Under-exposed images/Aperture and the FX1000/Lens ramping at DVinfo.net

Jeff Harper · January 3rd, 2009, 05:54 AM

When running the VX2100, if I needed to set the exposure on a face for a closeup, I would zoom in on the subject, set the iris and then record. Perfect.

However when I do this with the FX1000 the behaviour is different.

In manual, I zoom in on the face but the iris ring becomes useless and the image way too underexposed, dark.

This is how it is supposed to be according to the manual, but I don't understand it. The following is taken directly from page 34 of the manual:

"The F value becomes close to F3.4 as the zoom position changes from W to T even when you open the aperture by setting the F value lower than F3.4, such as F1.6". In other words, as I zoom in on the face, the image becomes dark and no good and no amount of fiddling with the iris ring will change it.

Luckily, after taping a rehearsal last night it appears that running in iris in auto will work out in the chapel today as the lighting appears to be very even and sufficient. But this will not always be the case, and for the photo session I don't know what I will do. Extreme closeups of faces are absolutely essential with my shooting style, and this is not a good situation at all.

I forget who it was but someone, (Tom H possibly) described the phenomenon above as lens ramping. Is this something that can be overcome, or is there a setting in the menu to limit this behaviour?

How does one zoom in and avoid the lens ramping?

Tim Akin · January 3rd, 2009, 07:32 AM

Good question Jeff, I would also like to here some discussion on this.

I'm guessing to overcome this you would have to move in closer or gain up.

Jeff Harper · January 3rd, 2009, 07:41 AM

Tim, I found a discussion of the issue at the below link.

From what I am reading there if your camera does it, it does it and cannot be changed. I believe this is the trade-off for having a 20x zoom. The only solution is to not zoom in for extreme closeups. This is a REAL bummer for me as extreme closeups are a feature of my videos and are important to me and are expected by people who have seen examples of my work, they love the extreme closeups.

I will have to try to work around it by not zooming in so much, but during the ceremony I cannot move closer, so this is a very sad development for me. I have a friend with an FX1, and I might investigate it, as I suspect it does not suffer from this issue. I may need to buy one for front ceremony camera for photo sessions, if it indeed doesn't have the lens ramping issue.

Video Lenses: How They All Work

Tim Akin · January 3rd, 2009, 07:48 AM

Jeff, we seem to have similar styles so this would be a problem for me also. Maybe someone has a work around with AE shift or something, of coarse that would mean auto exposure. I thought this might be a problem when I was playing around with the cam.

Thanks for the link.

Jeff Harper · January 3rd, 2009, 08:00 AM

It is a problem for sure Tim. It is so disappointing I'm sitting here totally dejected, I just bought my second FX1000, as you know. I would have tried using an FX1or Z1 with my first FX1000 if I had known about this.

I wonder if using an add-on lens would be useful? I don't understand optics very well, so I don't know. What does the signature of the one guy around here say? "Instructions? I just want to push buttons!" That sums me up pretty well, though I'm not proud of my lack of technical knowledge.

For today I have to work with what I have.

Jeff Harper · January 3rd, 2009, 08:34 AM

Disregard post

Hans Ledel · January 3rd, 2009, 08:34 AM

I you had read the Tech spec of the FX1000 you would have seen the F values are "F 1.6 -3.4"
That means that at W you can open up to F1.6 and at 20X zoom you can only use 3.4 and that is how a zoom lens works.

The Z1/FX1 have an F 1.6 - 2.8 and the reason for this is that the lens on the FX1 is "only" 12X

I´m sorry to say this, but this is something very basic about zoom lenses that you should know.

Cheers

Hans

Tim Akin · January 3rd, 2009, 08:40 AM

Jeff, In good lighting I don't think there will be a problem, most of the time the lighting is good on the alter. I was just looking at some of the footage we shot at the reception from the cam on the tripod, with light, when the cam was zoomed in it got very dark. We will just have to learn what we can and cannot do to get good useable footage.

Don't get down, these are great wedding cams, we just have to give ourselves time to learn them.

Jeff Harper · January 3rd, 2009, 08:42 AM

Ok Hans. Thanks a lot.

You're right Tim. At least being armed with this knowledge I can stop banging my head and instead try to work with it.

Terence Murphy · January 3rd, 2009, 08:55 AM

I don't think a FX1/Z1 would solve your problem, as it is probably at about the same aperture for a given level of zoom (but without the 12x-20x range), and has less sensitivity to boot.

You might be able to adapt your shooting style by setting the exposure to work for your wider shots (e.g. f2.4 and however much gain needed), and either toggling in another +6 dB of gain when you zoom in for extreme close-ups (to compensate for the lens ramping to f3.4), or switching to auto-gain for the close-ups (on the assumption that lighting will be relatively uniform in the field of view so auto should work well. Just make sure your AE shift is set to something that works well ahead of time). The hard part is to remember to switch back to manual-gain when you zoom back out.

