Different exposures with camera set to manual?

<p>There seems to be a lot of questions about panoramas these days, but this is less about the actual panorama technique and more about why I would get such vastly different exposures with my camera set on full manual?</p>

<p>Below is a panorama shot that I threw together on a whim , thinking that I might start trying to do more of these due to the fact that I no longer have a super-wide lens after switching to DX format. I was using my new (to me) D50 with AF 50mm 1.8 D. The three images were taken with the camera set on manual, 1/125 sec at f16, no exposure compensation, ISO 200. I verified through EXIF data that the settings did not change. The shots were taken within seconds of each other. The lighting was from a very overcast sky (very diffuse light) with no wind, which I thought would be the ideal situation for maintaining exposure throughout the scene. I wasn't paying much attention at the time, but I checked to see that the shots do overlap each other by a good bit.</p>

<p>The shot I'm posting involved only a half-hearted attempt at stitching the shots together (I don't have a stitching program yet) and no post processing, other than converting to jpeg by Nikon Picture Project 1.5. The NEF versions show differences in brightness also.</p>

<p>The entire shot is horribly underexposed (i forgot to recalculate shutter speed after stopping down for DOF). Would this exaggerate differences in light quality?</p>

<p>Metering was set to spot, but that shouldn't matter with the camera in manual mode, right?</p>

<p>I'll try to post a second (properly exposed) shot taken with my 24mm, for reference.</p><div></div>

<p>Reference Shot</p><div></div>

<p>i think spot metering contributed to the differences. try not to use spot on your second sample.<br /> and take note of all variables.......but hey, that was great without a stitching program. have fun.</p>

<p>@Ramon - why would the metering mode make a difference - the camera was set to manual. <br>

According to the EXIF - Auto White Balance was on - and the images show differences in color cast. The underexposure by almost two stops doesn't help much either.</p>

<p>Was AEB turned on by mistake? Metering mode shouldn't make a difference in this situation. BTW, the second photo still looks underexposed on my screen.</p>

<p>This happens to me all the time with my D50. I've learned to ignore it, especially since I never go panoramas or things that require more than one frame.</p>

<p>I suspect there is some exposure correction applied during the conversion process. This correction is usually based on the entire image. In addition, Photoshop (or other stitching program) may make exposure corrections. A dedicated stitching program like PTGui tries to even out variations, whereas ACR and Photoshop try to optimize each image individually.</p>

<p>Did you have a polarizer on the lens?</p>

<p>I don't know if this helps, but I'll post a stitch of a couple of screen caps i made from Picture Project. I don't have a program yet that allows me to stitch NEF files. Hopefully this will adequately show the difference in brightness between the NEF files (note the differences in the water).<br>

AEB was not on. Never use it. The only filter on the lens was a L37c UV filter.<br>

I'm beginning to lean towards the auto white balance brought up by Dieter as balance being the difference maker.</p><div></div>

<p>dieter,<br>

maybe it's just my practice of not using spot metering when i intend to stitch that prompted me to share the concern to cory. of course there are other variables to look into and i am for sure not an expert.</p>

<p>Is the ISO auto setting on ? What are the ISO settings of the pictures in question. On my camera (Nikon D50) I think the ISO is adjusted even in manual mode if set to ISO auto.</p>

<p>What did you spot meter on ? I assume you metered for the first shot and then ignored the meter reading after that.<br>

Any exposure compensation set by mistake ?</p>

<p> </p>

<p>Auto ISO will still work with the camera in manual mode though you would probably see the different ISOs in the exif. Did you process the NEFs at exactly the same settings?</p>

<p>Were you setting the aperture via the camera body, or via the aperture ring on the lens? Note that setting via the camera body can sometimes result in some inconsistency, not normally noticeable, but in critical applications like time lapse photography or stitching, it can become significant. See this thread:</p>

<p>http://www.photo.net/nikon-camera-forum/00JpSP</p>

 

<p>Your D50 captures the light that is there. Your eyesight can correct for a variety of bright and dark areas, making the average just right. The clouds (even though not in sunlight) are not evenly illuminated (for lack of a better comparison,) so the D50 recorded the light to the camera sensor in a (to you) uneven fashion. You could try to bracket your exposures and see if the results are more to your liking.</p>

