How does one stop make such a difference??!!

Discussion in 'Nikon' started by christina_santavicca, May 14, 2009.

  1. Hello. So, as I further my studies into exposure, and I just analyze some of my past photos, I am just baffled as to how 1 stop makes such a difference. You can see the difference in color between the two. Is there just a little trick I need to know, or will it just always be this intricate and precise to this extreme? Thanks guys.
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  2. An increase in exposure by 1 stop = double the amount of light hitting the film/sensor. It is quite a significant difference.
     
  3. You may want to look elsewhere for this color shift as f/4 to f/4.2 is NOT a one stop difference; not even a half stop difference.
    Pete
     
  4. This should really have been a part of your other thread. Splitting up the same topic like this makes it difficult to offer advice.
    First, if your aperture values listed are correct, the difference between f/4 and f/4.2 is not 1 stop.
    [[You can see the difference in color between the two]]
    This has nothing to do with exposure. I would say it probably has something to do with your choice of auto white balance and your difference in framing between the two. If you're shooting RAW, color correction is so simplistic that one should really not worry about these slight changes.
     
  5. ShunCheung

    ShunCheung Administrator

    I'd say the difference is largely white balancing. The Auto WB is probably not consistent.
     
  6. Ok Pete, i'm kinda relieved to hear you say that. Wher else do you think i should look for the problem??
     
  7. Ok Rob. well i do shoot raw, but i'd like to get the image right the first time, alleviating alot of post processing work. (maybe that's in a perfect world??) and so are you suggesting that since i did reposition my framing, that the camera would'v changed wb choice?
     
  8. I'll just copy/paste my comment from your other version of this thread, to generally address that topic... though I agree - now that I see your examples - that you weren't actually asking an exposure question as much as a WB question, as Shun points out. As for how one stop (ignoring WB for a moment) can make a visible difference:

    It all depends on how you come by that one stop.

    For example: if you leave the shutter speed and aperture alone, and just raise ISO by one stop, you might introduce noise and lose detail. If you gain one stop by opening up a lens's aperture by one stop, you might (it depends on the lens!) lose some contrast and sharpness. If you gain one stop by doubling the amount of time the shutter is open, you might introduce motion blur (in the camera, or by the subject) which robs you of detail and clarity.

    So (in roughly the same order), you can mitigate the situation by using a camera that tolerates higher ISOs better, by using lenses that still produce sharp, contrasty images when wide open, or by using a camera support (like a tri/monopod) or image stabilization technology when using slower shutter speeds.

    Or, add more light! Of course, then you have to talk about how you add more light, and whether the quality of that light is helping matters or making them worse (the deer-in-the-headlights strobe-on-the-camera blast, for example, is a high price to pay for more light). Or, shooting at noon instead of at 8:00AM will certainly get you more light, but it will also get you harsh shadows and the need for very high dynamic range.

    It's all about compromises, and making the ones that best serve (or least get in the way of) the image you wish to create.
     
  9. Auto WB is just the camera making an educated guess about the nature of the light. So, even a small change in the framing can certainly alter the clues the camera is using to make that guess. It only takes a moment to set up a custom WB when shooting indoors in artificial light, and if you don't want to shoot a WB target and correct after the fact, the custom WB can really help out.
     
  10. [[and so are you suggesting that since i did reposition my framing, that the camera would'v changed wb choice?]]
    Yes.
    [[but i'd like to get the image right the first time]]
    I don't know your post-processing workflow but I can apply the same WB value to two or two hundred photos with a few mouse clicks. (Some people take a reference shot with a gray card or white balance card and use that frame to apply a WB value to subsequent shots in post production.)
    However, you can always turn of Auto White Balance and set it to a specific value when you take the shot. All that means is, instead of doing work in post processing, you'll be doing more work at the time of the shot. There is nothing wrong with that, of course, everyone has their own approach to how they shoot.
     
  11. Ah, Matt beat me to the punch.
     
  12. Ok. thanks so much men :) and OK OK .... so i pretty much repeated my dizzy problem from my other thread ..... what can i say .... i'm just still a newbie all around *wink* - I do appreciate all the help tho guys, as i make my way through (i feel) these final wrinkles b4 i may actually have some type of secure handle on exposure :)
     
  13. And i do recall learning about taking the gray card shot for future adjustments in post processing. that is one i need to write down right now so that it sticks :) - thank you, that will help alot.
     
  14. The titles of your shots show exposure difference of f4.0 to f4.2. Is that right, or a typo? That's not one stop. Going from F4.0 up to F5.6, or down to F2.8, would be one stop.
     
