Chroma - Lasercut Acrylic 4x5 Field Camera

ChrisR said:
You're not alone, although I've been shooting film for years (decades, really), I've never thought for LF before. I've just been reading and researching like mad. The web sites mentioned by Steve above are good pointers (I;ve been meaning to mention them on the LF thread here (zero to hero).

One thing I found is that the 120-ish lenses are quite a bit dearer than (some) 150s, indeed I reckon I might be able to get a Fuji 90 and 150 for about the price of a Fuji 125!

Also, most of the lenses are from Japan, need to factor in 7% import duty, 20% VAT on top of that, plus £8 ransom from Royal Fail.

Also, many listings don't tell you the lens board, or mention a lens board I've never heard of. Many don't mention the shutter (ignoring "enlarging lenses" which AFAICS are a different thing).

One thing @StephenM has mentioned: the enlargement from a 4x5 negative to a 16x20 picture on your wall is the same as the enlargement from 35mm to a 6x4 snapshot... ergo the quality of the lens is much less important unless you're going much bigger still. And most of the lenses are supposedly pretty good.

Slower lenses presumably mean dimmer images on the ground glass for focusing, more need of a dark cloth...
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From my own research, 120mm lenses appear to be less common so are therefore more expensive. Also, they're not quite as extreme as a 75/90mm lens or as 'normal' as a 150mm which I think also gives them some scope for higher prices.

You're right about 'slower' lenses. It's easier focusing on a ground glass with a lens at F5.6 than it is at F8 (for example)
 
stevelmx5 said:
From my own research, 120mm lenses appear to be less common so are therefore more expensive. Also, they're not quite as extreme as a 75/90mm lens or as 'normal' as a 150mm which I think also gives them some scope for higher prices.

You're right about 'slower' lenses. It's easier focusing on a ground glass with a lens at F5.6 than it is at F8 (for example)
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Yes I was definitely aiming for a 125 mm as a good compromise, but I've backed away somewhat now.

One resource I read pointed out that the (inverse?) crop factor depends on how you shoot, because of the different aspect ratios of 135 and 4x5. So he suggested that if you normally shoot landscape, the ratios of the long sides count, so 5"/1.5" = 3.33 crop factor, while if you normally shoot portrait the ratio of the shorter sides count, ie a crop factor of 4. Not sure I quite buy the argument, but even 3.3 renders a 150mm lens more like a 45mm in 135 (a pretty rare lens, if any exist, but a slightly wide normal).
 
ChrisR said:
You're not alone, although I've been shooting film for years (decades, really), I've never thought for LF before. I've just been reading and researching like mad. The web sites mentioned by Steve above are good pointers (I;ve been meaning to mention them on the LF thread here (zero to hero).

One thing I found is that the 120-ish lenses are quite a bit dearer than (some) 150s, indeed I reckon I might be able to get a Fuji 90 and 150 for about the price of a Fuji 125!

Also, most of the lenses are from Japan, need to factor in 7% import duty, 20% VAT on top of that, plus £8 ransom from Royal Fail.

Also, many listings don't tell you the lens board, or mention a lens board I've never heard of. Many don't mention the shutter (ignoring "enlarging lenses" which AFAICS are a different thing).

One thing @StephenM has mentioned: the enlargement from a 4x5 negative to a 16x20 picture on your wall is the same as the enlargement from 35mm to a 6x4 snapshot... ergo the quality of the lens is much less important unless you're going much bigger still. And most of the lenses are supposedly pretty good.

Slower lenses presumably mean dimmer images on the ground glass for focusing, more need of a dark cloth...
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All modernish postwar large format lens were made with Professional use in mind, so started life as "professional" quality.

What might surprise amateurs is the generally modest maximum apertures.
Those designed for technical and monorail cameras usually have a far wider coverage than those with wider apertures designed for press type cameras.

At first glance those designed for use with movements usually look extremely Wasp waisted, with large front and fairly large rear elements.
Earlier designs like the Angulon are surprisingly small, but were designed to be used with the aperture well closed down, the open aperture is only suitable for focussing.

Prewar large format lenses often came with no shutter at all. As the shutters were separate beasts. Often Focalplane , or some sort or roller blind mechanism used either in front of or behind the lens..
It is amazing how good these early lenses are, though uncoated and relatively simple designs. they would have no trouble at all, producing excellent 20x16 prints. after all for a 5x4 negative that is only a 4x enlargement... and from a 10x8 film only 2X. However unlike their modern counterparts some were economy versions, aimed at Amateur use.
 
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135 is more common than 125, I've got the little 125 fuji, its a great landscape lens as its very small (for a wide angle lf lens) but it doesn't have a lot of coverage to spare. I've got an older schnider 135 which I've not tested yet but once I'm satisfied it works correctly and I'm not going to use it I'll stick it on the clasifieds.
 
If I remember correctly, some fixed lens 35mm cameras in the 1960s had a 45mm lens.

