Softness at maximum zoom

David Esp · May 19th, 2008, 11:57 AM

I often have to site the Z1 at the rear of audiences, far from the subject. At almost maximum zoom, even in well-lit situations, the image invariably looks soft. Clearly the best option is to site the camera more closely. However this is not always practical or acceptable, so a couple of thoughts:
a) Is there a replacement lens or a telephoto add-on option to permit full sharp HDV-resolution images at such distances and zoom levels? I am considering obtaining a 35mm adaptor, which may be relevant.
b) For the Z1 as given, assuming mid-range f-stop (say), what's the greatest zoom level one can use before the softness effect essentially violates the "high definition"? By this I suppose I mean when the circle of confusion (due to imperfect lens, not DOF) is the same size and an HDV pixel.

Boyd Ostroff · May 20th, 2008, 01:02 PM

I think something else may be going on here.... I shoot performances from the back of the theatre, over 100 ft from the stage, and never noticed the "soft" phenomenon you describe. I use a Century 1.6x teleconvertor lens on my Z1, and it helps me move in a little closer.

Are you focussing manually while you're zoomed all the way in? If you focus while wide and then zoom in, you might get softness at full zoom since focus is more critical there (less depth of field). I find that autofocus doesn't work well for performances.

Also, what is the sharpness setting in your picture profile? I find the default a little too soft for my liking and have kicked it up a few notches.

David Esp · May 20th, 2008, 02:05 PM

The same softness has happened on many gigs at nearly full zoom where the scene is typically a single speaker, Wide to Mid Shot. With camera on a locked steady tripod, I normally zoom in fully and use expanded focus view, sometimes with peaking. I have also tried using temporary (push button) autofocus in case I made a mistake. Sharpness has always been 11. Iris at the most recent gig, which was well-lit, was a comfortable f3.7 with 0dB gain and 1/50 shutter. I tend to underexpose slightly, in order to get clean highlights (levels to be raised and curved off gently in post).

My colleague always sits nearer to the speaker (10-20 ft) using a Sony TRV33 DV handycam on auto-focus, achieving a clearer image overall (despite more jpeggy artefacts etc.). Embarrassing! At shorter range though, like 20ft, the Z1 image is as expected sharper than the TRV33.

Ervin Farkas · May 20th, 2008, 09:30 PM

I'm afraid something is wrong with the optics of your camera; try renting another one and confirm. As Boyd stated, there are no known issues with the sharpness on the Z1.

John M. McCloskey · May 21st, 2008, 08:28 AM

We have 10+ of the Z1U's and all of them zoomed all the way in with focus set at infinity are a tad bit out of focus. All the Field Producers here know to go to infinity and barely move back with the focus ring almost to infinity but not to infinity and that seems to bring everything into a crisp focus. It took us a while to figure this trick out but seriously all of our cameras see this issue and the trick works with everyone of them, back off of infinty just a bit. THX

David Esp · May 22nd, 2008, 03:48 PM

Curious! I'll have to try comparing with another Z1 then. Many thanks for the replies.

Boyd Ostroff · May 24th, 2008, 02:34 PM

Quote:

Originally Posted by John M. McCloskey

We have 10+ of the Z1U's and all of them zoomed all the way in with focus set at infinity are a tad bit out of focus.

Well I think you may be over-generalizing here. How far away is the subject when you find max zoom at infinity to be out of focus? I'm not sure how far away "infinity" is on the Z1 at max zoom, but it's pretty far. Shooting performances, our singers are anywhere between 110 to 150 feet from the camera. If I zoom in all the way and set focus to infinity, they won't be in focus. But that's not a flaw in the Z1, they just aren't at an infinite distance yet. Looking at the distance readout on the Z1, IIRC I see a range between about 32 to 36 meters in the conditions above.

I think David is using the correct methodology: zoom all the way in, switch to expanded focus, and make the image sharp. Before shooting a performance, I do this for various locations on the stage and make a mental note of the distance readout (in meters) so I can have some confidence with manual focus on the fly as I shoot.

