Large Format photography group - From "zero to hero!"

StephenM

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Well done for getting your finger out before I'd even moved. The benefits of youth... Where did you find it? I'll admit that having thought about it overnight, I wasn't certain whether the question was optical or chemical i.e. non imaging forming light from the lens or the effect of same on the emulsion.

Of possible interest (from my GoogleDrive).
 
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Woodsy

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The issue is really how one thinks about "contrast". There's microcontrast which is intrinsically linked to both sharpness and chromatic aberration, colour contrast, and what people talk about as global contrast. The latter of which is, I tend to think, the most commonly conjured in ones when someone says contrast, despite it being a little simplistic.

The first of these is clearly affected by lens coatings, but is mostly the result of the optical design and how well the lens performs achromatically over the spectral (visible) range.

The second is not what I'd first think of when someone talks about contrast generally. This is to do with the spectral transmission function of the coatings, and the comparison between uncoated, single coated and multicoated. On a global (over the whole image) scale, this will affect the perceived 'contrast', as certain tones may suffer more of less loss (difference in the transmission percentage) than others, thereby affecting the contrast as compared with a different coating or no coating at all, and indeed the perceived relative brightness between that tone/colour and another. So this is really more the global contrast that people think of outside of contrast that you might alter with general levels in post. The issue is that there are multiple effects which are all amalgamated into the word contrast, some effects are independent, others are linked to one another, so it's really not a trivial thing to explain in a forum post.

Doing what I do, I tend to work from a more fundamental effect upwards. As such, when someone says contrast, I immediately simplify to monochromatic light and go from there. Say for example that you illuminate a piece of perfectly white paper with only a monochromatic light but such that there is a range of illuminating intensities with step-like boundaries (like a test exposure on a new dark room enlarger) - the brightness would be different on one part of the paper than another. If you photograph this, you could say there is range of contrast between the brightness regions. As the light is monochromatic, the lens coating, or lack thereof, will not alter the perceived contrast between the brightness regions when compared to the opposite lens coating case. In other words, if the lens offers 4% loss at that colour or 0.4% loss, and if the overall exposure is the same, the contrast will not change. This is physically impossible without a non-linear process. But, the sharpness at the boundaries between the brightness regions may still change.

Now, as soon as multiple colours are used, as in a real scene, now the global contrast may vary depending on the coatings. But it must be understood that this is a property of the spectral profile of the coatings and hence how different colours are transmitted more or less than compared with another coating or no coating at all. AND, (and this is where my issue mainly comes from) this does not imply that contrast will be stronger. It may well be that, given two colours in a scene, their relative brightness difference may be reduced if the coatings work that way. Therefore the notion of adding coatings always improves contrast is nonsense A) because of the above, and B) because "improve" is a relative term.
 

StephenM

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My simplistic take on the contrast issue runs like this.

1. Non image forming light that strikes the film isn't focused and will increase the illumination over the entire field.

2. This will be uniform.

3. Along the straight line portion of the characteristic curve, density is proportional to amount of light.

4. The increased light from internal reflections will proportionally affect the darker areas more than the lighter ones.

5. The net effect is lighter dark tones with less effect on the high values.

Hence lower contrast.
 

ChrisR

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Presumably "veiling flare" also reduces overall contrast? I would guess that lens design and issues like shiny interior surfaces of the barrel would have a big effect, I'm not sure how much coatings would affect it.

However, maybe if there's more reflection from an uncoated lens, there would be cases where some of that reflected light might end up back in the image. But at 4% (1/25), it's already 4 and half stops down on the main light so I don't see that having much effect... unless there's the sun in the image, perhaps.
 

StephenM

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You might care to read the information I gave a link to in post 1921 above. I found it very interesting to read, and I think you might too.
 

