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Thread: Couple questions...

  1. #1

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    Couple questions...

    Hi All,

    Been a while since I've posted, but I am still a frequent visitor.

    As I read various magazines, websites and books on photography, I come across the use of exposure compensation. I've ask a photography teacher in the past: "Is EC the same as changing the shutter speed to achieve the same result?" His answer was simply "Yes".

    So, my question to the collective is; if this is true, why is EC referred too so often? Personally, I would prefer to play with the shutter directly since EC changes it anyway. What are your thoughts?

    Additionally, when reading all these periodicals, it is repeated to have an f/stop of around f/8 to optimal sharpness. However, if shooting is a zoo and the subject is over 10 meters away and I'm using a 300mm lens at 100mm, the DoF is fairly large at f/5.6 and f/8. Is sharpness, in this case, a question of lens optics or DoF?

    Hope these questions have made sense.

    Thanks,

    Erik

  2. #2
    Administrator Manfred M's Avatar
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    Re: Couple questions...

    Hi Erik - I'm afraid that your photography teacher was not quite correct in his response to you; or at least way he said was correct only if you are shooting in aperture priority mode. In modern camera, we control three variables to get correct exposure; sensitive (ISO), aperture and shutter speed. If we shoot in one of the fully automated modes; shutter or aperture priority we tell the camera to lock down one of the variables and adjust the other for the correct exposure. If there is something about the scene that you are shooting that causes over or under exposure (for instance a shot in the snow or on a white sand beach; i.e. a scene that is not 18% gray), you have to manually override your light meter's reading to get the correct exposure.

    Because the your camera moves in lock step in these modes; in aperture priority, if you increase your aperture opening, your camera will automatically select a higher shutter speed, in shutter priority, a similar thing happens; if you shoot a faster shutter speed, the camera will automatically open the aperture wider to compensate. EC lets you override this lock-step link between these two settings so that you can correct for this meter reading issue.

    If you shoot in manual mode, EC is totally meaningless and you can manually chose the appropriate level of compensation. If I chose to shoot in program mode, were the camera selects the appropriate aperture and shutter speed and on my camera is adjusts both the aperture and shutter speed. In theory, you could also adjust the ISO value and leave the aperture and shutter speed set.

    In your second question you are confusing depth of field and lens sharpness. DoF is just the distance where objects are sharp enough, i.e. they are "in focus". The smaller the aperture that we shoot with, the greater the depth of field.

    The f/8 maximum sharpness that you are reading about is something else altogether. We all know that a lens is not as sharp as it can be when it is wide open. Simple optics tells us that at wider apertures, the lens has to bend the light at sharper angles and this ultimately results is some loss of sharpness (as well as potentially introducing other aberrations). As we stop down, the light travels through the central part of the lens, and is bent less, resulting in a sharper image. As we step down further, another optical effect called diffraction comes into play. When a light wave (any wave really) passes through a narrow opening, it bends and so becomes less sharp. In general, the lens is sharpest in the f/5.6 - f/8 range that you mention.

    That being said, with high quality lenses, we make conscious decisions an shoot at sub-optimal apertures to get the compositional effects that we want. To your example, a landscape shot that has part of the subject out of focus is less acceptable than the tiny bit of softening we get from diffraction to get everything in focus. If we are shooting wide open to get narrow depth of field and want to throw the background out of focus, we have purposely shot at an aperture that may not be as sharp as possible, but have opted to make this trade-off to give us a soft background.

  3. #3

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    Re: Couple questions...

    Well articulated, Mafred. EC is confusing to many people and you explained it well.

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    Re: Couple questions...

    EC refers to changes in the shutter speed when in Aperture Priority and changes in the aperture when in Shutter Priority. So, it does not always affect shutter speed. I am with you though about switching to manual focus when the scene demands a lot of EC maneuvering. It is much easier for me to spot meter on the extreme tones and get a feel for the correct exposure that way then guessing and checking in Aperture Priority. Often--no hard and fast rules here.

    Your confusion with the types of sharpness comes down to the difference between the plane of focus and the zone of acceptable sharpness one calls the depth of field. The plane of focus is composed of the focal point and all the other points that are equally distant from your sensor. A brick wall directly facing you, for example. It is this plane that is reported to be resolved best by an f stop around f 8. When we refer to sharpness, we are talking about this plane. The zone of acceptable sharpness is on each side of the plane of focus. Points that are not on the plane of focus but are in this zone are not actually sharp--just acceptably sharp. The size and quality of this zone is affected by the choice of f stop with smaller f stops typically improving the appearance of sharpness in this zone--to a point. Going smaller does not, however, improve the sharpness of the plane of focus typically past f 8. For me, it is usually a question of what is more important: the sharpness of a flat surface or the overall clarity of the scene. That will change scene to scene.

