Possible sources and problems researching 17thC dress in Norway
What sources excists for 17thC dress are probates,written material from the time, paintings and memorials in churches ,extant garments and folk costumes from some of the inland and midland regions.
Probates are an excellent source of what was worn in the rural regions in the 17thC. But as most authors who've spent time dwelling in archives agree on, the descriptions vary a bit and it's not always easy to ascertain what was being described. 17thC probates have different names for types of bodices and stays even within the same region.
Private letters and books of the time is another potential source.
Most of the pictorial evidence from the 17thC are of the high echelon clerks and officials, priests and the wealthy. And of course of the court in Denmark. There is a rare exception from 1699  of a wealthy farmer with the first and the second wife. Compare this to Johanne Engelbrettsdatter from 1695. (The prune look is caused by the paint cracking). 
The fashion among the powerful and wealthy in the towns are known to differ very little if any from what was worn in Europe and the dutch region. It's natural to look to Denmark, the Netherlands and England for a comparisson. The dutch influence is evident even today. The danish fashions would also have a marked influence in the towns due to the king and court being in Denmark.
A marked difference between town and rural dress emerges about mid 17thC. This leads to a already conservative rural populace stagnating fashionwise. The 17th C sees a bit of upheavels in Scandinavia. Denmark had a few rather disasterous wars going with Sweden during the first half of the 17th C. The end result being the loss of parts of  Norway and Skåne to Sweden.
Using folk costumes as a source of 17thC dress has its challenges. Tweaking out the later additions and figuring out what has been altered. The first step then would be to pinpoint specific changes in tailoring, materials and possibly color.
New embroidery patterns might be added. Some regions had a strong dislike of the color green which overruled current fashion colors, while absorbing the garment. Embroidery patterns known from a german sampler from 1550 is still being used with few alterations today on some costumes.
A lot of 16thC headlinen styles survives almost totally unchanged for close to 500 years. Mostly embroidery is added if any changes are made. 16thC styles of headlinen are easy to spot. Or rather most of them are. There are styles that might have originated about 400-600 years earlier, but it's as likely that these styles were "reinvented" in the 16thC. Comparison with german paintings of the time makes it likely that this type of embroidered headlinen is of early to mid 16thC origin. While the pleated headlinen leaves no doubt of origin.
Folk costumes with strong elements of 16thC dress survived in everyday use untill the end of the 19thC. Later for the oldest generations. What is certain is that folk costume was still being used at least as late as the 1930s as everyday garb among the older women in some rural regions.
Different regions adapt different newer fashion traits due to various outside influences. Some regions have the men working as sailors or soldiers in other parts of Europe. The new priest might have a wife who brings in newfangled ideas. Whitework embroidery (known as Hardanger embroidery today) being brought into at least one valley that way mid 17th C.
Along the way, elements of power dress got incorporated into the folk costumes. The 16th and 17th C having a very strong influence on womens clothes, while the 18thC and 19thC seems to have had the strongest influence on male costume.
From the 16th and the 17thC womens dress have incorporated the silk embroidered linen shirts, stays, aprons, the flasque jackets (jackets with skirts), mittens and gloves ,knitted stockings and nightshirts.
Aprons in the the rural regions were according to probates of the later part of the 17th C mostly made of wool. White ones are mentioned .
The origin of the embroidered shirts are undoubtedly the shifts and shirts of the mid 16th to early 17th C wealthy and powerful . There are some distinctive differences in style of embroidery and choice of colors among the regions which have maintained these shirts as part of the folk costume. Some regions have kept the blackwork collars of the 16th C.
As a curiosity, Norway has probably one of the bigger extant collection of 17thC knitted silk nightshirts known today. The nightshirts were known to be used under the stays in the rural districts. In Skåne(Skandia) in Sweden, some folk costumes have retained the knitted sweater as part of the folkcostume. Worn under the stays or rather a bodice. Setesdal in Norway has maintained a knitted sweater as part of the male costume. The pattern is basic blackwork patterns from 16th C in charcoal and natural white. 
During the 18thC the stays have either changed to a barly boned or unboned bodices or become the corsette in high fashion clothing. The tailoring of the backs of jackets change according to fashion in some regions. The little flaps on the shoulders from the 17thC is often kept as an essential part of the jacket. Many jackets still maintain a 16thC cut in front. With or without 16thC embellishment on the lower sleeves.
The 18thC sees the biggest change with new fabrics and embellishment. Metal bobbin lace is mostly a 18thC addition in the rural regions. The brocade and metal lace seen in use on folk costume mostly stems from the traveling salesmen making a living walking across large parts of the county on foot.
The 19thC is the definite death of boning in folk costume. Early 1800s sees a new very popular fashion emerge and hardly any folk costumes can be said to have withstood the onleash of the cropped jacket and short waist of the "empire"fashion. The middle of the 19thC is more or less the end of folkcostume in regions closer to the bigger towns.
Skjaak church 1642
1666 danish
1660s dutch
17thC rural Norway
1695 Johanne Engelbrettsdatter
1699 detail from painting of wealthy farmer with family
References (list not finished)
Updated 10th of august 2005