2006, 11:00 PM   #8
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Too much light onto any CCD may produce soft images as light spills to adjacent pixels.(my assumption not scientifically proven fact.) The cure is not to overdose the CCD with light.

Does Quyen's current HD100 unit have provision for backfocus adjustment, which in this application becomes relay focus adjustment?

If backfocus is slightly off, a tighter relay lens aperture will restore the image sharpness but in really low light, with object lens and relay lens apertures opened the image will again be soft.

The same issue will be present if ND filters are used to drop the light level.

The published P+S Technik method of adjusting relay focus is valid. Here follows a modified version. I assume the groundglass texture on Quyen's adaptor to be about AO5 or coarser. I may be wrong on this.


Turn off the groundglass motor.

Open relay aperture fully wide.

Close SLR lens aperture until the brightness of the image is normal. The SLR lens aperture should be tighter than f5.6.

Grain on the groundglass becomes evident if the backfocus/relay focus is correct.

If the light level coming through the SLR lens is still too bright, the groundglass texture may remain hidden.

You may have to point the camera at a lesser light source, but in most instances the groundglass texture should become visible.

If there is no visible groundglass texture and the relayed image is also soft, then the relay focus may be need adjustment.

Follow Quyen's own advices on this as my comments only apply in a general sense.
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Old August 3rd, 2006, 08:21 AM   #9
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Bob,

Great tips for those setting up this adapter...

The new HD100 adapter does have a relay focus adjustment and that's pretty much what I did to make sure focus was correct. The image is really sharp compared to the older version and very useable.

Chris
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Old August 3rd, 2006, 02:56 PM   #10
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bokeh

Quote:
Originally Posted by Cole McDonald
Could I get a definition of Bokeh?
Are You sure You found proper thread for that?? ;)

But if You already asked. Bokeh is not definable. It describes phenomena which contains subjects that are definable. Phenomena is out of focus area and sujects are good bokeh and bad bokeh. So, Bokeh would be theory about all that.
Good and bad bokeh are pretty much sujective but they are definable. You have to only know that good and bad are here like black and white. It means bad doesn't mean necessarily unacceptable and visa versa.
So major agreement is that good bokeh is when lightpoint is blurred similar to gaussian curve. Bad bokeh is when lightpoint is blurred by any other formula - usually by more sophisticated formula.
Subjective side is by that defination to draw the line there where gaussian isn't gaussian enough.

have look: http://luminous-landscape.com/essays/bokeh.shtml
there is figure 6 which describe very well mathematically what it's all
about.

Last edited by Frank Hool; August 4th, 2006 at 12:47 AM. Reason: typos
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Old August 3rd, 2006, 04:35 PM   #11
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I picked one of the many threads where it was used...thank you for the definition...or lack thereof within the out of focus area.
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