stefan1

Hello Cedric - I'm the same situation as you were when you posted. Did you solve the software issue?

Thank you both for the replies. I can't seem to find LPD over at Kodak(.com) - I might have to find a solution involving sheet film instead.

I am having a hard time finding 35 mm lith film. Kodalith is

discontinued and I can't seem to find any alternatives. The

application I need it for is pinhole and zone-plate apertures. Any

suggestions for alternatives (film or technique to get deep black/very

transparent and not grays inbetween).

What is the reputation/quality of DKE brand filters? Having a hard

time digging up info on these... Any feedback would be appreciated!

Thank you Oliver - elsewhere somebody referred to "NB" as standing for "New Barrel", but I have also seen that it is a different name for the "C" class lens. A little confusing, but it is good to know that I probably can't go too wrong with an earlier lens which will probably fit on the body I get since that too will certainly not be a brand new camera...

I am trying to sort out the differences between the various Mamiya RB67

lenses series. I have the categories down as:

 

pre-C

NB

C

KL

 

KL is the current line of lenses and they are generally highly

recommended in what I've seen. Do the classes differ mainly in how they

are coated, or are there other significant differences that make a

difference? "NB" lenses appear rather affordable and would fit my

budget, but what are their drawbacks compared to the later models?

 

Some knowledgeable input on these lenses would be greatly appreciated.

 

Thanks,

 

Stefan Engström

Looking at that code I am not entirely sure what it actually does with the information in the file, but basically yes - plus latitude for the many choices that are possible for the conversion to b/w.

 

It may be a non-issue, but it seems that it would be advantageous to make the conversion as close to the sensor data as possible.

Nevermind the 8-bit storage as it is an uncessary limitation if one were to convert raw to b/w. What I wonder is if the conversion to gamma-corrected (or even linear) RGB mapping is losing enough information that it would be worth considering to do the conversion in one step instead of two.

 

While I'm all for using color information to have latitude in the b/w conversion, but for me the Russel Brown layer method is not always the best way to convert to b/w.

I have recently read a little about the details in translating the

usual Bayer pattern raw capture to a color image, especially one that

fits in 8 bits per channel. I also have an interest in finding

satisfying ways to create b/w from color images...

 

It seems that the b/w conversion might get an edge if it used the raw

data directly since it could then use the unadulterated linear capture

and apply whatever color-to-b/w map it wants to use directly instead

of going through the degrading step of converting to gamma-adjusted

color first.

 

Any thoughts on this. Has it been done already?

The histogram is a global measure and contrast is a local property so the only strong relation between the histogram to the contrast is that it is a prerequisite for a high-contrast image to have both light and dark values represented. An image with peaks at the high/low end tends to have high contrast. Midtone expansion (pushing values towards this bimodal distribution) is a way to enhance contrast, midtone compression (the opposite) tends to reduce contrast.

As noted above you need to think about what distance will this be viewed? I've seen great 16x20 prints made from <=4 Mpix cameras. Be it that they were nice cameras (Nikon D1H, Canon 1D), but the prints were hanging behind the counter an at the distance I was viewing them, they look quite wonderfully sharp.

I don't think I have the experience or eye for detail that you probably do, but for some reason it seems to me that this is a transition problem and not something inherent in shooting digital vs. slide.

 

If you want exact color you do need a calibrated workflow using profiles for your monitor and the printer you are using (whether it be your own or a pro shop). The local pro shops here will give you their color profiles and expect you to adapt to it - not very consumer-centric, but supposedly it works.

 

If you are happy with what you see on your monitor, then you should be halfway there if you have a color-calibrated system...

 

Straight contrast adjustment in PS is not what I use to fix contrast if I need to - histogram or curves adjustments gives more flexibility.

 

Could you show a photo (from digital) that has the contrast problem you are talking about?

It would be interesting to see an image of what you think is the problem.

Just to check the obvious: you did remove the white cover used for reflective scans to allow the transparency backlight to operate? :-)

 

I've had mixed success with using "full auto mode" for anything but reflective scans (where it works really well), sometimes with the result of scanning the underside of the transparency adapter when I'm doing film.

 

What I do as the "Scan and Save" application kicks in is to change "full auto mode" to "professional mode" where you get the most control over what is going to happen.

Apart from estethics regarding the process itself, what are the advantages of a high-output source other than a faster exposure time? Is the contrast better? Does it matter if the incident light is very diffused (my lighttable) or should it have parallel incoming rays?