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    Re: Couple questions...

    Could someone clarify and expand on the meaning/uses of using exposure compensation in Manual Mode on a Nikon D80 (any Nikon DSLR I think?) with the iso set to auto?

    Thank you.

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    Re: Couple questions...

    Quote Originally Posted by Christina S View Post
    Could someone clarify and expand on the meaning/uses of using exposure compensation in Manual Mode on a Nikon D80 (any Nikon DSLR I think?) with the iso set to auto?

    Thank you.
    If you are in manual with shutter and aperture but auto ISO and you set EC to +1, then the ISO will increase exposure by one stop above the meter reading.

    For example, let's say you had ss =100, f stop at 8, and auto ISO and you take a shot. You look at your preview and see that the camera chose ISO 200. Then you set EC to +1 and take the exact same shot without touching ss or aperture. The camera would adjust the ISO to 400 whch is one full stop (or EV) higher exposure than the previous shot.

  7. #7
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    Re: Couple questions...

    Thank you for a wonderful explanation (beautifully simple) and example.

    Quote Originally Posted by NorthernFocus View Post
    If you are in manual with shutter and aperture but auto ISO and you set EC to +1, then the ISO will increase exposure by one stop above the meter reading.

    For example, let's say you had ss =100, f stop at 8, and auto ISO and you take a shot. You look at your preview and see that the camera chose ISO 200. Then you set EC to +1 and take the exact same shot without touching ss or aperture. The camera would adjust the ISO to 400 whch is one full stop (or EV) higher exposure than the previous shot.

  8. #8

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    Re: Couple questions...

    Quote Originally Posted by GrumpyDiver View Post
    If you shoot in manual mode, EC is totally meaningless and you can manually chose the appropriate level of compensation.
    There is one situation that I disagree, Manfred, about exposure compensation being meaningless. Assume that you have selected the ideal shutter speed and aperture for whatever look you want with regard to those two factors. However, also assume that you are using auto ISO and the resulting exposure is not what you want. You will need to adjust the exposure compensation to affect the ISO.

    Alternatively, you could shoot in fully manual mode by not using auto ISO. However, if you are switching back and forth, as an example, between using aperture priority and manual mode, you might want to leave the camera in auto ISO. That's because switching in and out of auto ISO can be more cumbersome due to having to use menu items rather than knobs or buttons on the exterior of the camera.

  9. #9

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    Re: Couple questions...

    Quote Originally Posted by Christina S View Post
    Could someone clarify and expand on the meaning/uses of using exposure compensation in Manual Mode on a Nikon D80 (any Nikon DSLR I think?) with the iso set to auto?
    That stuff is easy to forget, Christina, especially considering the complexity of factors pertaining to the use of auto ISO. To get a quick refresher course, simply set your camera to a particular situation. Look through the view finder, change a particular setting, and watch the changes to the information being displayed in the view finder. In the example of your question, you would see that all information remains unchanged except that the exposure information and the ISO value change.

  10. #10
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    Re: Couple questions...

    EC in manual mode with flash also handles the flash output (at least on my 7D it does).

    - Bill

  11. #11
    Administrator Manfred M's Avatar
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    Re: Couple questions...

    Quote Originally Posted by Mike Buckley View Post
    There is one situation that I disagree, Manfred, about exposure compensation being meaningless. Assume that you have selected the ideal shutter speed and aperture for whatever look you want with regard to those two factors. However, also assume that you are using auto ISO and the resulting exposure is not what you want. You will need to adjust the exposure compensation to affect the ISO.

    Alternatively, you could shoot in fully manual mode by not using auto ISO. However, if you are switching back and forth, as an example, between using aperture priority and manual mode, you might want to leave the camera in auto ISO. That's because switching in and out of auto ISO can be more cumbersome due to having to use menu items rather than knobs or buttons on the exterior of the camera.
    Mike - checked how EC impacts what I cam doing in manual before I wrote this. I rarely use auto-ISO, so what you write makes sense. I'll have to go back and check it out.

