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Thread: Lens filters for Contax 645 system?

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    Lens filters for Contax 645 system?

    Having read here and other places about the problems of correcting the white balance in the RAW developer, for example correcting a tungsten cast by boosting the blue channel, and the resulting noise in the relevant channel, I am leaning towards using filters on my lenses to get the white balance approximately right, and then only making minor adjustments in post.

    I have the Contax 645 35, 80 and 120 lenses, as well as a Hartblei 45, and so I am looking for a system of filters which I could reuse between these lenses. Does anyone have any experience in this area, and could recommend something?

    I presume that since the purpose is to pre-correct the lighting, and not the lens cast or other factors, that the regular white shading files would be used, and not special ones matched to the filters?

    Thanks in advance.
    Carsten - Website

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    Re: Lens filters for Contax 645 system?

    Carsten not sure why you would even bother. Just get a whibal card or a color checker in a lighting situation take a shot under that lighting and in your software package take a white balance reading off that frame and apply to the rest of your images. Or you can do the same thing with LCC calibration tools , put a translucent card over the lens open up a little take a shot and do the same thing in your software package. Frankly most times i do neither with my Phase back just put it on daylight and go to town and shoot and maybe fine tune in C1 a little. Not sure about other backs but my Phase back is rarely off more than 200 kelvin. Now if your lenses from the Contax are bending towards yellow than even so you can just correct that with your WB tool in the field under changing light. Or you can just make profiles for each lens with the LCC tool and apply under that particular lighting. Using filters on the lens may work in certain situations with regards to lighting say daylight but may radically change it under tungsten and make it even more a issue to correct later.
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    Re: Lens filters for Contax 645 system?

    LCC calibration card 18 dollars. I carry one with me

    http://www.captureintegration.com/so...aturedproduct/
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    Re: Lens filters for Contax 645 system?

    That is the standard workflow, yes. However, indoor shots often have noise in the blue channel, but I don't believe that there is anything inherently noisy about blue light, but rather that the tungsten yellowish light requires a boost in blue to correct, and it is this boost which causes the noise. There are comments here and there which indicate as much. I am really surprised that no one takes this to its logical conclusion, and start using filters to get better quality light going to the sensor, and hence lower noise. I will try it, but I don't have a back yet. I could try with my M8, to verify that it works as expected.

    Guy, if you still have any blue filters lying around, trying taking an indoor tungsten-lit shot with a blue filter, and then whitebalance, and compare that to your normal workflow. There should be an improvement, since the boost to blue comes without boosting individual channels (which is the same as pushing, or underexposing and then brightening), just like film days.
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    Re: Lens filters for Contax 645 system?

    Quote Originally Posted by carstenw View Post
    That is the standard workflow, yes. However, indoor shots often have noise in the blue channel, but I don't believe that there is anything inherently noisy about blue light, but rather that the tungsten yellowish light requires a boost in blue to correct, and it is this boost which causes the noise. There are comments here and there which indicate as much. I am really surprised that no one takes this to its logical conclusion, and start using filters to get better quality light going to the sensor, and hence lower noise. I will try it, but I don't have a back yet. I could try with my M8, to verify that it works as expected.

    Guy, if you still have any blue filters lying around, trying taking an indoor tungsten-lit shot with a blue filter, and then whitebalance, and compare that to your normal workflow. There should be an improvement, since the boost to blue comes without boosting individual channels (which is the same as pushing, or underexposing and then brightening), just like film days.
    I get that all the time while shooting weddings. I just lower the saturation of the yellow rather than boosting the blue channel. If detail is lost in the light areas you can restore it with the yellow luminance slider. Then final tweak with WB. Little to no noise added that way. Easy to batch similar shots that way also. Give it a try.

    Not all soultions need be complex : -)

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    Re: Lens filters for Contax 645 system?

    Thanks Marc I was trying to answer this and had a nice post and bam internet went down.

    My comment was sort of the same vein that using the filters is more a PITA than what you can just make certain adjustments for in the software. Maybe Doug and others can add to this also.
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    Re: Lens filters for Contax 645 system?

