Saturday, 28 February 2009

Lightroom tip: selective masking

Ears up, Tanzania, January 2009

Lightroom 2.2, Windows XP
Read my tips intro if you're new.

Why is the brush tool so slow?

I've been doing quite a bit of brush work with Lightroom recently, especially playing with selective desaturation. I was getting frustrated by system slowdown and hang-ups so I went off to find out what's going on. what follows are some of the details, skip down to the Advice section for the what-to-do part.

In general, for small curves, limited regions and editing only a few images with the brush in a session, Lightroom 2.2 is very responsive. If, however, I start running large areas, many images in sessions or lots of changes, problems jump up.

How does Lightroom create the mask?

This is the central part of the problem, I think. When a mask is created, each stroke of the brush is saved as a separate multi-point curve. you can check this by saving the metadata to and .xmp file and opening it. the Mask has the form:

[crs:PaintBasedCorrections]
[rdf:Seq]
[rdf:li rdf:parseType="Resource"]
[crs:What]Correction][/crs:What]
[crs:CorrectionAmount]1.000000[/crs:CorrectionAmount]
[crs:CorrectionActive]true[/crs:CorrectionActive]
[crs:LocalExposure]0.000000[/crs:LocalExposure]
[crs:LocalSaturation]0.600000[/crs:LocalSaturation]
[crs:LocalContrast]0.000000[/crs:LocalContrast]
[crs:LocalClarity]0.200000[/crs:LocalClarity]
[crs:LocalSharpness]0.000000[/crs:LocalSharpness]
[crs:LocalBrightness]0.000000[/crs:LocalBrightness]
[crs:LocalToningHue]356.000000[/crs:LocalToningHue]
[crs:LocalToningSaturation]0.000000[/crs:LocalToningSaturation]
[crs:CorrectionMasks]
[rdf:Seq]
[rdf:li rdf:parseType="Resource"]
[crs:WhatMask/Paint][/crs:What]
[crs:MaskValue]0.900000][/crs:MaskValue]
[crs:Radius]0.023269[/crs:Radius]
[crs:Flow]1.000000[/crs:Flow]
[crs:CenterWeight]0.000000[/crs:CenterWeight]
[crs:Dabs]
[rdf:Seq]
[rdf:li]d 0.321572 0.469314[/rdf:li]
[rdf:li]d 0.326572 0.462008[/rdf:li]
[/rdf:Seq]
[/crs:Dabs]
[/rdf:li]
[rdf:li rdf:parseType="Resource"]
[crs:WhatMask/Paint][/crs:What]
[crs:MaskValue]0.900000[/crs:MaskValue]
[crs:Radius]0.023269[/crs:Radius]
[crs:Flow]1.000000[/crs:Flow]
[crs:CenterWeigh]t0.000000[/crs:CenterWeight]
[crs:Dabs]
[rdf:Seq]
[rdf:li]M 0.891740 0.296029[/rdf:li]
[rdf:li]M 0.894016 0.305266[/rdf:li]
[/rdf:Seq]
[/crs:Dabs]
[/rdf:li]
[/rdf:Seq]

[/crs:CorrectionMasks]
[/rdf:li]
[/rdf:Seq]
[/crs:PaintBasedCorrections]

the bit in bold shows two sets of points for two strokes but for a single region. Here I've replaced all the xmp <> with [] so it doesn't get screwed up by Blogger.

If you create a large mask (as I did for the whole leopard in the shot above) then you can end up with many lines, each with thousands of points. If you really want to get anal, these can be edited down with a text editor. Easily half the points can be removed (alternate points). tedious, and not recommended.

The more you edit, the more points are generated. If you have to go back over sections, you end up with lots of overlapping lines, and repeated work being done. I think, by experiment, that Lightroom is set up to interpret each line independently, which then goes to defining the area for applying the adjustments for a give brush mask. If you've got thousands of points, that's going to take time. So I suggest using some care, and good painting technique to improve things.

Advice

So here is my advice, particularly for large areas, in this order:

1. Use the mask overlay to show the mask as you paint (key O)
2. Start with a large brush and smooth continuous strokes for large areas.
3. Use the lowest flow you can get away with (cuts the number of points generated). Faster brush work needs a higher flow.
3. Avoid reworking areas
4. Zoom in and use a smaller brush for details and edges (generally with a lower flow, and slower brush strokes).