 

I was assuming that brighter is better and parallel would be better than diffused, but some people seem to think that open shade is better than direct sun, and that goes against both of those assumptions.

The article (should I say treatise :-) on unblinkingeye was extremely helpful - thanks Sandy for writing it and providing the link.

 

Any thoughts on using a light-table for exposures? Is the diffusion bad for contrast? It is really convenient, but two 40W BLB lights will cost about $40 so maybe I'll try that eventually. I do like the idea of being able to generate consistent exposusures...

 

Is the duration of exposure also a factor in what contrast can be achieved? Is there a difference if the light source is weaker but the exposure time is longer?

 

Anyway - thanks again for the all the helpful suggestions.<div></div>

Thanks for the suggestions. I did try sunlight which gave me a nice full exposure with about 10 minutes of midday January sun in Nashville, TN. I also tried to put the contact frame on top of my ligth table with two flourescent tubes in it and that gave me a decent exposure in about 20 minutes, but in retrospect I think a littel longer would not have been a bad idea.

 

From some other reading on the web it seems that UV-A is what you want and UV-B and UV-C (shorter wavelengths) does not necessarily help.

 

I was pretty happy with the exposure from the light table, but I'm concerned that the light being diffused so close to the contact frame is not the best thing for contrast - I'm imagining that ligth strictly normal to the contract frame would be the best way to fly.

 

I am looking for a face solarium on the ebay as well, but nothing or yet :-)

 

Thanks again for the feedback. -S

I need a way to expose 8x10 cyanotypes. A halogen lamp with the UV

screen removed works but it takes about one hour for the exposure.

What is the wavelengths the process needs (I'm using the "new

cyanotype" method)? Would a "black light" flourescent tube work?

Their output seem to be rated around 365 nm. Is that good enough?

 

Any comments or suggestions for other routes would be appreciated!<div></div>

I did upgrade to version 4.5 but it did not solve this problem. Thanks for the suggestion though.

I use the custom white balance quite a bit with my G3 (shot of a

gray card in strange ligthing) and it works really well, but for

some reason shooting to raw format really screws up the conversion

to tiff or jpeg. I can't seem to extract . I only have the Canon-

supplied software for the conversion (ZoomBrowser). Is this a know

bug; is it just me; can something be done about it? In the setting

for white balance in ZoomBrowser the custom setting is not even an

option, and using the "shot settings" gives me a sickening green

cast to the image (see attached file), whereas the thumbnail version

in the raw file looks ok.<div></div>

I think Steve Chan has it right about the current status of sensors. The low (dark) bits are going to be noisy in just about any camera... Yet another possible advantage of having (say) a logarithmic response in the sensor is that one could spread the available bit depth down to those difficult-to-resolve dark areas. As it is now in a linear sensor, you spend half of the bits on the first stop of exposure, half of the remainder on the next stop, and so on. This is assuming that you push the exposure all the way up against the right hand side of the exposure histogram, it just gets worse if you don't. Even if you can reach deep bit-wise, it is important to remember that zones are not given equal weight in the capture.

Just to clarify - with post-processing I include in-camera processing. What I'm wondering about is a non-linear cmos/ccd element.

 

One application would be to avoid highlight clipping, but another issue I had in mind is scenes where the contrast is very low and I'd like to spend my 12-16 bits on (say) only two stops of exposure.

 

@Neil: Programmable gain in scanners after the CCD does not really make sense to me. Isn't it the sensor itself that has to be modified if you want more film-like response (sigmoid logarithmic instead of linear), plus the light situation in a scanner is about as well defined as you can hope for. Agreed, if you have very heavy negatives you might benefit from having some extra amplification but that seems more like a rescue mission feature rather than something you need on a day-to-day basis.

Is there such a beast as a digital camera with variable contrast? If

not I wonder how hard it would be to make...

 

Another related topic is that of non-linear sensors which could

provide a way to avoid clipping highlights. Again it is a hardware

issue and possibly of too little interest to be commercially viable,

but wouldn't it be nice to have something that responds a little

more like film with over-exposure?

 

I do understand that it is possible to do these things in post

processing but with loss of quality unless the capture is very deep

and not at all noisy.

Color filters are theoretically but not practially made redundant (as Nestor argued) by digital capture. Say you want to simulate a red filter which lets in 2 stops more red than anything else. In theory you can just decrease blue and green in your RGB mix, but the overall exposure may not be what you want, and you may then not have the latitude to tweak that in PS.

Fair enough. I'm just trying to avoid burning through too much film and time just getting an exposure somewhere near the proverbial ballpark.