hector_evans Posted April 10, 2008 Share Posted April 10, 2008 I noticed than when I shoot in bright sunlight the blue sky looks grey in my shots. I cannot fully fix this in Digital Photo Professional. I suspect that this has to do with the small apertures (f18-f22) I use in bright sunlight conditions. Any suggestions on how to get the correct colors? I have a Rebel XTi, using manual mode. thanks Link to comment Share on other sites More sharing options...
bueh Posted April 10, 2008 Share Posted April 10, 2008 Example or it didn't happen! You don't mean overexposure, do you? Link to comment Share on other sites More sharing options...
simus Posted April 10, 2008 Share Posted April 10, 2008 Hector, Could you post a sample image? Antonio Link to comment Share on other sites More sharing options...
photo_dark Posted April 10, 2008 Share Posted April 10, 2008 white-grey or just grey? If you are shooting in the general direction of the sun on a clear day, unless the sky is bullet blue, it's likely you are overexposing the sky. Especially if there is any pollution or haze (not that we have any of that in north america). A polarizer can help quite a bit (only at certain angles to the sun), but you will likely just have to either shoot with the sun at your side/back, or underexpose the foreground to make up for it. Fill flash helps for closer subjects, a neutral gradient filter works great for landscapes to dial down the sky a few notches. Remember, a digital camera doesn't have the same dynamic range that your eyes do... so when you are shooting something that is in shadow on a bright day will render everything that isn't in shadow, well overexposed. Also, you are going to be better off shooting at f8 or f11 max. There is no advantage to ultra high apertures on a crop sensor (you don't gain any sharpness) and you introduce some pretty substantial diffraction problems that can soften the center substantially. In bright sunlight, try shooting at f/11, ISO 100 and 1/250. Try using a polarizer, and do your best to position yourself so you arn't shooting directly into the sun. Link to comment Share on other sites More sharing options...
peter_mckone Posted April 10, 2008 Share Posted April 10, 2008 It's hard for a camera to expose for shaded foliage and bright sunlight at the same time. Lower the exposure compensation to -2/3 and take the picture again. Then use Photo Shop to get the photo you want. Link to comment Share on other sites More sharing options...
g dan mitchell Posted April 10, 2008 Share Posted April 10, 2008 Just an aside - generally avoid those small f/18-f/22 apertures on your crop sensor camera. You are compromising the potential sharpness of your images by introducing diffraction blur. Unless you have a very good reason in a particular shot for using a smaller aperture, stick to about f/8 or larger. And do share a sample or two of your problem shots so that we can more effectively offer advice. Dan Link to comment Share on other sites More sharing options...
trebor_navilluso Posted April 10, 2008 Share Posted April 10, 2008 One more approach, if this is a controlled shot, would be to make two exposures. One for the sky and one for the foreground. And blend them in photoshop later. But obviously this can't work with action photos, only scenics. Underexposing, tweaking later, and fill flash can all help. But for extreame cases, your best bet is slow colornegative film, which is why I kept my EOS 1 and keep it handy. Link to comment Share on other sites More sharing options...
john_bellenis Posted April 10, 2008 Share Posted April 10, 2008 If you are shooting with a crop sensor body at those apertures you will definitely be seeing the effects of diffraction (loss of fine detail, lack of sharpness). I am guessing you are exposing for a dark foreground and the sky is getting blown out. A polarizer could help depending on the angle of the sun, or a graduated or split ND filter may be the answer. Posting an image would definitely help people give you relevant advice though. Link to comment Share on other sites More sharing options...
zml Posted April 10, 2008 Share Posted April 10, 2008 <i>If you are shooting with a crop sensor body at those apertures you will definitely be seeing the effects of diffraction (loss of fine detail, lack of sharpness). </i> <br><br>That thing again..? In real life - pictures of resolution charts excluded - you are losing more detail and sharpness due to poor technique (both shooting and post-processing) than due to lens diffraction (or the diffraction-limited sensors, whichever way you prefer to nitpick.) Link to comment Share on other sites More sharing options...
