Board index Photography Technical Questions Adjusting EV for 1.4x converter

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Adjusting EV for 1.4x converter

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jimva
 
Posts: 26

Adjusting EV for 1.4x converter

Post Sun Oct 18, 2009 8:01 pm


I have a Nikon D90 that I purchased a 1.4x lens converter for. I have yet to figure out the right way to compensate exposure for it. Any suggestions?

prinothcat
 
Posts: 662

Re: Adjusting EV for 1.4x converter

Post Sun Oct 18, 2009 9:01 pm


which methods have you tried so that we don't cover old ground?
Chris

dougj
 
Posts: 2276

Re: Adjusting EV for 1.4x converter

Post Sun Oct 18, 2009 10:03 pm


A 1.4x increases the f-stop by 1 stop, f/4 becomes f/5.6. On Canon bodies, if the teleconverter is the reporting type, the camera will see the aperture plus the 1.4x TC and adjust the automatic exposure accordingly, Nikon probably works the same way. If you're doing manual calculations and exposure, use the 1 stop difference in the calculations.

jimva
 
Posts: 26

Re: Adjusting EV for 1.4x converter

Post Sun Oct 18, 2009 10:56 pm


To answer Chris's response I placed it on the camera set the camera to auto thinking it would compensate. I would the same scene with and without and the converter and the exposure seems way under on the converter shot. So really I have not tried much. I thought what would happen is Doug's response. It is not a expensive converter could it be the camera does not reconize it. Thanks for the help!

dougj
 
Posts: 2276

Re: Adjusting EV for 1.4x converter

Post Sun Oct 18, 2009 11:56 pm


jimva wrote:To answer Chris's response I placed it on the camera set the camera to auto thinking it would compensate. I would the same scene with and without and the converter and the exposure seems way under on the converter shot. So really I have not tried much. I thought what would happen is Doug's response. It is not a expensive converter could it be the camera does not reconize it. Thanks for the help!


Some TCs are the non-reporting type, they are a pass-through, consequently the camera believes the apertures are those reported by only the lens and the non-flash metering will be off by about 1 stop. To overcome this, you can simply dial in +1 exposure compensation and tune it with the histogram. The reason some TCs don't report is that on some cameras the AF is automatically disabled when the maximum aperture goes below f/5.6-f/8. At these (small) apertures the projected image circle might or might not adequately cover the AF sensors, so at least Canon disables AF, Nikon might be different. There are some 3rd party long telephoto zoom lenses that do something similar - they do not report apertures smaller than the value at which AF is disabled by the camera.

It's easy to test and see if your TC is reporting - mount the TC and lens and see what the maximum aperture is that you can set in the camera.

jimva
 
Posts: 26

Re: Adjusting EV for 1.4x converter

Post Mon Oct 19, 2009 10:29 pm


I do believe my TC is reporting. I was under the impression that changing EV meant changing F stops. This D90 is changing shutter speeds in P mode. At least I was able to get a better pic by changing the EV. But changing shutter speeds confuses me because I thought I was compensating F stops

dougj
 
Posts: 2276

Re: Adjusting EV for 1.4x converter

Post Tue Oct 20, 2009 1:15 am


If the TC is reporting, I would expect the camera to receive the correct aperture information for the lens and calculate exposure the same as without the TC. I don't know the Nikon modes, Canon adjusts both SS and aperture in P mode, unless the photog overrides one of them. There may be more going on in the P modes, depending on the manufacturer and models. If you want to select a specific SS, you may want to consider a different mode. In most of what I shoot, I tend to use a mode that permits me to set the aperture so I can control DOF, then let the camera set the SS. Sports shooting may be different, in that the SS is the priority. I use the shutter speed priority mode, while the camera sets the aperture.

prinothcat
 
Posts: 662

Re: Adjusting EV for 1.4x converter

Post Tue Oct 20, 2009 3:20 am


jimva wrote:I do believe my TC is reporting. I was under the impression that changing EV meant changing F stops. This D90 is changing shutter speeds in P mode. At least I was able to get a better pic by changing the EV. But changing shutter speeds confuses me because I thought I was compensating F stops

Changing EV is both adjusting F-Stop and shutter speed. Note too that a higher ISO is also a way of changing your EV. All will do the job. A slower shutter speed will have the effect of adding light the same way that opening the aperture will. The down side of slow shutter speed is of course less chance of stopping motion including camera shake. The down side, if you will, of opening up as Doug mentioned is loss of Depth Of Field. Using a high ISO will allow a faster shutter and a smaller F-Stop. This decreases undesired blur from subject motion and camera shake. The smaller F-Stop will increase your DOF. I'm starting to get off track aren't I... In P mode on your D-90 if only the shutter speed is changing, I suspect something is amiss. I'm a sports shooter primarily, therefore I tend to set my shutter for the best possible speed and let the camera handle aperture. As long as I pay attention to it so that I get adequate DOF. I suggest, you set a fixed shutter speed and then point the camera with the TC/Lens combo around the room at varying light sources and see if the camera compensated by changing your F-Stop.
It occurs to me that we have not asked an important question. That is simply what len(s) are you trying this TC with? Some are simply not TC compatible. You may want to check with the lens manufacture are see if this is the case. I'm somewhat certain that most of the consumer grade Nikon lenses don't play well with TC's. For instance I know that my Nikkor 80-200 2.8 which is pro grade will not take a TC of an kind. It simply will not meter. The electrical contacts are in the wrong place.

mauisp
 
Posts: 10

Re: Adjusting EV for 1.4x converter

Post Tue Oct 20, 2009 6:59 am


I have a Tamron pro 1.4 that I use with my Nikon 70-300mm Afs VR. Everything seems to work other than it does not report the exif data correctly.
I normally shoot shutter or aperture priority and set my EV to -03 or more underexposed. As with the TC on my photos get overexposed even when set at 0.0EV. By the way it's on a Nikon D60. Underexposed seems to work fine for me. :)

jimva
 
Posts: 26

Re: Adjusting EV for 1.4x converter

Post Tue Oct 20, 2009 11:46 am


First I want to say thanks to everyone who has helped me with this issue. I have a older Nikkor 7-300 4.5/5.6 AF-S for this D90. I did a few test shots +1 and -1 EV and was able to get better exposures. I believe +1 was the better of the two. I have read (more than once) everyones replys and will practice all of them and shoot and shoot and shoot. Thanks Again!

prinothcat
 
Posts: 662

Re: Adjusting EV for 1.4x converter

Post Wed Oct 21, 2009 2:25 am


jimva wrote:First I want to say thanks to everyone who has helped me with this issue. I have a older Nikkor 7-300 4.5/5.6 AF-S for this D90. I did a few test shots +1 and -1 EV and was able to get better exposures. I believe +1 was the better of the two. I have read (more than once) everyones replys and will practice all of them and shoot and shoot and shoot. Thanks Again!

Sounds like you're on the right track. Something else to watch, that we have not touched on, is that the TC is going to drop the effective maximum aperture on that lens to close to 5.6. At this point Many AF systems including Nikon's will start to have trouble focusing properly unless that image has a large range of contrast. It's a factor of the AF itself, and as far as I am aware not something you can compensate for. Best of luck as you experiment further.
Chris


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