    When I select to shoot in manual mode means I want 100% control of the camera and I will not let it make any exposure decisions for me, including playing around with the ISO value.

    EC, but the way has one advantage if you are shooting in aperture priority mode. In most cameras we can adjust aperture settings in 1/3 stop increments, but shutter speed is varied (roughly) in full stop increments only; likely a carry over from the days of fully mechanical shutters. By using EC in aperture priority mode can vary shutter speeds in 1/3 stop equivalent increments.
    Last edited by Manfred M; 4th May 2013 at 12:20 PM.

  12. #12

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    Re: Couple questions...

    Quote Originally Posted by GrumpyDiver View Post
    but shutter speed is varied (roughly) in full stop increments only
    I don't understand. I think it's reasonably customary, as an example, that you can change the shutter speed from 1/10 to 1/11, from 1/20 to 1/25, etc. Those changes are not at all close to being a difference of one full stop. There's something about your point that I'm completely missing.

  13. #13
    Administrator Manfred M's Avatar
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    Re: Couple questions...

    Mike -yes, you are right. Not sure where my head was when I wrote that. I was shooting the old film Leica the other day, and that is the way it is the way they are set, so this must have popped into my mind. The Nikons work exactly as you describe.

  14. #14
    William W's Avatar
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    Re: Couple questions...

    Quote Originally Posted by cichlid View Post
    I've ask a photography teacher in the past: "Is EC the same as changing the shutter speed to achieve the same result?" His answer was simply "Yes". So, my question to the collective is; if this is true, why is EC referred too so often? Personally, I would prefer to play with the shutter directly since EC changes it anyway. What are your thoughts?
    As has already been answered, it depends what CAMERA MODE is used as to how EXPOSURE COMPENSATION works.

    As to why one might want to use it: basically it is a matter of choice of which functionality best suits the Photographer and the Shooting Scenario.

    Some people like using Manual Mode and some like to use an Automatic Camera Mode, such as Aperture Priority Mode; Shutter Priority Mode or Program Mode. If one chooses one of the latter AUTOMATIC MODES, then the Camera’s TTL Meter governs the first choice of the exposure, therefore EC is available, to override that initial choice.

    *

    There are a few other points worth noting:

    Comment on the detailed workings of Exposure Compensation:

    It depends what Camera Brand is used. I am most familiar with modern (DSLR) Nikon and Canon – and there are differences. So when we get to fine details it’s important to specify what cameras we are discussing.

    *

    Comment on using Manual Camera Mode and Auto ISO for a Canon EOS Camera:

    Exposure Compensation would have meaning, if the function could be activated: but it CANNOT be done. In Canon DSLRs, to engage Exposure Compensation, the Power Switch moved to ¬ and then the Quick Control Dial is used for Exposure Compensation.

    However if the Camera Mode is ’Manual’, then the QCD is automatically allocated to either Aperture or Shutter Speed, whichever way the user has selected; so even if Auto ISO is available, there is no dial available for Exposure Compensation control of it.

    *

    Comment on using Manual Camera Mode (NOT with auto ISO) for a modern Nikon DSLR:
    I undersatnd that activating Exposure Compensation still has an effect (on all Nikons? - ceratinly the later ones) - as it will change the centring of the TTL meter’s readout.

    *

    Comment on Exposure Compensation and Flash and the 7D, (in fact ALL EOS DSLRs):
    Exposure Compensation cannot be set when the camera is in MANUAL MODE, (as explained above).

    Flash Exposure Compensation ‘FEC” (not “EC”) can be activated when the Camera is in Manual Mode.

    This is a two-step process first pressing the FEC button on the top and then using the QCD to select the amount of FEC. After FEC is set, the QCD returns to use it would normally have according to the Camera Mode selected: for example in Manual Mode it would control the Aperture or the Shutter Speed, as per the user’s set up.

    (Mentioned mainly because, Bill S might want to re-check the functionality and the separation and actions of FEC and EC.)


    ***


    Quote Originally Posted by cichlid View Post
    Additionally, when reading all these periodicals, it is repeated to have an f/stop of around f/8 to optimal sharpness. However, if shooting is a zoo and the subject is over 10 meters away and I'm using a 300mm lens at 100mm, the DoF is fairly large at f/5.6 and f/8. Is sharpness, in this case, a question of lens optics or DoF?
    What Manfred wrote +1.