That should help cut down the number of points generated, and the number of line segments, which should maximise performance.

Thursday, 26 February 2009

Wednesday, 25 February 2009

First review at Photo Exhibit

Doug Stockdale is editor-in-chief of a newish blog Photo Exhibit for reviews of photography exhibitions, gallery shows etc.

I've agreed to contribute and have just posted my first review on the Man Ray exhibition at The Hague's Fotomuseum.

I think this is a pretty good endeavour, go check it out.

Nothing to fear except fear itself

My, what big teeth you have, Tanzania, January 2009

Paul Butzi and Gordon McGregor have been writing about completion inertia. Anita Jesse had a good post about general project inertia. I thought I'd chip in my bit.

I'm like Gordon and Paul - like to get going, prove stuff can be done, extract the goodness and move on. I'm not a completer by any means. Starting, however, is never a problem.

Here's my thinking: if it's not going to kill me or land me in jail, pretty much anything is worth a try. Certainly a photographic project has few negative consequences if it fails. If I have confidence in my abilities to do something, then I have confidence to get on with it. That confidence comes from proving to myself I have all the individual skill elements, I just need to bolt them together. So far, so good.

I've learnt that to complete stuff, I need to make the end run easy on myself. Line everything up ready for a quick blast for the finish line. In photography terms that means severl things. Knowing I have enough material for the project, being decisive in selecting and editing - first impressions, good is good enough - and a fairly mechanistic means of completing a layout (for a simple layout, I can go from list of selected photos to compeleted book in a couple of hours). Planning is key - lining things up for an easy effort. that bit i'm pretty good at.

thus my key strategies for getting projects done: having confidence in my ability to do the thing and clearing the path for an easy finish. This is a similar strategy I apply in my day job and it gets me past the main slow points.

To close, another from FDR:
Take a method and try it. If it fails, admit it frankly, and try another. But by all means, try something.

Tuesday, 24 February 2009

Unconcerned but not indifferent: Man Ray

Entrance poster

This has been a well-publicised exhibit, a large retrospective covering the whole of Man Ray's life and work at the Hague Fotomuseum. An ambitious undertaking but can it be completed successfully? Let me begin by quoting from the press material
Unconcerned, but not indifferent is the first exhibition to reveal Man Ray’s complete creative process: from observations, ideas and sketches right through to the final works of art. By establishing the linkage between art and inspiration, it gives a new insight into the work of Man Ray.
Lofty ambitions for any exhibition. This idea of creative connections, and how the artist is influenced by his relationships is always of interest to me - bringing that to an exhibition is what moves a museum past being a mere gallery. The work on display is divided chronologically across the 4 periods in Man Ray's life; his early life in New York, moving to Paris before the war, escape to LA and a final return to Paris in 1951 until his death in 1976. In effect, though, the first period has little coverage and serves as a mere foreword to the rest of the work. There is a wide range of material on display - much photography, obviously. But also drawing, painting, sculpture and some of the famous "Rayographs" and materials used. The photographs are not great prints, although originals. Man Ray doesn't seem to have been what would be considered a "master print maker" but that is in keeping with his general philosophy (from the exhibit):
The mass production of his work always appealed to Man Ray, who had always had a tenuous relationship to the aur of art objects. the act of making a unique object, he claimed, was validated by its reporduction, by means of which the inspiration, or idea, was disseminated.
The photographic prints are actually quite small, although framed in such a way to draw the viewer in. Often several are framed as a group together, which adds context. So far, so good.

A wide range of exhibits: sketches, paintings, sculpture and, of course, photographs

The drawback of this range and variety of coverage is that it is necessarily fairly shallow. No particular area gets into any depth. The explanatory texts are brief and few, so I got very little sense of the connections between the man, his relationships and his work. I was left with many more questions than answers: When did his first marriage end? How did that relate to his relationship with Kiki de Montmartre? There was evidence of changes in stles and work - was that driven by changes in relationship or conscious development as an artist? What exactly was his relationship to contemporaries in Paris? As presented, Man Ray seemed little more than a portraitist to the stars, which is far short of the truth. How did Man Ray's work progress through ideas, photographs, painting & sculpture - which lead and which followed? Did this change over time (as seemed to be the case)? I would have liked to see rather more in the way of explanatory panels and text throughout. So what is my overall assessment? I think a less ambitious scope would have allowed greater depth of coverage and more exploration of the ideas. In many ways the exhibition falls short of the lofty ambitions. However, it is definitely a worthwhile exhibition and worthy of the modest entry fee but a little effort would have made it so much better. Visitors would be greatly rewarded by a little Man Ray research in advance.