<p> </p>

<p>I did some paroramas with my D200 on full manual including WB and ISO, and the exprosures were very consistant. I did use spot metering, but I only used manual lens (such as 28mm f2 AI) though. I did not know D50 but I would try a full "full manual" if I were you (say, manual WB, set the aperture on the lens as suggested above).</p>

<p>I done some pano on my D70 and they were constant. If you had any diff exposures it would be at the end of one other end but the gradation from left to right was smooth.....</p>

<p>I say put everything in manual, exposure, WB, focus. <br>

IMO that is too much from what I am seeing.</p>

<p>Do you have a stuck aperture arm? I had to repair mine.<br>

Easy test is just take rapid frames of the same subject and see if you get the diff exposures. You can also test it by looking at the lens, choose f/2.8 or something and keep pressing the dof button repeatedly ... if failure you will see the lens closing all the way down.</p>

<p>Ok, I'll try to answer most of these questions, but it's getting late and I have to work early tomorrow. The ISO didn't change between exposures, I verified this through EXIF data. If i remember correctly, I metered on the sky and opened up two or three stops. then I stopped down for DOF and forgot to change the shutter speed (hence the underexposure). I don't think there is a problem with the aperture arm, it moves smoothly when i move it by hand and i havent noticed any problems with my N75 when i press the DOF preview button at f22. I set the aperture on the lens at f22 (the minimum) and use the camera to control the aperture per the manual's instructions. Also I verified that there was no exposure compensation set.</p>

<p>Thank you to everyone for all your posts. It's time for bed now. I'll check back tomorrow after i get home from work.</p>

<p>It was auto something.</p>

<p>The terrific underexposure may be contributing somehow since the sky is the dominant feature left.</p>

<p>Noise reduction turned off? White balance put on cloudy or daylight?</p>

<p>Try it again after doing a proper metering, which can be done by chimping a test shot and looking at the histogram. Then, make sure everything is turned off or put to a manual setting.</p>

<p>If all settings were manual with auto iso off and auto WB off there should be no such effect in RAW images if these were shot in rapid sequence to exclude changes in light.</p>

<p><strong>Check your EXIF data if all images were shot with the same exposure time and aperture as well as WB.</strong></p>

<p>If you still see the effect (I bet 100:1 that this is not the case if all is set properly) then try to reset the camera - it indicates a "hidden pilot error".<br>

If RAW images were converted and the effect all the sudden appears in the converted images then there is some "auto" setting in the image conversion.<br>

<strong>@Edward</strong> - my PS version CS4 does not try any "optimization" of individual images when I do automatic stitching :-) On the contrary it will try to reduce edge effects between images. ACR should not be considered in the context of stitching. It is easiest to find a cure if one looks at the images that enter the stitching process :-)</p>

<p>First find out if the problem occurs "upstream" of the stitching.</p>

<p >To do panoramas-</p>

<p >for panoramas- -use tripod. you must keep it level with the horizon. if your tripod does not have a level builtin then buy one that slides into your flash hotshoe. again make a max effort to get the camera level.</p>

<p >-for exposure. set the exposure by pressing halfway and noting the fstop and shutter speed. you are trying to find the brightest part of you panorama scene to be. once you have found the brightest check the fstop and shutter speed. put camera into manual metering mode and use those settings. do not change them for any part of the panorama.</p>

<p >-lens selection. i shoot mine with a 20mm. note: SHOOT THE LENS VERTICALLY. this is the only way to get some vertical scene, otherwise the panorama will be shaped like a hotdog. Note- if the panorama is a vertical panorama then you shoot landscape. this is why i went to a 20mm. in vertical you are cutting your angle of view way down. my tripod has degrees engraved in the mount, i was shooting at only a 15 degree spread and in looking at the shots before stitching there wasn't that much overlap. i later shot panoramas with 35mm 50mm 70mm; the hot dog effect was more pronounced. the panorama itself did work. With higher mm lens you would have to go to double rows.</p>