  15. Yeah, sorry, that's right. 4.0 to 4.2 you'll just have to excuse my ignorance of not knowing that wasn't a full stop *blush*
     
  16. - 0.2 is not 1 stop
    - Auto WB could work differently
    - SB600 may flashed differently (bouncing angle, recharge, etc.)
    - natural light could change outside (if there is a window in a room)
     
  17. I don't like auto WB because then WB becomes this moving target that I have to adjust for later in post. Are you familiar with the canned WB settings on your camera?
     
  18. by "canned" do you mean the preset settings?? and yeah, i know em, but i thought auto wb wld b easier, however, i did not know that it could fluctuate like this. so i should reconsider the convenience as an inconvenience perhaps.
     
  19. also, i had wondered if it had something possible to do with flash also. that's why i had listed it in the photo details. thx for the awareness that the possible lack of recharge?? should be something to consider as well. and i believe there was a small window across the room, but do you think it'd make that much of a difference?? in the color cast? - i really don't know is why i ask :)
     
  20. Here are the usual aperture full "stops":
    1.4, 2, 2.8, 4.0, 5.6, 8.0, 11, 16, 22
    Each is double or half it's neighbour's area, ie: let's in twice or half as much light. With most modern slr/dslr cameras showing 1/3 or 1/2 stop increments, it's kind of hard to keep track of the full stops, both for aperture and shutter speeds.
    The usual full stop shutter speeds are:
    1, 2, 4, 8, 15, 30, 60, 125, 250 and so on.
    "1" representing one second, "2" representing 1/2 second, and so on.
     
  21. well, no one said it before, but i like your picture: you put an interesting angle and composition on what i normally turn into a boring and static scene. now, another thing that's gonna be weird to you: with your sb600 in auto mode, adjusting your aperture is gonna do weird things, like probably nothing at all. the auto program of the sb600 will just kick up the juice to compensate, so you're gonna have a photo with a little more artificial light than natural light. things get weird with auto stuff, and the results are not really repeatable. i wish the flash would show what setting it used, let you dial that in on manual, and go from there. is your sb600 sitting on top of your camera or is it off camera somewhere (if it is not, go to strobist.com and learn why flash is so much fun)
    That being said, your comparison is also good for you: you can see tone. Now maybe when you're shooting something, you will set your white balance a little warm like the first one and go for that tone or maybe a cooler wb will set the image in your head to a file. either way, keep having fun, and don't think that any misteps you make have never been performed before you.
     
  22. ahh, a nice dose of encouragement. thanks Mr. Sutton :) and i have gone to strobist on numerous occasions, but quite honestly, can't get through some of his rambling to grasp the point, lol. maybe it's an anxious personality problem on my account, haha, or maybe i just need to try again. would you suggest anywhere in particular that i go? i've gone to lighting 101.
     
  23. p.s. Mendel, thank you. i greatly appreciate the lesson on full aperture and shutter stops, i am keeping a note of them :)
     
  24. well, if your camera has a commander mode, you can pull your sb600 off of your camera and start moving it around, put socks over it to diffuse it, all kinds of fun stuff. i'll bet a good investment is some colored saranwrap (i have never spelled that before so don't think i'm dumb haha). but look at the lighting 102. that's where i started as it seems to get a little more to the point quicker. but there is some good help there, and even if you don't follow the tutorials, it will get you thinking on the right track about artificial light. i need to add an sb600 to complement my sb900 as i think that two lights is when you really get into fun.
    now don't think that i'm some old time shooter; i've only been shooting for maybe 5 months. But one book that i've read that has really helped me understand the camera is ansel adam's the negative. you should be able to find this at your library, either school or public. This will teach you everything you'd like to know about exposure from one of the technical masters of photography; adam's style may not be for everyone but his technical prowess was legendary. I cannot advocate this book enough.
     
  25. I'd say the difference is largely white balancing. The Auto WB is probably not consistent.​
    You are shooting at 1/10 per second (dragging the shutter). It also looks like you have a mix of tungsten light, and flash; which cast two different colors. This will always cause WB problems if you don't add a gel to your flash. In this case I see a bit of orange (compared to green) so I am going to guess it is tungsten light.

    My suggestion for this situation. Throw an orange gel on your flash and set WB to Tungsten. This would give you the proper WB in this photograph. These are generally included with the SB-800/900, but you can still buy them separate for your SB-600.

    Under fluorescent you do the same thing but w/ a green gel.

    I hope this helps. If someone already posted the same advice, I apologize as I didn't have time to read the entire thread. If you get a chance, Nikon does teach a Flash workshop where they have reps travel to different dealers. The generally for free because they want you to buy their flashes. They go over using gels for correct WB in the workshop.

    Also worth noting. If you have two different WBs in a photos (flash on subject, tungsten in background) you cannot fix this in post. Your flash must be gelled to match the other light source.
     