Sunday, 22 February 2009

Sagacious Pachyderms

Angry lady, Tanzania, January 2009

Apart from the fact that pachyderm is a defunct term...

Animals had varied reactions to our presence in Tanzania. For the most part, we were completely ignored, as if the vehicles were just part of the landscape (noone gets out near the wildlife). When moving, most herd animals would avoid us. Cats seemed unmoved. Those below were using the shadows as shade.

Close encounter, Tanzania, January 2009

Elephants, on the other hand, seemed fully aware of the presence of the vehicles and their occupants. This one above one part of a group protecting a new-born. At this particular point in the proceedings it seemed possible that she would charge the vehicle. she did stomp alongside us, clearly unimpressed.

A few minutes later, rounding a corner there was anoher elephant looking to cross the road. We stopped. She tossed her head in a "out of my way" motion - no intention of deviating. We moved. Elephants are clearly unintimidated by the presence of a couple of tons of metal.

The Genius of Photography (2)

I managed to miss the first series, but I've just finished watching the first episode of the BBC's new series of "The Genius of Photography". An excellent series looks to be starting.

This episode ran from the birth of photography, Fox Talbot & Daguerre, through Eastman's early Kodak cameras through to Lartigue and the birth of Pictorialism.

A lot of images, a lot of erudite commentators but presented clearly and informatively. I particularly like the way the photos are presented - some zoom & pan to see the details, then a full view with caption and photographer. Sort of like visiting a museum but in moving pictures.

Well worth looking out.

Wednesday, 18 February 2009

Pretty beautiful

Natural born killer, Tanzania, January 2009
All baby animals are cute, until you see one rip the leg off a dead wildebeest calf
Pretty: pleasing or attractive to the eye
Dictionary.com Unabridged (v 1.1). Random House, Inc. http://dictionary.reference.com/browse/pretty

Beautiful: having qualities that give great pleasure or satisfaction to see, hear, think about, etc.
Dictionary.com Unabridged (v 1.1). Random House, Inc. http://dictionary.reference.com/browse/beautiful
From The Landscapist:
For me, the difference between "beauty" and "pretty" is all about depth. "Pretty" is all about surface. "Beauty" is about what lies beneath the surface. "Pretty" stays on the surface of things. "Beauty" dives/delves into the deep. "Pretty" is simple. "Beauty" is complex. "Pretty" embraces the straight and narrow. "Beauty" embraces contradictions. "Pretty" is contrived and self-absorbed. "Beauty" is comes naturally and is outgoing.
Go read the whole post, there's nothing I'd disagree with in there.

Nature is beautiful because it is rugged, adaptable, unsentimental. That's the truth I hope I can get at in my photographs.

Tuesday, 17 February 2009

SoFoBoMoGo 2009

If you've not seen already, SoFoBoMo 2009 is go.

If you're new to the concept here's the synopsis:

SoFoBoMo, the Solo Photo Book Month, is a challenge to anyone with a camera to spend 30 days taking pictures and putting at least 35 of them together as a book. It's fun, it's challenging, it gets you thinking about photography in ways you've never done before, it connects you with other like minds.

Take part, there's nothing to lose and much to gain.

Monday, 16 February 2009

A note on Canon Auto-ISO

I discovered a useful implementation of Auto-ISO on canon cameras (at least on the 40D & 50D), which doesn't appear to be in the manual. Some of you might find it useful/interesting.

In Av mode, the Auto-ISO feature prioritises ISO over shutter speed. That is, the camera aims to set the shutter speed before changing ISO until it hits a lower limit shutter speed. Simple stuff. However, it has a smart implementation of minimum shutter speed. The camera reads the focal length from the lens and then uses the 1/f rule for setting the minimum.

Here's an example: Mount a 70-200, zoom at 200mm. Set Auto-ISO. Set aperture. Shutter is adjusted until it hits 1/250s, then ISO is adjusted up until the maximum, then shutter is further reduced to match metering.

Mount a 500mm lens, minimum shutter target is 1/500s. Add the 1.4x tele-converter (700mm) and it goes to 1/750s.

Image Stabilisation doesn't affect the minimum shutter speed, which is nice.