<p >-determine in advance the center point of the scene and try to go X number of shots on each side of it. for me with my setup a 120 degree scene is 7 shots; the center and 3 on each side. if i go with a 35mm lens then a 120degree scene will take 13 shots. no matter what lens you use realize that you are adding only 33% new scene with every shot, the rest is overlap for the right and left adjoining shots. the only exceptions are the end shots in the whole scene. it is possible to add another row above and/or below the first one. this would help the vertical look especially if you are using a 50mm or longer. for multiple rows are the same as 1 row, but you know have to overlap on the vertical as well as the horizontal. you must make sure that there are no gaps.</p>

<p >- i stick my hand in front of the lens and shoot, then shoot the panorama, the 7 shots, then put hand in front of lens and shoot. later i know that everything between hands is the panorama.</p>

<p >-i have used cs2 or the panorama factory software to make the panorama. for either couldn't be simpler simply select the shots and it does the work. this is where using a level pays off. the software is leveling the scene to make the long rectangle, but if the scene was not as level as possible in the first place the vertical becomes less and less(you end up with hotdog shape). so having the tripod and camera level is very important. also when mount and shooting vertically make sure the camera really is vertical, carefully check by looking threw the viewfinder. some tripod vertical adjustments actually go past true vertical, mine does even though it says 90 degrees.</p>

<p >-be sure to use a cable release or the selftimer.</p>

<p >-on focusing- what i do is to simply preset the 20mm lems at infinity, because of depth of field everything from 5.64ft to infinity is in focus at f11.0 distance 200ft. you can also use a hyperfocal focus setup. but thanks to the DOF table, just setting the lens at infinity is simpler. -i left WB alone, that is set at AWB; or you can use a preset setting like sunny or cloudy, but once set do not change it till panorama shots are done.</p>

<p >-online depth of field calculator available here- <a title="Click to open link in a new browser window" href="http://www.dofmaster.com/dofjs.html" target="_blank">http://www.dofmaster.com/dofjs.html</a> </p>

<p >-parallax error. It is usually not so much a problem outdoor shooting. This is because the distances are greater than inside. In any event if you shoot panoramas outside and at short distances OR any inside any building, you should be thinking of getting a panorama tripod head. This is to eliminate parallax error. I have the panosaurus pano head, cheap durable, and it works.</p>

<p >-for panoramas, the software i use is either panorama factory orPTGui or cs2. the one that works best for me is PTGui. i have since gotton PTGuiPRO, expensive but worth it. has many features and abilities that the other software does not have, including the ability to process 360 and 720degree spherical panoramas, plus many projection types and it does raw and hdr panos.</p>

<p >-on post shooting work. If jpeg DO NOT PP. just use as is. After the pano is made then pp as desired. If raw, does your panorama software do raws? Not all do. If yes raw batch convert only. Do not adjust any 1 shot. All shots must be the same before the pano is made, then do any pp you wish but on the whole pano.</p>

<p >If any pp work is done to the pano before stitching then there will be a difference in the sections, and you could(probably?) get vertical bands where the sections join. </p>

<p >Any questions, please ask. gary</p>

<p>Do you have a post processing program that allows you to manually set white balance? If so, run it through that and see if the problem is the same.</p>

<p>I don't know why people are mentioning metering when you say that all shots were taken in manual mode with the same settings...</p>

<p>A <em>free</em> good stitching option that helps evening out the differences in white balance and exposure (up to a point): <a href="http://research.microsoft.com/en-us/um/redmond/groups/ivm/ice/">Microsoft ICE</a>.<br>

Maybe worth to give that a try (since all the other programs mentioned by others cost money), and I think you'll find that in the end doing it manually is a lot of work and extremely tricky to get completely right. If you're running a Windows PC, this program is certainly worth the try.</p>

<p> It may be your shutter failing? How many pictures you've taken with this camera?</p>

<p>My guess is the reasons for the variations could be as follows: 1) not manually setting white balance 2) NEF to JPEG converter is not consistent.<br>

Cory...if you are serious about doing panoramas, I would suggest using PTGUI. I believe they have a free 30-day trial. It will blend minor color differences very well for you. It's a great program.</p>