If you are going to infinity, then backing off a bit, you're probably getting it into the ballpark but it really depends on exactly how far away the subject is and what your iris opening is. Since our operas tend to be rather dark, I'm almost always shooting wide open and that makes focus more critical.

May 19th, 2008, 11:57 AM	#1
David Esp Regular Crew Join Date: Apr 2007 Location: Alton in Hants and Swanage in Dorset, UK Posts: 45	Softness at maximum zoom - knowledge & fix? I often have to site the Z1 at the rear of audiences, far from the subject. At almost maximum zoom, even in well-lit situations, the image invariably looks soft. Clearly the best option is to site the camera more closely. However this is not always practical or acceptable, so a couple of thoughts: a) Is there a replacement lens or a telephoto add-on option to permit full sharp HDV-resolution images at such distances and zoom levels? I am considering obtaining a 35mm adaptor, which may be relevant. b) For the Z1 as given, assuming mid-range f-stop (say), what's the greatest zoom level one can use before the softness effect essentially violates the "high definition"? By this I suppose I mean when the circle of confusion (due to imperfect lens, not DOF) is the same size and an HDV pixel.

May 20th, 2008, 09:30 PM	#4
Ervin Farkas Inner Circle Join Date: Aug 2005 Location: Atlanta/USA Posts: 2,515	I'm afraid something is wrong with the optics of your camera; try renting another one and confirm. As Boyd stated, there are no known issues with the sharpness on the Z1. __________________ Ervin Farkas www.AtlantaLegalVideo.com

May 20th, 2008, 01:02 PM	#2
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,787	I think something else may be going on here.... I shoot performances from the back of the theatre, over 100 ft from the stage, and never noticed the "soft" phenomenon you describe. I use a Century 1.6x teleconvertor lens on my Z1, and it helps me move in a little closer. Are you focussing manually while you're zoomed all the way in? If you focus while wide and then zoom in, you might get softness at full zoom since focus is more critical there (less depth of field). I find that autofocus doesn't work well for performances. Also, what is the sharpness setting in your picture profile? I find the default a little too soft for my liking and have kicked it up a few notches.

May 20th, 2008, 02:05 PM	#3
David Esp Regular Crew Join Date: Apr 2007 Location: Alton in Hants and Swanage in Dorset, UK Posts: 45	The same softness has happened on many gigs at nearly full zoom where the scene is typically a single speaker, Wide to Mid Shot. With camera on a locked steady tripod, I normally zoom in fully and use expanded focus view, sometimes with peaking. I have also tried using temporary (push button) autofocus in case I made a mistake. Sharpness has always been 11. Iris at the most recent gig, which was well-lit, was a comfortable f3.7 with 0dB gain and 1/50 shutter. I tend to underexpose slightly, in order to get clean highlights (levels to be raised and curved off gently in post). My colleague always sits nearer to the speaker (10-20 ft) using a Sony TRV33 DV handycam on auto-focus, achieving a clearer image overall (despite more jpeggy artefacts etc.). Embarrassing! At shorter range though, like 20ft, the Z1 image is as expected sharper than the TRV33.

May 21st, 2008, 08:28 AM	#5
John M. McCloskey Major Player Join Date: Jun 2005 Location: West Point, MS Posts: 313	We have 10+ of the Z1U's and all of them zoomed all the way in with focus set at infinity are a tad bit out of focus. All the Field Producers here know to go to infinity and barely move back with the focus ring almost to infinity but not to infinity and that seems to bring everything into a crisp focus. It took us a while to figure this trick out but seriously all of our cameras see this issue and the trick works with everyone of them, back off of infinty just a bit. THX

May 22nd, 2008, 03:48 PM	#6
David Esp Regular Crew Join Date: Apr 2007 Location: Alton in Hants and Swanage in Dorset, UK Posts: 45	Curious! I'll have to try comparing with another Z1 then. Many thanks for the replies.