    Additionally – (I assume you mean a zoom lens) - it’s worth noting, that if you racked that lens out to 300mm and you were around 10mtrs away from the Lion, then there would not be very much DoF at all - even at F/5.6 or F/8 and whatever format camera you were using. . . even at 200mm the DoF is getting kinda slim.

    WW

  15. #15
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    Re: Couple questions...

    I totally agree with Manfred in his excellent explanation above.

    Just to add to that or perhaps just parallel his posting..

    Using a Canon DSLR (and I suppose a Nikon or any other brand), I have control over my shutter speed and f/stop when I use Programmed, Aperture Priority or Shutter Speed Priority modes.

    I can adjust the shutter speed when shooting in Aperture Priority; adjust the aperture when using Shutter Priority and adjust either the shutter speed or aperture when shooting in Programmed Exposure Mode.

    However, with the dual dial system of the Canon (non-Rebel) DSLR cameras, the aperture and shutter speed are very easy to shift because one dial controls the aperture whle the other controls the shutter speed. This may or may not be true with other brands. I am pretty sure this is not true with the Canon Rebels (although I have not shot a Rebel in ten years or more...

    What I cannot do in any of these modes is to increase or decrease the total exposure for any shot. The f/stop and shutter speeds are interconnected so that when one is modified the other is also modified to maintain the same exposure.

    If you want or need to increase or decrease the total exposure for an image, that is when Exposure Compensation comes into play (when using any of the auto or semi auto modes). It allows you to increase or decrease the total exposure for any shot (auto exposure bracketing also does this).

    I don't shoot in Auto ISO, so I won't relate to that system...

    A standard practice among many professional photographers of the past when shooting slide film was to bracket exposures to ensure that they had one shot with optimum exposure. This was really of prime importance when shooting the original Kodachrome which had an ASA (same as ISO) of 10 with virtually no exposure latitude leeway. Most non-professionals never used this technique simply because it was too darned expensive. Film and processing cost money and cutting down your acceptable imagery by 2/3 was too expensive unless you had an unlimited film budget like many National Geographic Magazine photographers worked with.

    However, a photojournalist friend of mine, who always bracketed his exposures, got a message from the Naval Photographic Center (during the Vietnam conflict) which read: Do you know that 2/3 of your imagery you send us is either over or under exposed. He replied, "No kidding, that is really interesting. I'll have to check my cameras!"

    Todays DSLR cameras make bracketing exposures very simple and it costs nothing extra. The Canon DSLR cameras (I don't know about other brands) will shoot a burst of three bracketed exposures and then stop until the next time you press the shutter button. The only downsides might be the extra memory needed (I have more than enough memory) and the extra imagery you need to look through in post-processing. Another downside is that it is not feasible when you are shooting action in a burst mode Remember, it will shoot three shots at varied exposures and then stop!.

    The advantages are that you will almost always have one absolutely perfectly exposed image even in chancy lighting situations and that you often will have a sequence you can use for an HDRI composite. I have noticed that when shooting AEB in high speed burst mode, the shots are close enough in framing that you can usually do a decent HDR image even without using a tripod. This is especially true since I am often shooting with a monopod.

    BTW: On a Canon camera (don't know about the other brands) you can combine Auto Exposure Bracketing (AEB) with Exposure Compensation (EC). This can come in handy when shooting night shots if you start off using one of the semi auto exposure modes (AV, TV or P) with a one stop AEB and a minus one stop EC. This will give you one shot as the meter reads, one shot at 1-stop below the reading and one shot at 2-stops below the meter reading. I can almost guarantee that one of these exposures will get you very close to optimum exposure. Most night shots suffer from over rather than under exposure.

    I always have one of the three User Selected modes of my Canon 7D set up this way and a second User Selected mode set up for manual exposure. NOTE: IMO, having three User Selected Modes available is quite a luxury, matched only by the 40D in 1.6x cameras. The 50D has two User Selected Modes and the 60D is restricted to a single User Selected Mode.

    The three shot AEB burst with a -1 EC will definitely get me very close to the optimum exposure and I will then work from there using manual controls.
    Last edited by rpcrowe; 12th May 2013 at 02:35 PM.

  16. #16
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    Re: Couple questions...

    Hi All,

    Just speaking about the EC many photographers suggest to use 18% Gray card to attain the perfect/accurate Exposure when Camera is on Manual mode.