    Marc, if you lower yellow, you lower the exposure. To compensate you would need to pull it up again... I will try it and see what I get. Maybe it is not worth it, but if I pay all this money for higher image quality, using a filter doesn't seem like a big deal.
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    Re: Lens filters for Contax 645 system?

    I'm not sure what your shooting situation is, Carsten, (i.e. changing light, mixed, etc.), but I have had very good results with using a custom white balance setting for indoor work. I'm not speaking of weddings where the light is changing as the subject moves throughout the environment, etc., but for more or less constant tungsten or fluorescent environs.

    With my Phase back I simply shoot a white card to set the custom WB and every shot is very, very close to the desired outcome. This is also good with mixed light where artificial light is combined with daylight filtering in. Is this an option for your application?

    (Shooting a white card rather than a gray card works better for my particular indoor setting.)

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    Re: Lens filters for Contax 645 system?

    Interesting. So, you are saying that setting the white balance in the back before shooting yields better quality than performing the white balance on the computer later? In other words, looking at the red, green and blue channels separately, the blue channel isn't noisier than the other two? That makes me wonder what is going on in the back in this situation.

    I am looking at indoor photography in fixed, natural, or mixed light, and no possibility of balancing the light from my side with strobes, etc. Setting white balance is an option, as are filters, and any other similar workflow, but not manipulating the situation itself. At least, not for now.
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    Re: Lens filters for Contax 645 system?

    Cartsten, I'm just saying that for tungsten or fluorescent scenes I get accurate results (i.e. less required adjustments in post) when I go to the trouble of using a custom WB setting. I have not seen a difference in results when I do make the adjustments in post, other than it requires more effort. If a color-checker is used (in the first shot) it works about the same, but I do like setting custom white balance to save some work later.

    As for noise, I have not seen a difference, and normally see more noise in the blue channel of any of my cameras. I find that underexposure is the biggest problem so concern myself with getting the shadows well exposed (at least trying to do so). This can mean flattening the lighting a bit at times (flagging) to avoid highlight clipping. Mostly, I've not seen much of a problem with noise in general but I shoot mostly on low ISO settings.

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    Re: Lens filters for Contax 645 system?

    You received good answers so far, but if you still want filter/filter system suggestions, I used to use (and still do for some occasions but for different reasons) the Cokin P system. Get one or two step up rings and you're good to go with all your lenses. Over the years I've amassed quite a collection, don't use most anymore. One thing to consider however is that you'll be putting yet another piece of glass in front of your lens that may get dirty, etc. Plus, you're blocking light so will have to boost your exposure either way.

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    Re: Lens filters for Contax 645 system?

    Quote Originally Posted by carstenw View Post
    Marc, if you lower yellow, you lower the exposure. To compensate you would need to pull it up again... I will try it and see what I get. Maybe it is not worth it, but if I pay all this money for higher image quality, using a filter doesn't seem like a big deal.
    Carsten: Keep in mind that if you use an external CC filter, you also cut the amount of light hitting the sensor () and hence you also have to increase exposure to compensate too --- which is something you can easily do regardless, if you choose Marc's method.

    At the end of the day, using external filters to color correct a digital sensor does not buy you much of anything over doing the same thing digitally/internally, and thus why most of us no longer use CC filters... Since we're on the subject, I'll add I only carry the CI LCC white sheet and two filters nowadays; a 3-stop ND and a polarizer. And I cannot tell you the last time I even pulled the polarizer to look at it, let alone use it, so time for it to go away too.

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    Re: Lens filters for Contax 645 system?

    I can't count the number of times I've pointed this out here on this forum :-). Guess someone listened!

    The stronger the cast of light the more the effective "push" of the underexposed channel. With a Phase One back (which is what I know best) you can push any given channel several stops from the base ISO with no visible noise. So shooting without a CC filter will only result in noticeable noise if:
    1) the overall image is pretty underexposed
    2) the ISO of the shot is high
    3) the color cast is extreme (e.g. blue-gelled stage lighting)
    Any of these three situations would result in an extreme push for the disproportionally underexposed channel which will result in noise in the blue channel. Because Capture One has really great color noise reduction the end result would be some loss of detail in shadows rather than the tale-tell low-frequency blue noise that you see in dSLR files in a similar situation.