In my experience, the conversion factor for focal lengths falls down because I favour different lens sets depending on format size. On 35mm my 2 lens outfit was 21mm and 90mm macro on my OM1; whereas I've never felt the need to drop below the 110mm lens on my RZ67 (except once, when I simply couldn't step back any further). My preferred 5x4 lens is 210mm, which again is slightly long. On the other hand, after getting my first SLR with 50mm lens, the second lens I went for was 135mm, so I've always preferred the longer focal lengths. So, in brief , it may depend on personal preference tempered by the proportions of the format more than any mathematical relationship.
 
From the 1960's professionals had settled down to a surprisingly few Large format lenses for use on 5x4

My own choice in those days was for a F5.6 90mm Super Angulon. A convertable Schneider Symmar 150 mm 5.6 lens, (converted to 265mm) by removing the front elements.
I later added a Super Angulon 75mm which came out mid Sixties and I replaced my Symmar with a 150mm and 240 and added a 500mm Tessar which covered 5x7.

My copy of the Symmar 150mm produced stunning results in its basic form. and excellent results converted. but you also lost a lot of light by extension.
However today, and at likely enlargements, the quality of all these lenses would be way beyond most needs.
Unlike us you, are unlikely to need to be able to do 3 meter square prints.
 
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StephenM said:
If I remember correctly, some fixed lens 35mm cameras in the 1960s had a 45mm lens.
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Yes - my first camera (in the 70s) was a Canonette Junior with a fixed 40mm f2.8 lens. Same focal length as the very popular Olympus Trip.

It's reassuring to know that pretty much all the lenses for large format are of good quality, and certainly more than up to the task of producing high quality images.

I'd just like to say thank you very much everyone for quickly coming back with so much information and links for further reading. I've already learnt a lot more than I knew a couple of hours ago, and am getting more and more certain that I'd like to give 5x4 a try with the Chroma. Also it'll give me something to look forward to for later on in the year.

Cheers,

Conrad.
 
StephenM said:
If I remember correctly, some fixed lens 35mm cameras in the 1960s had a 45mm lens.
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The general reckoning is that the correct 'normal' lens for a camera is equal to the diagonal length of the frame. For 35mm, this is around 43mm and for 5x4 it's around 162mm.


Steve.
 
C&C said:
Ok Steve,

That's one more (probably matt black) Chroma you're going to have to put together.
Just subscribed.

Looking forward to an interesting November!
....goes off searching for lenses and film holders...... :)
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That’s brilliant, thanks a lot for that [emoji1303] I’ve actually got a matt black Chroma here that I’m assembling now;

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This is the updated shape with engraved marker lines so you know that the front standard is straight.
 
I've been dithering about colours too, not that I remember the choices available. Black would be boring, OTOH purple or dark red might be a problem if it turns out LF is not for me and I want to sell it!
 
The thought did cross my mind, so I'll ask: given the modular construction, will you be selling "mix'nmatch" versions with one colour bed, another for the front standard and a third for the rear? With a fourth colour for the lens panel? :D

As a selling point - I have my LF lenses in an aluminium case, and given that the sizes aren't very different, I have to lift them out to see which is which. Imagine the convenience for recognition of having different focal lengths on different colour boards...

Edit to add: I still like the idea of tartan bellows. If the French can do it...
 
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StephenM said:
The thought did cross my mind, so I'll ask: given the modular construction, will you be selling "mix'nmatch" versions with one colour bed, another for the front standard and a third for the rear? With a fourth colour for the lens panel? :D

As a selling point - I have my LF lenses in an aluminium case, and given that the sizes aren't very different, I have to lift them out to see which is which. Imagine the convenience for recognition of having different focal lengths on different colour boards...

Edit to add: I still like the idea of tartan bellows. If the French can do it...
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Funnily enough....

The Chroma #0 is the £1000 charity camera that's I've said can be made to any colour specification/engraving the backer wants. I've already been chatting to them about having a blue bed and yellow front/rear standards to match their charity colour scheme so it may happen. Potentially, I could use a different coloured piece for every individual layer of the camera too so it may appear down the line :0)

That's a good idea about the lens board colour coding too. I've already engraved some of my lens boards with the shutter size so I knew which was which but a completely different colour could be used.
 
ChrisR said:
Dark red? British Racing Green? (Now that would be classy!)
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Mrs Nod's XK8 is BRG - the Jag version. Aston Martin, Bentley et al. had different greens but all are classed as BRG (green was the colour allocated to Britain when nationalities were assigned colours under which to race, hence red for Italy, blue for France, white for Germany (until they realised that they could leave the cars in polished Al and save the weight of the paint - silver arrows.)

And yes, it's a classy green!!!
 
I think those two greens in the second row must be pretty close to BRG. Not sure how it would look with the black bellows though, might be a little too understated!
 
Stealth!
 