    Could someone please illustrate how 18% Gray card play the role to attain the correct exposure in Manual mode??

  17. #17
    William W's Avatar
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    Re: Couple questions...

    Quote Originally Posted by muralimithun View Post
    many photographers suggest to use 18% Gray card to attain the perfect/accurate Exposure when Camera is on Manual mode. Could someone please illustrate how 18% Gray card play the role to attain the correct exposure in Manual mode??
    Post #15 in this thread specifically. - the bottom of that post describes what you are asking with an image example - here it is revisted for you:

    You can also meter from a Photographic Grey card, too.

    Couple questions...

    If you use a reference material (for example a grey card), for your exposure reading then you must ensure that the reference material is in the SAME LIGHT and facing the SAME DIRECTION as the Subject that you wish to photograph.

    For example, in the image above, the Photographer is making a light meter reading and the Subject will be standing in the shade, where the Grey card is located. Thus if there is any sunlit background in his shot, it will be blown out as per the sample image posted.


    *


    The thread generally will provide enormous benefit I expect. I suggest you read through the whole of that thread

    *

    To be clear: I do NOT use a grey card to attain the CORRECT exposure per se - I.E. the grey card reading will NOT necessarily be the exposure that I will use. I use a Photographic Grey Card to indicate what the ‘correct’ exposure is for that particular lighting and then I make the picture of the subject in that lighting exposing the scene the way I want it.

    Also – from a more (pedantic) technical perspective 18% Grey is not to what DSLR’s Light Meters’ middles are set – more like 12% Grey. So I factor that (about a ⅓Stop) into the equation, also.

    That is to say, if one meters a scene using a Photographic Grey Card – then stop down ⅓Stop from the reading given.

    ***

    I use my Photographic Grey Cards to set White Balance, more often than I use them for Exposure Referencing.

    A (quality) Photographic Grey Card in good condition, is more accurate for White Balance Referencing than random pieces of "white", like handkerchiefs, table napkins or white paper.

    Many Camera User Manuals go to the trouble of mentioning this fact - but the sentence is usually hidden somewhere in the footnotes - go figure?

    A Photographic Grey Card included the first frame of any Same Lighting Set of images, is the other use I have for my Grey cards – for most accurate PP & P (Post Production and Printing) of that set of images.

    WW

  18. #18
    muralimithun's Avatar
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    Re: Couple questions...

    Quote Originally Posted by William W View Post
    Post #15 in this thread specifically. - the bottom of that post describes what you are asking with an image example - here it is revisted for you:
    Bill,

    I went through the whole thread, Thanks for the very useful and Illustrated post

    Agree with You Exposure depends upon the different lighting conditions and the subject.

  19. #19
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    Re: Couple questions...

    Basically, IMO, metering off a gray-card for still photography, sort of transforms the functioning of your reflected camera meter into something like an incident light meter.

    What I mean by this is that you need to adjust your exposure differently when metering the scene or subject as opposed to when metering off of a gray card.

    When metering a scene or subject, the camera's meter tries to convert everything to gray. Therefore if you are shooting a snow scene, you need to add extra exposure to make the snow white, not gray. When shooting the proverbial black cat in a coal bin, you need to decrease exposure so the cat and the coal will be black - not gray.

    However, if you meter off a gray card; you need to subtract exposure when shooting a bright scene (like the snow) and add exposure when shooting the black cat in the bin.

    Exposing for video is a completely different game and is not within the context of this reply...

    Actually for most white balance referencing, I will use a WhiBal card which Donald put me on to. It works quite well. I don't know if the less expensive eBay white balance cards would work equally as well. I do know that I often use the white coats of my dogs as my white balnce target. That works great since the dog is always my main subject and I want its coat to be white in the image...

    Scott Kelby includes a white balance target in some of his Photoshop books. That works quite well but, being of paper stock, it is not as rugged as the WhiBal card. I hated the idea of spending money on the WhiBal target but, I am happy that I followed Donald's recommendations. I have the larger card and am considering the purchase of the smaller model for my upcoming Venice, Greece and Istanbul trip. Or, I might just cut down the Scott kelby target into smaller squares to save money. That just might be my Scottish heritage filtering through...
    Last edited by rpcrowe; 8th May 2013 at 04:25 PM.

  20. #20

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    Re: Couple questions...

    To Everyone,

    Thank you for your postings to my inquiry.
    Much does make more sense now.

    Erik

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