The draw-back with the 40D is the Auto-ISO range is limited to 400-800. (I'm sure they could fix that with firmware.) On the 50D that's been fixed to be 100-1600. If I was a 50D owner, I'd use auto-ISO all the time.

More on camera controls

After my safari thoughts, I was reminded of the post I made on camera controls. Given that I used my camera in entirely new ways in Tanzania, I've had more thoughts on camera control.

If I can't have the simplified camera I want, how about having a camera that I can set up to my liking? I've become increasingly frustrated with some of the button-function choices of Canon (but other companies don't seem any different) and the way they cripple the lower models. Seeing what gets done with the pro camera custom functions it should be easy to give us more control over the control.

Here's a few things I'd like:

  • Dedicated operations. Aperture on one dial, shutter speed on another, I choose which and I choose independently the direction of operation. A dedicated ISO dial.
  • Auto-ISO range that I can set. Auto-ISO in manual mode. I should be able, in manual, to set shutter, aperture, compensation and the camera determine the ISO.
  • MLU button. There must be three or 4 buttons I never use which could easily do the duty (e.g. the direct print button).
I would have ranted about a separate focus button but most cameras now have a thumb operated focus button (or option to set up one). This is now my default - focus and shutter release are independent.

I know all of this is doable, because Canon almost has the lot in the 1DmkIII cameras - nearly but not quite. Why they can't have a set of custom functions, one per button, for personal set-up beats me.

Sunday, 15 February 2009

Finally, my first blurb book


After the trials and tribulations of print settings etc, I've received full copies of my book "Kristiansund". I must say, the quality of the final product is very nice and the quality and tone of the images is spot on. The hard cover is especially good: quality binding, fly leaves etc.
It's now at Blurb.

A coastal town in ...
By Martin Doonan

Friday, 13 February 2009

Decisive moments and beyond

Final approach, Tanzania, January 2009

Some random links, that relate to timing in photography.

First from APOD: space station in the moon - a pre-planned decision moment.

I got sent this link to New York 2008 - a very interesting merging of the photographic and video. Particularly interesting is the way sequences seem to catch both the decisive moment of the traditional photograph and how that leads to the moment thereafter. Well worth watching.

A different view of wildlife

Giraffe spots, Tanzania, January 2009

Following on from thoughts and comments at Stills, I'm wondering why wildlife photography has to gravitate to the same styles? Whole animals, head up, looking at camera. Or for bird photography, the bird on a stick, full profile, clear eye. Certainly there are action shots of the dramatic but not too gory type, but it all starts to converge.

This seems to me to be the animal equivalent of the golden light, saturation to 11, Velvia-esque landscape stuff that I really don't care for.

Why can't we see more than the pretty picture in wildlife photography?

There is so much more to wildlife behaviour than that. I was fascinated by all kinds of stuff out in Tanzania - the way different species demonstrate relationships, and inter-relate with one another. Societal order, dominance and fighting. Feeding, preying, scavenging. Markings and camouflage.

In future, if I'm going to be photographing wildlife, in the wild, those will be the subjects I'll be looking towards: the interesting (to me) stuff.

Sunday, 8 February 2009

Photobooks categorized

I realised that I was putting together a lot of posts on photobooks, especially tips on how to do it. Thus I created a category and have gone back and labelled a whole bunch of posts. With SoFoBoMo drifting closer, maybe this will be useful to some readers out there.

Saturday, 7 February 2009

Safari workflow

Top table, Tanzania, January 2009

I thought it would be worth writing about my workflow while I was on safari. There are a couple of reasons for this, firstly I was using a fairly unusual set-up and secondly it generated quite a lot of interest from my fellow travellers.

The hardware

I was using my new Asus Eee PC netbook, a pair of external hard discs (Freecom Mobile Drive XXS) and a basic card-reader.

The software

Normally my primary download software is Breeze Systems' Downloader Pro. Due to user error (I forgot to update the license) I only had use of it for 1 day.
I also had Lightroom 2.2 installed.

OS is Windows XP Home.

My process

As I carried a limited amount of cards (16GB of CF), I needed to download all my images daily. Ideally that would all happen through Downloader Pro so I get automatic renaming. My normal alternative renaming software is RenameMaster but I've not installed it yet (another oversight on my part).

What I actually did was to use Windows Explorer to copy of the cards and Lightroom to rename & catalogue. I tried a few options but the one that worked best was to create a new catalogue for each day for the cataloguing and then merge that with a trip catalogue once all the pictures were sorted. My overall trip catalogue was broken down into daily folders for ease of selection.