-Terence

Jeff Harper · January 3rd, 2009, 09:33 AM

Thanks Terence. No matter how it's sliced I think the days past of my "amazing closeups" of the brides at the altar are history. I have been playing around with it this morning trying to use gain to compensate but it has gainy look, just not the same.

I'm about to play with the AE shift setting for the first time, thanks for the suggestion.

Jeff Harper · January 3rd, 2009, 09:38 AM

Been playing with the AE shift during the closeups it doesn't seem to have any effect actually, but for wider shots I can see it's usefullness. Thanks for your suggestions!

Tim Akin · January 3rd, 2009, 09:51 AM

Jeff, make sure you play with the AGC. Set it to limit the gain to a desired level in case to switch to auto gain.

Alex Goldshteyn · January 3rd, 2009, 10:58 AM

That's one of the advantages of the Z7u over the FX1000/Z5 that folks fail to mention. It has a F1.6-2.0 12x lens and with the digital extender turned on you, I believe you effectively get 18x at F2.0. Having used the digital extender on this cam, I can tell you that the image quality change is virtually unnoticeable even when projected on a 52" LCD.

Steve Renouf · January 3rd, 2009, 11:03 AM

As the physical properties of the zoom lens cannot be changed (and as someone previously mentioned, it is a physical aspect of ALL zoom lenses; to a higher or lesser degree) your best bet would be to "fix" the aperture at f3.4 so that it stays the same throughout the zoom range

January 3rd, 2009, 05:54 AM	#1
Jeff Harper Inner Circle Join Date: Jun 2005 Location: Cincinnati, OH Posts: 8,425	Under-exposed images/Aperture and the FX1000/Lens ramping When running the VX2100, if I needed to set the exposure on a face for a closeup, I would zoom in on the subject, set the iris and then record. Perfect. However when I do this with the FX1000 the behaviour is different. In manual, I zoom in on the face but the iris ring becomes useless and the image way too underexposed, dark. This is how it is supposed to be according to the manual, but I don't understand it. The following is taken directly from page 34 of the manual: "The F value becomes close to F3.4 as the zoom position changes from W to T even when you open the aperture by setting the F value lower than F3.4, such as F1.6". In other words, as I zoom in on the face, the image becomes dark and no good and no amount of fiddling with the iris ring will change it. Luckily, after taping a rehearsal last night it appears that running in iris in auto will work out in the chapel today as the lighting appears to be very even and sufficient. But this will not always be the case, and for the photo session I don't know what I will do. Extreme closeups of faces are absolutely essential with my shooting style, and this is not a good situation at all. I forget who it was but someone, (Tom H possibly) described the phenomenon above as lens ramping. Is this something that can be overcome, or is there a setting in the menu to limit this behaviour? How does one zoom in and avoid the lens ramping? Last edited by Jeff Harper; January 3rd, 2009 at 07:01 AM.

January 3rd, 2009, 07:32 AM	#2
Tim Akin Major Player Join Date: Nov 2008 Location: Newbern, TN Posts: 414	Good question Jeff, I would also like to here some discussion on this. I'm guessing to overcome this you would have to move in closer or gain up. __________________ Tim

January 3rd, 2009, 07:48 AM	#4
Tim Akin Major Player Join Date: Nov 2008 Location: Newbern, TN Posts: 414	Jeff, we seem to have similar styles so this would be a problem for me also. Maybe someone has a work around with AE shift or something, of coarse that would mean auto exposure. I thought this might be a problem when I was playing around with the cam. Thanks for the link. __________________ Tim

January 3rd, 2009, 08:34 AM	#7
Hans Ledel Regular Crew Join Date: Jun 2005 Location: Stockholm Sweden Posts: 184	I you had read the Tech spec of the FX1000 you would have seen the F values are "F 1.6 -3.4" That means that at W you can open up to F1.6 and at 20X zoom you can only use 3.4 and that is how a zoom lens works. The Z1/FX1 have an F 1.6 - 2.8 and the reason for this is that the lens on the FX1 is "only" 12X I´m sorry to say this, but this is something very basic about zoom lenses that you should know. Cheers Hans __________________ Remember, that English is my second language.