chrisjb Posted April 10, 2008 Share Posted April 10, 2008 Most has been said, sun behind reflects blue in sky, stick around f8 etc. here`s a simple tutorial to help fix pics that you want more blue in the skies http://www.myjanee.com/tuts/adjlay/adjlay.htm have fun :) Link to comment Share on other sites More sharing options...
john_bellenis Posted April 10, 2008 Share Posted April 10, 2008 "That thing" is very real, very noticeable, and if your technique and post processing are worse than bad diffraction then there are some real issues. I would advise reading this tutorial to understand the physics, and look closely at the fabric sample illustrated to see the very real effects. http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm# Many overzealous photographers looking for ultimate depth of field, have ended up with distinctly fuzzy shots, purely through stopping down too far for the format. Seriously, this is a "real life" issue and at f22 on a 1.6X crop camera you WILL see it - and yes, that IS poor technique. Link to comment Share on other sites More sharing options...
zml Posted April 10, 2008 Share Posted April 10, 2008 <i>that IS poor technique.</i><br><br>No, that is pixel-peeping. <br>You'd be hard pressed to detect any artifacts of diffraction in most real life pictures taken above the "theoretical" threshold of diffraction-limitation of a given sensor (say, above f/9-10 for a 1.6 crop.)<br> And yes, I'm very familiar with the science behind diffraction and am not denying it; I'am merely stating that diffraction is like bacteria: it's there, but hard to actually see without unnatural devices. Link to comment Share on other sites More sharing options...
john_bellenis Posted April 10, 2008 Share Posted April 10, 2008 I have seen the effects of diffraction in medium format and even 4x5 Polaroids of studio shots, and had to subsequently back off on the aperture to retain detail - with my own eyes no less, no "unnatural devices" required... I'm not sure when it became "in vogue" to deny real visible optical issues that have been seen, understood and properly avoided for decades. Personally I am not one to champion poor techniques or to proudly claim that other poor techniques will mask the effects of diffraction as in... "In real life - pictures of resolution charts excluded - you are losing more detail and sharpness due to poor technique (both shooting and post-processing) than due to lens diffraction " Each to his own I guess... Link to comment Share on other sites More sharing options...
g dan mitchell Posted April 10, 2008 Share Posted April 10, 2008 Regarding diffraction... I'll agree that you would be hard pressed to see any difference in a print made from a crop sensor camera between a photograph at f/8 and one at "f/9-10." But our OP was shooting at f/18-22. At those apertures you may not notice much difference in drug store sized prints, but the loss of fine detail will be noticeable in larger prints. In any case, unless there is some alternate benefit to shooting at such small apertures (e.g. - a photo of a foggy scene in which you want really huge DOF) there is no good reason to shoot at such small apertures on a 1.6x crop body. Dan Link to comment Share on other sites More sharing options...
mark u Posted April 11, 2008 Share Posted April 11, 2008 A circular polarising filter may be helpful. A clear sky should look blue if the sun is behind you. If it doesn't, then you are overexposing. However, when the sun is to your right or left you can eliminate the reflections of tiny particles in the atmosphere that wash out the sky colour by using the filter. Better CP filters have a mark on the filter ring, which should be aimed at the sun for maximum effect. Link to comment Share on other sites More sharing options...
hector_evans Posted April 11, 2008 Author Share Posted April 11, 2008 Sample1<div></div> Link to comment Share on other sites More sharing options...
hector_evans Posted April 11, 2008 Author Share Posted April 11, 2008 I am attaching 2 samples to show the problem. My theory about small apertures seems to be wrong because these samples were shot at around f11. My attempt to fix the problem by playing with white balance and saturation was unsuccessful. Thanks for all the replies. Link to comment Share on other sites More sharing options...