    So while in theory correcting the light entering them camera will always result in better IQ the difference is negligible for digital backs except in the three situations above.

    With a dSLR the importance of correcting the light entering the camera is magnified because of their smaller dynamic range and bit depth. For dSLRs it might be worth the while even at base ISO even with a properly exposed image.

    Also keep in mind that filtering the light entering the camera inherently cuts down on the absolute amount of light entering the camera, sometimes drastically (the balance of light is achieved by blocking the over-prevalent color of light). So this is best reserved for situations with lots of light or when using a tripod.

    You would use the color-effects filter then if you wanted to add additional light in the scene with a flash/strobe. You match the strobe's color to the scenes color so the scene only contains one temperature of light, then you correct the light entering the lens so the sensor sees a daylight-balanced (even RGB) spectrum of light where detail can be captured in each channel by the limited DR sensor of a dSLR. Then in post if you want to warm or cool the scene you can do so without losing IQ because each channel contains detail throughout the DR.

    By the way, in a tough lighting situation a dSLR with perfect workflow and filters still won't match the final IQ of a MFDB with a standard workflow and no filters, so this advice is mostly for dSLR users, or for use in extremely cast light, or for MFDB owners who are unusually anal about getting every last drop of IQ.

    Doug Peterson, Head of Technical Services
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    Re: Lens filters for Contax 645 system?

    You aren't lowering the exposure by lowering the saturation ... just the intensity of the yellow cast. As you know, when you white balance a seemingly correct exposure that's too yellow, it suddenly is underexposed looking.

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    Re: Lens filters for Contax 645 system?

    Yes I have the Polarizer and ND filter myself but I RARELY use the polarizer in Arizona. You can see why here. Like I really need it. LOL
    Photography is all about experimentation and without it you will never learn art.

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    Re: Lens filters for Contax 645 system?

    Quote Originally Posted by Jack Flesher View Post
    And I cannot tell you the last time I even pulled the polarizer to look at it, let alone use it, so time for it to go away too.
    I still use the polarizer to reduce unwanted glare or reflections on water. I'm pretty sure I would miss it if I removed it from my kit.

    That said, like you, Jack, the ND filter is the only other filter in my bag (including a grad sometimes). Oh, and I often carry a couple of UV/haze or other protectors at the ocean in case I shoot too close to spray (as I tend to do).

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    Re: Lens filters for Contax 645 system?

    Quote Originally Posted by Jack Flesher View Post
    Carsten: Keep in mind that if you use an external CC filter, you also cut the amount of light hitting the sensor () and hence you also have to increase exposure to compensate too --- which is something you can easily do regardless, if you choose Marc's method.
    Yes, but the light that does reach the sensor through a filter is 1) closer to correctly colour-balanced, and 2) correctly exposed. If you do it in post, the blue channel is underexposed and will have to be pushed in post, boosting the noise. Since I am talking about dim situations, and since there is least information in the shadows, this could (in theory) cause the blue noise to increase. I will try it with my M8 tonight, and with my back one day when I have it, and see how much of a difference it makes.


    Quote Originally Posted by dougpetersonci View Post
    I can't count the number of times I've pointed this out here on this forum :-). Guess someone listened!
    Yes.

    3) the color cast is extreme (e.g. blue-gelled stage lighting)
    Tungsten lighting is not as extreme as gels, clearly, but the cast is not exactly subtle either.


    Also keep in mind that filtering the light entering the camera inherently cuts down on the absolute amount of light entering the camera, sometimes drastically (the balance of light is achieved by blocking the over-prevalent color of light). So this is best reserved for situations with lots of light or when using a tripod.
    In these situations I would be on a tripod anyway, so the question is if the exposure would be pushed beyond the 32s of the e54LV. I doubt it, but I might hit it in extreme situations.


    Quote Originally Posted by fotografz View Post
    You aren't lowering the exposure by lowering the saturation ... just the intensity of the yellow cast. As you know, when you white balance a seemingly correct exposure that's too yellow, it suddenly is underexposed looking.
    Yes, that is what I meant: the apparent exposure. By reducing the yellow (green+red), you would have to tweak the exposure slider to compensate, adding more noise to the other channels (blue). Same thing, different words.
    Carsten - Website

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