As my Eee PC only has a 16GB SSD, all downloading was to a mobile drive. Once all downloads and naming was complete, I ran AllwaySync to back-up to the second drive. I only plugged in the second drive for the period of the back-up, this in order to minimise any risk of corruption etc.

How did it all perform

Downloader Pro is definitely the most efficient download & rename route. It seems to run faster than Explorer for downloading and automatically renames in that time. I certainly noticed a difference after the first day when I was no longer able to use it. Lightroom is a bit slow, because it is generates the catalogue and previews as it goes. I tried, briefly, to use it for the downloading as well - that was a complete disaster. the whole process took more than twice as long that way. As it was, the entire process, from initial download to back-up and card reformatting took about 1.5-2h each evening. I would let Lightroom do its thing during dinner.

The Eee PC is just about powerful enough for all this. The SSD makes it seem much faster that the processor spec. Even with all the extras running (card reader, hard discs) I get about 6h battery life. This meant I could use either the power tent, or run from my own tent. I ended up doing my preliminary shot ranking after dinner in my own tent. When running without USB devices or WiFi, I get a good 8h battery life.

Lightroom runs acceptably fast on the netbook. It does require a little more patience in scrolling through lots of images and I did no editing, just cataloguing. Even so, it never hung-up or failed even on battery power. The install size I quite modest, which makes it ideal for travel like this. Using a separate catalogue for each day's download seemed to speed things up. It was a trivial task to then merge with the main catalogue. Had I not needed Lightroom for renaming, I would have skipped this step.

As ever, AllwaySync just got on and did it's thing. It's fast and reliable. I tended not to run it as a background process as I do at home so that I got maximum performance out of every application at each step.

What would I do different

For sure, I'll make sure Downloader Pro is good to go in future. Lightroom is just too slow for downloading and renaming.
I would also be tempted to have many more CF cards. That way I could use the CF as the primary storage and the hard drive(s) as back-up. That would mean carrying around 100GB for such a trip. Even if I didn't have a full complement of CF cards, it would mean I could run cataloguing every second day.
Obviously, carrying any form of computer requires access to reliable power. Having a generator in the camp helped a lot. I won't be getting rid of my mobile viewer, it's invaluable for more remote travel.

Thursday, 5 February 2009

Some advice for photographic safaris

The big lens in action, Tanzania, January 2009

Based on my recent trip to Tanzania with Andy Biggs, here are some pointers from a traveller's perspective. This was my first such trip, so this post is more geared towards the new-comer, as ever YMMV.

First, get to know your camera. I was surprised that people weren't fully familiar with the functions of their camera. They have expensive gear and don't know how to use it to its best. Out on safari is not the time to learn. Based on what I experienced, these would be my top things to learn (this should all seem a bit basic):
RAW shooting, Av & Tv, metering and compensation, depth of field control, servo focus, thumb focus button, ISO setting & auto-ISO, panning & tracking subjects, manual exposure.

Learn to fine tune the custom settings to your preferences.

If any of that doesn't make sense, or is new I suggest spending some quality time with your camera and its manual.

Second, equipment selection. There's quite a bit of advice out there, some of it designed to scare you that you'll never have enough equipment, some suggesting you can get by with very little. I'll tread a middle course.

The cameras: you'll need more than one body (I automatically assume you're a DSLR shooter). This is not for back-up purposes. The primary reason is so that you can mount multiple lenses and switch quickly - you will not have time to mount and un-mount lenses frequently if your subject is moving. Having similar operation helps a lot. For reference I had a Canon 20D and 40D; these are sufficiently different in operation that it was often a problem switching (buttons and functions in different places). For a general 3-lens set-up, I'd highly recommend 3 bodies, one for each lens.
The lenses: I reckon a general 3-lens set-up is good. A mid-zom, mid-telephoto and long lens should be good. I took a 17-40, 70-200 and 500 plus 1.4x teleconverter. In future I'd drop the 17-40 and carry my 300 instead. A 24-105, 100-400 & 500 would also be a good combination.
Out on the plains you'll often want more focal length. The 500 + TC gave me 1120mm-e*, just enough for big wildlife on open plains. Birders may well want to longer. (If you are a birder it is worthwhile hooking up with others similarly inclined. Cat hunters and birders in a vehicle can make for some tensions.)
I found the wide-angle opportunities limited: that's usually landscape where I want a tripod, low-ISO, small aperture, long exposure. Safari is not conducive to that sort of work. You can't get out of the vehicle and often have to move quickly to get the the wildlife.
If you can't afford the extra equipment, rent. There are plenty of places that will rent the big glass and good bodies. Some on the trip had done just that. Better that than cursing missed opportunities.