dcheung Posted April 11, 2008 Share Posted April 11, 2008 Michael Liczbanski >> You seem to be mis-informed in terms of diffraction or at least your comments goes to show that you have not done any serious experimentation with small apertures and prints. Diffraction is a serious limitation. I'm not even gonna bother arguing with you. You should maybe hit a few google searches on the topic and do some real life experiments before you come on there and tell people that diffraction limit is only for pixel peepers. I've had many images ruined back in the days when I didn't know about diffraction limitations. I don't want to see that happen to others. Link to comment Share on other sites More sharing options...
photo_dark Posted April 11, 2008 Share Posted April 11, 2008 One thing to note regarding crop sensors.... Diffraction starts to become an issue above f/16 on full frame sensors, while it starts to show up above f9/10 on crop sensors. So unless you are doing macro work, the rule of thumb is f/11 max on crop sensors, f/16 max on full frame. I've also heard that the 'limit' is partially governed by the megapixel-sensor size ratio... ie.... an 8.2mp 1.6x camera will have a higher tolerence than a 10.2mp 1.6x camera. This is why the 12.2 MP 5D has a much higher tolerance (f/16) than a 10.2mp 40D with a 1.6x crop sensor. Someone feel free to correct me if i'm wrong on this, i'm only repeating what i've read elsewhere. Link to comment Share on other sites More sharing options...
photo_dark Posted April 11, 2008 Share Posted April 11, 2008 The first picture looks rather underexposed and quite hazy, the second looks to have better exposure, but is quite dull... A polarizer would help here no doubt, as well as turning on the histogram on your camera (hit the info button beside the LCD). If it is all bunched up left of center, then the picture will be underexposed, rendering blue skies more of a dark grey. Kind of the same way over-exposing will render blue skies white or greyish-white. Anyone else have any advice here? Link to comment Share on other sites More sharing options...
zml Posted April 11, 2008 Share Posted April 11, 2008 <i> I've had many images ruined back in the days when I didn't know about diffraction limitations. I don't want to see that happen to others.</i><br><br>Well, I strongly suspect that among many ways to ruin one's - including yours - images, diffraction plays but a minor part... Link to comment Share on other sites More sharing options...
chrisjb Posted April 11, 2008 Share Posted April 11, 2008 Hector, your exposures are off, try bracketing the exposures 2 each side 1/2 stops to get a closer exp. While not tryin to take sides my take is. with film small apertures caused problems with colour depth. with 3 layers of emultion plus base layer adaquat light was needed to saturate the colour layers evenly. by using small f stops this pulled the light short of the lower and base levels, lowered colour rendition and contrast.Varying with different types of film & emultions as well as the d&p. Now with digital all the lil optic lenses need an even amount of light. therefore a small aperture will pinpoint the center of the sensor but rob the edges of light causing larger falloffs and degraded image Enhancing the appearance of deffraction. anyway sounds like good BS. I get better results staying under f11 even with my Hassy gear :) Link to comment Share on other sites More sharing options...
savas_kyprianides Posted April 11, 2008 Share Posted April 11, 2008 Blue skies look gray sounds like a sad country western tune. Link to comment Share on other sites More sharing options...
dcheung Posted April 15, 2008 Share Posted April 15, 2008 Michael Liczbanski >> "Well, I strongly suspect that among many ways to ruin one's - including yours - images, diffraction plays but a minor part..." No, these photos I'm thinking of were technically perfect except for the diffraction problem from being at f/16-22. Like I said, it's a real problem that I didn't know about back then. If you try to sell it off to shooters as being a lab-only-non-real-life phenomenon and people believe you, then you'll end up with people trying to increase depth of field (or even sharpness from using only the center of the lens elements) and end up with diffraction problems. Link to comment Share on other sites More sharing options...
hector_evans Posted April 16, 2008 Author Share Posted April 16, 2008 I think I found the answer to my own question. Page 53 of Rebel XTi/400D user's manual says:<br><br> <b>>>> High temperatures, high ISO speeds, or long exposures may cause irregular colors in the image.</b><br><br> In my case the temperature is always high when I get these strange colors. Case closed? Link to comment Share on other sites More sharing options...
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