StephenM

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Just as a related aside, some years ago I tested the effect of flare on spot meter readings. I used a black plastic seed tray placed against a white UPVC window frame and took a reading from a distance where the spot fell completely in the black area, but the outer region took in the frame. A second reading from close in, where the black completely filled the viewfinder resulted in a very different reading. I can look up the number of stops (yes, stops, not a half stop) if you're interested. It rather made me think that if you can approach closely enough to fill the frame as it were with a normal reflected meter, it would be just as good (if not better) than using a spot meter from a distance.
 
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Woodsy

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Apologies if this breaks the rules, please delete if so.

If you want a recessed copal 0 lens board, and have a copal 0 non-recessed board going spare and want to swap (No cash either way), please see the classifieds! I need to get sorted by Thursday if possible :)
 

Andysnap

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First evening in Cornwall and already 4 shots taken......all of St Michaels Mount..... Some lovely light and great clouds.
 

Andysnap

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StephenM

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It's far more likely that I've stuffed all four of them
Consistency is a valuable attribute for a large format photographer. I'm sure that they'll all be fine - anyone who can cope with an Ensign folder and red window winding will have no trouble with a simple large format camera.
 
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Woodsy

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4 shots?! Pah! I’ve taken 3 rolls of 120! Looking forward to catching up :)
 

Asha

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anyone who can cope with an Ensign folder and red window winding will have no trouble with a simple large format camera.
Yes I can vouch for that having had numerous red windowed folders.
In comparison LF is a piece of cake!
Consistency is a valuable attribute for a large format photographer.
Good job as my end results are consistently crap!:sulk:
 

Andysnap

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You're not the only one... I shall be staying very firmly on the mainland. :)
 

Asha

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This may be of use to someone:

http://www.salzgeber.at/disc/disc.pdf

I came across it by chance so have printed it out.

Yet to actually use it so can't say how accurate it is but I reckon it's possibly one of the easier methods of calculating compensation for bellows extension
 

StephenM

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It seems like an easier, more direct, route based on the old principle of putting an object of known size in the frame, measuring it on the ground glass, and then using the very simple exposure increase based on magnification that has no squares or square roots in sight.

Well found.

Edit to add:

The simple equation is F = (M + 1) f

where
F = effective aperture
M = magnification
f = marked aperture

In the simple case of 1:1 where everyone knows off the top of their heads that you need a 2 stop increase in exposure, this gives F = 2f, or in other words the lens might say f/8 but it's letting in the light as though it were f/16 - 2 stops less.
 
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Asha

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It seems like an easier, more direct, route based on the old principle of putting an object of known size in the frame, measuring it on the ground glass, and then using the very simple exposure increase based on magnification that has no squares or square roots in sight.

Well found.

I can understand anything so long as it's like me……..SIMPLE! :LOL:

( @RaglanSurf , be careful what you say young man!!!:bat::LOL:)
 
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Anyone shot much of the sheet version of gp3?

I took a few frames on fp4 and gp3 on Sunday morning and the fp4 looks nicely exposed but the gp3 looks very thin both shot at 100 iso (largely because I didn't notice they were gp3 at the time)

I've not scanned them yet so I can't demonstrate but I know a thin neg when I see one.
 

Asha

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Anyone shot much of the sheet version of gp3?
Non at all but I'm interested in what it has ( or hasn't ) got to offer although for a cheap sheet film i on't think you can go wrong with fomapan 100 tbh
 
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Non at all but I'm interested in what it has ( or hasn't ) got to offer although for a cheap sheet film i on't think you can go wrong with fomapan 100 tbh
I'm not sure I've scanned any from before my last hiatus and tbh I'm not sure why I picked it over foma tbh.
 

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I'm not sure I've scanned any from before my last hiatus and tbh I'm not sure why I picked it over foma tbh.
The one and only problem that I find with fomapan 100 is like all it's speeds and formats, the emulsion can be a tad fragile but once you become accustomed as to how to handle it then it poses no problem whatsoever.
Reciricol failure can sometimes actually be beneficial depending what you're shooring.

It's other speeds I don't like but that personal preference.

