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Thread: pushing, exposure compensation ect ect

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    Subscriber Member mwalker's Avatar
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    pushing, exposure compensation ect ect

    I just read the article in LFI on the Ektar 100. They mentioned exposure compensation of +1/3 to +1/2. It sounded interesting I may try some.
    Is it best to make the exposure compensation on the camera or make it in digital post; PS/LR?
    When you "push" the film thats done in lab processing, again can you push digitally? I maybe way off base here
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    Re: pushing, exposure compensation ect ect

    When you push an analog film, you need to tell the lab (unless you are doing it yourself). They will process it longer -- this will bring up the exposure, but create more grain and contrast. Once you scan it, it will be treated like any other piece of film. So you can do basically anything you have done with all the other film you have digitally post processed. That said, due to the fact that it starts out with more contrast and more grain, any efforts to boost exposure after the fact will be more difficult. In some cases, you will also be adding more grain from the CCD in the scanner being pushed. Over worked film scans tend to look flat, grainy with a very compressed tonal range. I.E. Like ****e.
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    Subscriber Member mwalker's Avatar
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    Re: pushing, exposure compensation ect ect

    Thanks Stuart, I've got to get my mind wraped around the analog to digital workflow..this is new to me.

    One other question....is it better to shoot BW film or something like the new color slide film Ektar 100 and then convert to BW in CS3
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    Re: pushing, exposure compensation ect ect

    No problem Mike -- it takes a lot of practice to begin to figure it all out. In any case, I find it is much better to shoot black and white film and scan it in -- color slide looks great in color, but it has a much smaller tonal range, higher contrast and in general it is harder for the scanner to deal with (in most cases)...it also has a different grain structure. If you just scan regular black and white film, you will have a much longer tonal range, more exposure flexibility and usually a more pleasing grain structure.
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    Re: pushing, exposure compensation ect ect

    You will also tend to find that high contrast films like say Velvia 50 are a **** to scan - requiring experimentation with various scanning software packages - NikonScan vs Vuescan vs Silverfast, etc. A lot of scanners have trouble handling the contrast range.

    One of the best films I found for an amazing, detailed yet simple scan was 160NC using the in-box Nikon software (on a 5000 ED with multi-sampling). Other films 'responded better' to SilverFast or Vuescan.

    Lots of C41 and E6 films to play with. On average, you tend to get more detail from slide film, but ultimate detail is sometimes not what you're looking for.

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    Re: pushing, exposure compensation ect ect

    Are you using the 160NC to scan and convert to B&W or keeping the color? I like the idea of shooting in color and converting to BW if the image warrants but keeping the flexibility of color.
    I have a Nikon 5000 ED.

    Stuart, Do you have a favorite BW film that scans well?
    Last edited by mwalker; 3rd December 2008 at 11:43.
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    Re: pushing, exposure compensation ect ect

    I like the fuji black and white films, particularly Acros. If you don't really care about longevity, will never enter a darkroom and don't want to process yourself, the C41 black and white films like BW400CN and XP2 are great for scanning. If you want to shoot color negative and convert to black and white, you are much better off just shooting digital and not bothering with scanning at all. True black and white films look the best for black and white.
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    Re: pushing, exposure compensation ect ect

    Quote Originally Posted by Stuart Richardson View Post
    I like the fuji black and white films, particularly Acros. If you don't really care about longevity, will never enter a darkroom and don't want to process yourself, the C41 black and white films like BW400CN and XP2 are great for scanning. If you want to shoot color negative and convert to black and white, you are much better off just shooting digital and not bothering with scanning at all. True black and white films look the best for black and white.
    Good to know...I'll just shoot BW film.

    I have a good local lab...they process by hand. I'm thinking Fuji Acros 100; Adox CMS20, Adotech 24+1; Efke 25, Rodinal to start. I can take the film and bottles of developer to the lab....5 min from my house!!
    Last edited by mwalker; 3rd December 2008 at 13:40.
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    Re: pushing, exposure compensation ect ect

    BW400 and XP2 are nice. I was keeping the 160 color with some B&W conversions.

    With the limited experimentation I did scanning B&W films vs B&W conversion, I didn't find a B&W film that gave me the balance of fine grain vs. B&W tonality (vs over-the-top contrast some gave) that I was willing to say I'd fallen in love with. For grainy high-contrast shots, you could pick you poison.

    However, there were a lot of B&W films I'd yet to try before I decided to stay all digital. That said, a keep trying to resist a nice M7 and 2 lens kit ;>

    Unfortunately in my neck of the woods, anything but main stream films need to be shipped-in ordering and getting the local 'shops' (I say that loosely) to do B&W processing is like pulling teeth. As for a darkroom - barring a home reno, she ain't happening.