  26. Ok. I know my library does have a few of his books, i'll have to check again to see if one of them was that one. otherwise, i did recently pick up 3 diff books on lighting/exposure, so i'v started into those yesterday (i hate reading, lol) and i will try the lighting 102, maybe that one will be more tolerable. OH!! and yeah, i've tried tissue paper over my light for diffuse.... and it caught on fire, hahaha. Think i might try gary fong's lightsphere II. something not so flamable, lol, and a little more productive.
     
  27. Keith, thanks so much. i've been wondering about the gels and such. As i just mentioned, i'm considering the lightsphere, and i know you can get the different colored domes, but i didn't know if it was very necessary, and from what you say it is. and it makes sense about the not being able to fix that in post production. Thanks so much, and ur safe.....ur the 1st one to mention about color for the flash :) Also, very cool about checking into nikon's free workshops. I didnt know that they did that. i'll be checkin into that right away :) thanks
     
  28. As far as the gels go... you can use them directly with your SB-600, the Light sphere isn't required. What the light sphere will do for you is diffuse the light. I haven't used one, so I can't really comment on how effective it is. I'm sure if you do a search of the forums you will find lots of information on the lightsphere and other gary fong products.

    You might try just getting some plain old gels before investing in a diffuser and see how you like them. You can get them in sheets and cut them out (they are just colored plastic sheets), or get the Nikon one which are already cut out. They are inexpensive.
     
  29. The difference between f/4 and f/4.2 is too small to be signifificant. However, most of the light may have been provided by the flash. God knows, what exactly it did. I suspect the flash to be the reason for these two differently exposed pics. Switch off the flash and try again. The difference should be gone.
     
  30. Great! Thanks so much :)
     
  31. White balance or flash can give these variations. It certainly is not because the f-stop change, which is too small to have any significant effect.
    --Lannie
     
  32. Christine,

    I was just reminded....Expodisc also does a free workshop on white balance. They of course are pushing their products, but I found the workshop very informative.

    I'm sure the availability of these workshops might also differ depending on geography, but I live in a fairly small population area, and we still get a free workshop about once every 1-2 months.

    Best of luck to you!
     
  33. Auto white balance is a wonderful thing, especially if you're shooting raw. (Think you said you were.) What good cameras can do is amazing - but it can be a bit finicky, too.
    I can't tell if there's a window in this room - looks like there is, though, and if so, and it's day time, something as simple as a cloud can change partially obscuring the sun can change the white balance noticeably. This is the kind of variation that drives photographers into studios, where they can control the light totally.
    The other thing I am wondering about is your crop. You didn't mention whether the second shot was cropped. But it's NOT the same composition exactly. Looks like you moved slightly to the left before taking the second shot. That means that the colors you're capturing aren't quite the same - and that too could make a difference to the camera's guess regarding proper white balance.
    Keep shooting raw. I find that auto white balance and the "as shot" white balance option in Lightroom 2.3 works more than 80% of the time. 10% of the time Lightroom's "auto" adjustment seems about right. Only 10% of the time - no, probably less often than that - do I have to futz manually with the white balance, using the eye dropper etc. That's with my Pentax K20D but I bet others shooting raw + auto WB get similar results.
    Will
     
  34. Hi Christine
    I think the explanation for this variation is that you used spot metering. An interesting experiment would be to repeat this, placing the spot on 2 different colours in the scene and try to retain the same exposure details.I would like to see these taken again in Matrix metering mode, which would be the preferable setting for flash. IMHO,The bottom image also contains more blue than the top image hence the colour balance change. The bluer content could have influenced the colour shift and "corrected" the more yellow top image..
     
  35. I'll reiterate what others have been saying about AWB. My sense is that the colors aren't so completely off each exposure that flash consistency might be a likelier candidate, as somebody indicated.
    I'm trying to be delicate here, but I also need to advocate, in conjunction with your other thread regarding lens speed, that you really need to get a better grasp on basic exposure concepts in terms of physics of light, the concept of a "stop", etc., rather than think about this largely as a matter of camera dial settings. It's going a little backwards, IMHO. Once you understand exposure, everything else, to the extent there is anything else, is pretty straightforward. And this goes twice if you're planning to charge for your services in the very near future.
    Now the nicer part - since you're using Nikons and an SB-600, you should not only look at strobist, as you are, but also this blog, which takes you step by step through how the Nikon CLS flash system works. If you start at the beginning, the author does a great job walking through how the Nikon cameras compute flash and fill flash and how to use your flash off-camera, which you can already do without buying another accessory. But once again, it makes the most sense if you're well-grounded in exposure concepts.
    http://nikonclspracticalguide.blogspot.com/
     