Thanks to some great help from @SteveSmith I’ve now got a working spring back using FR4 (fibreglass reinforced plastic) spring plates [emoji1303]

View: https://instagram.com/p/BgCDcgtgyp4/


The final design has these secured using a pair of thumb screws from the top most rivnuts on the frame along with a pair of Graflok style locking clips either side to secure rollfilm backs or any other backs that are too think to go under the ground glass. The idea is that if you’re shooting with a rollfilm back, you would disconnect the spring plates from the camera back and secure the ground glass using the Graflok plates. Once you’ve composed, the ground glass can be removed entirely (with the spring plates still secured to it) and the rollfilm holder dropped in and secured with the Graflok plates. For standard DDS holders, Quickload or my wet plate holders, the groundglass can stay in place.

I’ve also fitted a pair of small round bullseye levels alongside the larger level in the bed of the camera. The new levels are mounted in the rear standard and front lens board frame so you can ensure complete levels.

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The two loops are mount points for a nylon strap that will be fitted for easy carrying.

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steveo_mcg said:
So have you dropped the magnets on the back?
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I've dropped them for securing the ground glass in place but still use them to secure the entire rotating back to the rear standard. I was happy with the magnetic mount for the ground glass but had images of people accidentally knocking it off down the side of a cliff! The spring back/Graflok plates are also much more universal so any back that works with those will work on the Chroma out of the box.
 
stevelmx5 said:
The idea is that if you’re shooting with a rollfilm back, you would disconnect the spring plates from the camera back and secure the ground glass using the Graflok plates. Once you’ve composed, the ground glass can be removed entirely (with the spring plates still secured to it) and the rollfilm holder dropped in and secured with the Graflok plates. For standard DDS holders, Quickload or my wet plate holders, the groundglass can stay in place.
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I've ben having trouble imagining this. At first I thought with a rollfilm back I'd be undoing those two bolts every frame, but if I (now) understand this correctly, that only happens at the start (and end) of a rollfilm session? But still remove the ground glass from the Graflock holders and clip the rollfilm back in place for each shot?
 
stevelmx5 said:
Thanks guys. It's nice to be able to do my part and help what appears to be a very worthwhile charity. We're talking over design ideas now and the backer has also asked about the possibility of mounting his Sony A7iii to the Chroma for some digital panoramic shots. He's not the first to ask so I've drawn up a slider back which will fit direct to the rear standard in place of the Graflok back;

View attachment 120856

View attachment 120857

The back will give 25mm of movement each way when the A7 is mounted which should allow for 3 image panoramics to be taken. I need to build one to find out the best alignment but it looks ok on paper. The whole back can then be rotated (using the same embedded magnets that the Graflok back uses) to shoot horizontal panoramic images. The other back is the 612 holder and the unit to the right is the complete Graflok back with groundglass in place.
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Also having trouble imagining how this will work... in particular, what is the A7 focusing on? In normal use, the light from objects "at infinity" arrives as parallel rays, but the Chroma is going to focus those to converge at the film plane. So is the A7 essentially using a very short focus onto the film plane to see those distant objects?
 
ChrisR said:
I've ben having trouble imagining this. At first I thought with a rollfilm back I'd be undoing those two bolts every frame, but if I (now) understand this correctly, that only happens at the start (and end) of a rollfilm session? But still remove the ground glass from the Graflock holders and clip the rollfilm back in place for each shot?
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Yes, that’s pretty much it. The rolllfilm back is too large to fit under the spring back (as with all large format cameras) so it used the Graflok plates on each side to clamp the into place. The groundglass can be secured using the same Graflok plates so it can be fitted, the image focused/composed, removed entirely by sliding the Graflok plates and the rollfilm back slotted in to expose the image.

If you look at the Intrepid, they do the same thing for larger backs except they use the heavy bungee cords to secure the ground glass plate whereas I use the spring plates.
 
ChrisR said:
Also having trouble imagining how this will work... in particular, what is the A7 focusing on? In normal use, the light from objects "at infinity" arrives as parallel rays, but the Chroma is going to focus those to converge at the film plane. So is the A7 essentially using a very short focus onto the film plane to see those distant objects?
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All the lens does is converge light onto the film plane. I’m removing the the entire film back and mounting a new plate with the A7 and its’ sensor replaces the film plane. There’s no lens on the A7, it’s mounted directly to a tube/mount on the slider plate and the lens is adjusted until the image is focused on the digital sensor. There’s no need for a ground glass to focus as you can just use the digital image on the rear screen of the camera.
 
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stevelmx5 said:
There’s no lens on the A7, it’s mounted directly to a tube/mount on the slider plate and the lens is adjusted until the image is focused on the digital sensor. There’s no need for a ground glass to focus as you can just use the digital image on the rear screen of the camera.
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Aha, the lack of A7 lens is the bit I missed. Might be a bit of a dust bunny problem leaving the lens off the A7 for a while? Not that this would trouble me, of course, I get a fresh sensor every time! :)
 
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