January 3rd, 2009, 08:40 AM	#8
Tim Akin Major Player Join Date: Nov 2008 Location: Newbern, TN Posts: 414	Jeff, In good lighting I don't think there will be a problem, most of the time the lighting is good on the alter. I was just looking at some of the footage we shot at the reception from the cam on the tripod, with light, when the cam was zoomed in it got very dark. We will just have to learn what we can and cannot do to get good useable footage. Don't get down, these are great wedding cams, we just have to give ourselves time to learn them. __________________ Tim

January 3rd, 2009, 07:41 AM	#3
Jeff Harper Inner Circle Join Date: Jun 2005 Location: Cincinnati, OH Posts: 8,425	Tim, I found a discussion of the issue at the below link. From what I am reading there if your camera does it, it does it and cannot be changed. I believe this is the trade-off for having a 20x zoom. The only solution is to not zoom in for extreme closeups. This is a REAL bummer for me as extreme closeups are a feature of my videos and are important to me and are expected by people who have seen examples of my work, they love the extreme closeups. I will have to try to work around it by not zooming in so much, but during the ceremony I cannot move closer, so this is a very sad development for me. I have a friend with an FX1, and I might investigate it, as I suspect it does not suffer from this issue. I may need to buy one for front ceremony camera for photo sessions, if it indeed doesn't have the lens ramping issue. Video Lenses: How They All Work

January 3rd, 2009, 08:00 AM	#5
Jeff Harper Inner Circle Join Date: Jun 2005 Location: Cincinnati, OH Posts: 8,425	It is a problem for sure Tim. It is so disappointing I'm sitting here totally dejected, I just bought my second FX1000, as you know. I would have tried using an FX1or Z1 with my first FX1000 if I had known about this. I wonder if using an add-on lens would be useful? I don't understand optics very well, so I don't know. What does the signature of the one guy around here say? "Instructions? I just want to push buttons!" That sums me up pretty well, though I'm not proud of my lack of technical knowledge. For today I have to work with what I have.

January 3rd, 2009, 08:42 AM	#9
Jeff Harper Inner Circle Join Date: Jun 2005 Location: Cincinnati, OH Posts: 8,425	Ok Hans. Thanks a lot. You're right Tim. At least being armed with this knowledge I can stop banging my head and instead try to work with it.

January 3rd, 2009, 08:55 AM	#10
Terence Murphy Regular Crew Join Date: Mar 2006 Location: Baltimore, MD Posts: 161	I don't think a FX1/Z1 would solve your problem, as it is probably at about the same aperture for a given level of zoom (but without the 12x-20x range), and has less sensitivity to boot. You might be able to adapt your shooting style by setting the exposure to work for your wider shots (e.g. f2.4 and however much gain needed), and either toggling in another +6 dB of gain when you zoom in for extreme close-ups (to compensate for the lens ramping to f3.4), or switching to auto-gain for the close-ups (on the assumption that lighting will be relatively uniform in the field of view so auto should work well. Just make sure your AE shift is set to something that works well ahead of time). The hard part is to remember to switch back to manual-gain when you zoom back out. -Terence

January 3rd, 2009, 09:33 AM	#11
Jeff Harper Inner Circle Join Date: Jun 2005 Location: Cincinnati, OH Posts: 8,425	Thanks Terence. No matter how it's sliced I think the days past of my "amazing closeups" of the brides at the altar are history. I have been playing around with it this morning trying to use gain to compensate but it has gainy look, just not the same. I'm about to play with the AE shift setting for the first time, thanks for the suggestion.

January 3rd, 2009, 09:38 AM	#12
Jeff Harper Inner Circle Join Date: Jun 2005 Location: Cincinnati, OH Posts: 8,425	Been playing with the AE shift during the closeups it doesn't seem to have any effect actually, but for wider shots I can see it's usefullness. Thanks for your suggestions!

January 3rd, 2009, 09:51 AM	#13
Tim Akin Major Player Join Date: Nov 2008 Location: Newbern, TN Posts: 414	Jeff, make sure you play with the AGC. Set it to limit the gain to a desired level in case to switch to auto gain. __________________ Tim

January 3rd, 2009, 10:58 AM	#14
Alex Goldshteyn New Boot Join Date: Jun 2006 Location: Chicago, IL Posts: 17	That's one of the advantages of the Z7u over the FX1000/Z5 that folks fail to mention. It has a F1.6-2.0 12x lens and with the digital extender turned on you, I believe you effectively get 18x at F2.0. Having used the digital extender on this cam, I can tell you that the image quality change is virtually unnoticeable even when projected on a 52" LCD.

January 3rd, 2009, 11:03 AM	#15
Steve Renouf Regular Crew Join Date: Dec 2008 Location: Jersey, GB Posts: 182	As the physical properties of the zoom lens cannot be changed (and as someone previously mentioned, it is a physical aspect of ALL zoom lenses; to a higher or lesser degree) your best bet would be to "fix" the aperture at f3.4 so that it stays the same throughout the zoom range

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search