  36. Keith, thx again for the info. I'm currently checking n2 the workshops with Expodisc. But it is just as George stated, that i really do need a better grasp on exposure. I just can't seem to fully get it. I know fully (well, atleast i think i do) what each individual aspect alone does, but it just seems that when it comes to combining them all together, the further i get into learning, i just get taken out like a tidal wave. i mean, (if sum1 can giv me sum cheese for my wine for a minute) i'm not a slow learner, pretty intelligent actually, i just cant seem to get it !!! lol What the *beep* is my problem! is this normal?? i don't know. but all the advice and input here really does help carry me along. and Peter, i wondered also if the metering might have had something to do with it also, that's why i had specified that in the detail, so thank you for the input there. Thanks to all. Lord help me. lol
     
  37. Christina,
    One reason you might feel as if you're not "getting it" is the fact that you're struggling with a number of factors all at the same time, and all of them are moving targets. Sure, you know the relationship between aperture and shutter speed, and perhaps even ISO, but now you've added several other components on auto-pilot, such as flash and white balance.
    Here is a thought - try setting everything on manual, then keep testing and adjusting until you get it the way you like. Lets say you did that with the scene above - shoot a dozen different images or two dozen, change _one_ thing each time, and note what changes. Exercise all the dials, and you'll see its really straight forward - sort of like watching a juggler juggle a single tennis ball. WB shifts between yellow and blue, adding flash changes both exposure and color, ISO adds noise, and so on. Right now you're watching someone juggle about 6 tennis balls, and everything looks like a blur, and telling yourself you don't get it. Of course! But if you break everything down to its individual cause and effect, it will make sense as a whole.
    You have been getting wonderful responses to this question, and a lot of good information. However, the information is making understanding more complex. Complexity is good once the basic fundamental relationships are fully understood.
    For example, mixed light scene (more than one type of light - flash, daylight, shade, bulbs, florescent) is always a color challenge. Simplify by avoiding mixed light until you've mastered single light sources.
    Best,
    Bob
     
  38. With the flash on AUTO, going from F4 to F4.2 would cause the flash to work just a bit harder, and more of the exposure to result from the flash, which is "whiter" than the ambient light. I would think that this alone would account for at least part of the difference in the color cast.
     
  39. One thing I forgot - well I also forgot which camera you're using - it takes a little knowledge to know how to set everything to manual. Basically, choose any white balance except A, make sure auto-ISO is off and set the camera to a single focus spot and finally choose mode M. If you use a flash, make sure that's showing a nice big M, or better yet skip the flash for a moment.
    b
     
  40. Jim, i appreciate the flash working harder, providing "whiter" light. That's information i hadn't known. And Bob, yes you are very right, i do need to set the camera on a tripod, in an area where the light remains unchanged and just go to town. I do shoot in manual mode, as well as manual for wb and iso as well. oh, and i have a baby D60. and i like your analogies of the moving targets and the juggler :) Thank you.
     
  41. One more thing with the white balance. If you're shooting under fluorescent, most of them change colour at twice the AC supply frequency (therefore 120Hz in the US, 100Hz most other places), shifting along a green-to-orange axis. So if your shutter speed is shorter than about 1/100, then you can get frame-to-frame random colour variations even if using a fixed WB setting.
    You mention a desire to "get it right in camera" and this is an admirably good approach, but it's not relevant with respect to WB if shooting RAW unless you have multiple sources of light. If there is just one light source, the RAW file contains all the recorded information, which is unaffected by WB settings. So you set the WB in postprocessing and it's absolutely no different to setting it in-camera.
    The major exception to the "shoot RAW, forget WB" is where you mix light sources, you typically want their colour to match, which often means putting gels on a flash and/or turning fluorescent lights off. If there is a colour mismatch between your light sources, you really need to get that fixed before taking the shot as it's practically impossible in post.
    One more thing: if under strongly coloured light, like dim tungsten, you will find that there is a lot of red light and very little green/blue. That means that your camera is likely to blow the red channel on its sensor and therefore lose all detail, so you have to watch your histogram very carefully. And once you correct the WB in post, you may find that the colour imbalance introduces more blue noise than you would necessarily expect because you're effectively shooting the blue channel at much much higher sensitivity to get a neutral result.
    If you have sodium-vapour lamps (yellow streetlights) then forget WB altogether - there is only a tiny notch of spectrum available and it contains no green or blue. You can never get correct colour from such light sources because they just don't contain enough spectrum.
     
  42. Wow William, i need to learn so much, lol. I've done so much studying up to this point, and right now, i feel as if i've done none at all, haha. Thank you for your feedback. it's great information that will help :)
     

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