It's not my go to film, that being delta 100 ( also being drawn back to FP4 sheet film having had poor experiences in smaller formats) but without a doubt if I am unsure wether a particular shot is going to really work out and give me the result that I'm after, then I'll shoot it on fomapan assuming i have some with me at the time of course, so that binning the negative if necessary, doesn't hurt the wallet so much!
 
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It's not my go to film, that being delta 100 ( also being drawn back to FP4 sheet film having had poor experiences in smaller formats)
Generally I shoot everything in fp4, never particularly got on with delta but yeah foma/gp3 for the shots I'm not sure of.
 

Asha

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Thank you for those @desf
I’ve skipped through them and wiiwatch in full tomorrow .
I have come across similar videos and thoroughly enjoy them similarly I’ve watched a guy at one of the photography fairs they have in Paris do the collidion process.... for me it’s like all negative development, it’s not chemistry, it’s magic!
 
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Woodsy

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Anyone shot much of the sheet version of gp3?

I took a few frames on fp4 and gp3 on Sunday morning and the fp4 looks nicely exposed but the gp3 looks very thin both shot at 100 iso (largely because I didn't notice they were gp3 at the time)

I've not scanned them yet so I can't demonstrate but I know a thin neg when I see one.
I've not shot any of it myself, but I believe @Andysnap has? From what I recall from his rumblings on various trips, he rather likes it.
 

Andysnap

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Yes, it's ok really. You need to be careful with exposure compared to more expensive film but it looks ok. I'll pop an example up when I get home, but if you look on my Flickr feed there's a couple taken earlier this year in Cornwall, Godrevy Lighthouse and another of the rocky shore.
 
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Yes, it's ok really. You need to be careful with exposure compared to more expensive film but it looks ok. I'll pop an example up when I get home, but if you look on my Flickr feed there's a couple taken earlier this year in Cornwall, Godrevy Lighthouse and another of the rocky shore.
What do you usually rate it at? 100 iso seems a little optimistic. Though perhaps it just doesn't like pyrocat or needs longer in the brew.
 

Andysnap

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I use Ilford lc39 and Dev it for the same time as fomapan 100, shoot it at 100 as well. It has nice tones I think.
 
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Speaking of user error, just went to load the film from the last two dds from the weekend to find there is no blooming film in one. Not developed the other two sheets yet so not sure which masterpiece wasn't recorded.

Edit: typical I messed up one frame and it wasn't on one of the empty dark slides :(
 
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Just got round to loading some rpx 400 that I bought last year. A little disconcerting that it seems to be roll film cut to size rather than on thick sheets, I'm not sure what effect this may have except that I nearly loaded two sheets in each side of the holder.

Wowser, been a while since i loaded these. As said above, two years ago, its nasty thin stuff but developed fine in the steerman tank with one or two nicks in the emulsion. Not sure I'd rush out to buy any more.

Edit: Correction it did not develop very well in the steerman tanks neg looks like its splattered with fixer.
 
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StephenM

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On Thursday of next week, I should be making my first ever visit to a camera club, to give a talk on large format photography. My understanding is that the meeting will effectively have two halves with a tea break in the middle; the first half will be my chat, and the second will be showing some of my LF snaps.

Clearly, one hour (max) for a chat is a bit limited given the scale of large format as a subject. I've made a sketch of what I intend to cover (but NOT a full script) and if anyone would care to comment on bits missing/superfluous I'd be grateful. You can pick up the text and illustrations here:

https://1drv.ms/u/s!AvzjN1vsy206grs_0Ga8uKHdUaXYxA?e=FQZVCd

The photos are all mine, except for the different camera types lifted from the internet. On the text, red text indicates photos to show, green things I intend to do/perform/demonstrate and in the one case of italics I explained what I intended to someone who was already looking at the text. This section on distortion could be easily dropped if time presses - it's near the end.

I was intending to take a number of cameras and lenses along, together with fogged film and holders for people to play with, so this is also to be factored in for the time.
 
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