The other kit: lots of memory. I reckon you can expect to take at least 500 frames a day, and up to 1500 on a good day. That means lots of storage required. Having enough CF cards is a good way to go, but may mean buying lots of cards that aren't otherwise needed. I used a netbook and a pair of external drives, with full duplication between them. I had originally estimated to shoot about 2500 frames total, around 40GB. That took 3 days. I was glad of the extra capacity, ending up with 5500 shots and 72GB. In the group, that was typical. Those with pro cameras were shooting as much as 20-30GB a day.
You'll also need spare batteries, chargers, cleaning kit etc. Supports (tripod/monopod) are a bit location and vehicle dependant. For our trip with enclosed Land Rovers with a pop top, they were useless. I was glad I left them behind. Binoculars can be useful, but don't sacrifice photo gear to carry them.
A good camera bag, preferably quite small so you can carry it in the vehicle. I was actually using a belt system for my bits and pieces, which I slung over the seat but that is unusual and means a lot of kit rationalisation.

Other stuff. Be patient. Often it takes time for a situation to develop. Sitting around watching lions sleep until they get up is necessary. Waiting for a leopard to climb out of a tree is an unmissable event.
Learn something about the wildlife and location, even if it is just watching a bunch of nature documentaries. Even a little knowledge goes a long way. Being able to identify major species is a must.

Non-headline features

Why is it camera companies don't see fit to publicise really useful features? Case in point, the EOS 50D, which I bemoaned a while back.

One of my safari companions had a 50D. Turns out it has 3 useful (for me) features. Some are in the manual, one isn't. They are:

Auto ISO from 100-1600. Compare with the ridiculous 400-800 of the 40D. This means with the 50D you can pretty much use auto ISO all the time.

Micro AF adjust (pretty sure that wasn't in the headlines). Nice for fine tuning lenses.

Fast buffer clearing with UDMA cards. Seems that even with RAW and a 16 shot buffer, the buffer clears fast enough that the buffer limit isn't constraining in practical use. With my 40D, I still bang against the 15 shot limit.

If Canon had seen fit to advertise that stuff, they'd probably have made a customer out of me. Now I'm considering it as an additional body but might wait for prices to drift downwards. Perhaps camera companies should publish the new manuals as part of the press release so we can really figure out what's what.

Wednesday, 4 February 2009

Scribus and POD output

I've just received my first Blurb book, formatted in Scribus and output in jpeg for inclusion in Blurb's Booksmart software. The book is a 7" square soft back, premium paper, printed in the Netherlands.

I came across an issue that is worth mentioning for others doing POD books.

My process was this: create all the layout in Scribus to correct sizes, export all pages (including text) as high quality jpegs, import these jpegs into Booksmart using full-bleed image layout. This way I get all my layout & fonts without having to worry about Blooksmart options. Simple and hopefully effective.

What happened? I received the book pretty quickly. First inspection is that this is a quality product: it's nicely bound, the paper has a good weight to it and the black and white is truly neutral. So far, so good. But closer inspection revealed very poor printing - jaggies and aliasing on all the diagonals and details. Ugh!

I trawled the Blurb forums for evidence of similar problem, nothing doing. However, before racing off to complain at Blurb I decided to double check the input files for a comparison. It turns out this problem is entirely user generated (i.e. my fault).

The problem is this: the output jpegs from Scribus are of pretty low quality. Despite setting high quality compression and 300dpi, the base jpegs look like 100dpi (or lower) versions. Not good. I wondered what had happened, so I did a few trials.

It turns out that when exporting pages from Scribus as jpegs, it uses the preview quality as the basis for generating the output, not the base image quality. I had been using medium preview quality for program speed throughout the process of generating the layout. Thus, the jpegs that were output had very low resolution quality. On switching to full quality previews, the jpeg output is as it should be. This is entirely different behaviour to the pdf output, which always uses original image quality for output.

Needless to say, I'll be reordering but I'm pretty confident results will be very good this time around.