    Getting the combination of films, scanner and scanning software and technique that delivers the results you like takes time, patience and a lot of practice, but it can be very rewarding.

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    Re: pushing, exposure compensation ect ect

    My exposure technique, when not shooting in some auto mode, for some time now has been to measure the "toe speed". This is the minimum exposure needed to get any density on film, above fogging speed. It does vary somewhat with developer, time, temperature, but works for both B&W and color, or even digital. For TMX in XTOL (no matter dilution) I use 320. This means I set my spot meter to 320 and measure the darkest place I want texture - and this is my exposure.

    I then develop a fixed time in stock XTOL for minimal grain, and adjust the scanner to pick up the full scale. With my Imacon I do this pretty much by increasing the ADC gain and using the ADC offset to eliminate the base fog - these are indirectly tweaked using the black/white points. I find this produces better results than increasing development to obtain full density in the highlights and then scanning. For printing the latter is superior, but I find increasing gain and tonality during scanning provides a more pleasing appearance. This is to my taste, and highly dependent on my subjects and equipment, so not suggesting anyone mimic it.

    I also shoot other films, but go about it the same. For color negative film I like to give it a few extra stops since it often gets a little grotty in the thin parts, and the ones I use have latitude to spare. The labeled speed usually goes right on the spot meter and I then meter for the darkest texture.

    Anyway, works for me.

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    Re: pushing, exposure compensation ect ect

    Can you explain what you mean by ADC gain on the Imacon? The only problem I have had with the Imacon is that sometimes I have rather thin negs, and the black points are fully pushed up against left side of the histogram. Adaptive light only blows them more...I do now know of a way to DECREASE the amount of light or shorten the exposure...
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    Re: pushing, exposure compensation ect ect

    The Imacons (like just about every scanner) have an trilinear CCD. This means there's one line each for the primaries, in this case R-G-B. The film is stepped underneath the scan head, and for each step each line is read out. The channels are shifted to combine back into proper RGB before further processing. Each line is clocked out separately, with a different output port. Each of these ports feeds into an ADC; one for each channel.

    The first thing that happens to the analog output from the CCD when it gets to the ADC is it goes to an input amplifier. This allows the ADC to have high input impedance, clean up the signal, tweak it suit the quantization (like adjust voltage levels prior to the hold stage where it's locked for the quantization), and so on. Just about all ADCs designed for quality image capture have programmable input amplifiers, using two parameters: offset and gain. The offset is subtracted from the analog signal during amplification, and the gain, well, adjusts the amplifier gain - its multiplier.

    If you imagine a histogram captured without offset, that's slightly shifted to the right, then recapturing it with the offset(s) properly set up will shift it to the left. Since there is one ADC per channel the offset(s) specify the black point. (White point for negs.)

    If the histogram doesn't extend all the way to the right, then an increase in gain will push it out. Similarly, if it's extending past the end (i.e. it's clipped), then reducing the gain will pull it back in. In other words, this determines the white point (black point for negs). These two points are very similar to how you would adjust them using the levels tool in Photoshop - the transformation is trivial. They can be used for instance to eliminate the C41 orange mask.

    Since most noise during a scan, apart from film grain, occurs during hold and quantization, rather than in the transfer from CCD well to ADC or during input signal conditioning, getting the black and white points correct here is a very good idea. Adjusting the black and white points post capture multiplies the quantization noise by the gain factor, and anything that stretches the histogram will need to apply a gain.

    When you set the white and black points on the Imacon it adjusts the ADC channels. In fact, they even made a point of this in some information at some point. (But it's been a while, maybe 5 years, and my memory is very leaky.) It's not a given that all scanning software does the same, or that all scanners even support it. But I'd expect any high-end device like the Nikons and Minoltas to work the same.

    The light control is useful to adjust for base density of the original. I usually bump it up for transparencies, and set it a little lower for neg (color or B&W). It causes the whole histogram to shift and is needed if the min/max densities are such that the min/max black/white point settings can't contain them. This all gets saved into my film profiles,
    Last edited by Jan Brittenson; 17th December 2008 at 14:50.

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    Re: pushing, exposure compensation ect ect

    Ok, that is a VERY informative answer, but I am still not sure about my question. My problem is that when I have thin black and white negs, the scanner puts out too much light or exposure. Those negs still have detail in them (from the lightbox and analog printing), but their blacks are clipped even if "0" is set as the black point in the histogram. I know that with a positive, I can turn on adaptive light and get more light, but is there any way to get less? To literally turn down the brightness of the scanner light or to decrease its exposure? This would help get a better tonal range with fairly thin black and white negs...
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