Date an old photograph ? , this page may help you.
Below is a list of links to photographic processes and links to sites which I’ve used over the years, to help date my old photographs. These maybe helpful to you when you need to date an old photograph, if you are tracing your family tree, and have old photos of family members you are not sure of.
OLD PHOTOGRAPHIC PROCESSES

Photo Credit -commons.wikimedia.org/wiki/File:Harvard_Daguerreotypes_-_sAg_168.70.1.jpg
http://www.phototree.com/id_dag.htm
https://blog.scienceandmediamuseum.org.uk/find-out-when-a-photo-was-taken-identify-daguerreotype-photography/
http://www.graphicsatlas.org/identification/?process_id=366

Photo Credit – commons.wikimedia.org/wiki/File:William_Henry_Fox_Talbot,_View_of_the_Boulevards_of_Paris,_1843.jpg
https://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/atlas_saltprint.pdf
http://www.graphicsatlas.org/identification/?process_id=269

Photo Credit – commons.wikimedia.org/wiki/File:-Collection_of_British_Calotypes_and_Wood-engravings-_MET_DP70833.jpg
https://www.loc.gov/rr/print/coll/589_calotype.html
https://www.gla.ac.uk/myglasgow/specialcollections/collectionsa-z/hilladamson/calotypeprocess/

Photo Credit – commons.wikimedia.org/wiki/File:Anna_Atkins_Cystoseira_granulata.jpg
http://www.graphicsatlas.org/identification/?process_id=319
https://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/atlas_cyanotype.pdf

Photo Credit – commons.wikimedia.org/wiki/File:Ambrotype_of_a_baby_with_cuttings_of_hair_under_the_glass_(3588772191).jpg
http://www.phototree.com/id_amb.htm
https://blog.scienceandmediamuseum.org.uk/find-out-when-a-photo-was-taken-identify-collodion-positive-ambrotype/
http://www.graphicsatlas.org/identification/?process_id=283

Photo credit – commons.wikimedia.org/wiki/File:Early_portrait_of_a_rather_plump_Victorian_gentleman
http://www.graphicsatlas.org/identification/?process_id=352

Photo Credit – commons.wikimedia.org/wiki/File:Group_portrait,_family_of_five,_Cased_tintype,_half_plate.jpg
https://blog.scienceandmediamuseum.org.uk/find-out-when-a-photo-was-taken-identify-ferrotype-tintype/
http://www.graphicsatlas.org/identification/?process_id=280

Photo Credit – commons.wikimedia.org/wiki/File:Queen_Victoria.jpg
http://www.phototree.com/id_cdv.htm
https://blog.scienceandmediamuseum.org.uk/find-out-when-a-photo-was-taken-identify-a-carte-de-visite/

Photo Credit – commons.wikimedia.org/wiki/File:Arch_of_Titus_by_Romualdo_Moscioni._Albumen_Print.jpg
http://www.graphicsatlas.org/identification/?process_id=143
https://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/atlas_albumen.pdf

Photo Credit – commons.wikimedia.org/wiki/File:%C3%89tienne_Carjat,_Portrait_of_Charles_Baudelaire,_circa_1862.jpg
http://www.graphicsatlas.org/identification/?process_id=38
https://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/atlas_woodburytype.pdf

Photo Credit – commons.wikimedia.org/wiki/File:Chester_A_Arthur_Cabinet_Card_by_CM_Bell,_1882.jpg
http://www.phototree.com/id_cab.htm
https://blog.scienceandmediamuseum.org.uk/find-out-when-a-photo-was-taken-identify-a-cabinet-card/

Photo Credit – www.goodfreephotos.com/spain/other-spain/the-library-and-the-chapter-at-the-cathedral-collotype-1889-in-santiago-de-compostela-spain.jpg.
http://www.graphicsatlas.org/identification/?process_id=26
https://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/atlas_collotype.pdf

Photo Credit -commons.wikimedia.org/wiki/File:Alfred_Stieglitz_-_The_Last_Joke_Bellagio,_1887.jpg
http://www.graphicsatlas.org/identification/?process_id=271

Photo Credit – commons.wikimedia.org/wiki/File:Werner_Haberkorn_-_Via_Anchieta._S._Paulo_a_Santos._panorama_Fotolabor_-_53.jpg
http://www.graphicsatlas.org/identification/?process_id=303

Photo Credit – commons.wikimedia.org/wiki/File:Frederick_Douglass_LOC_collodion_c1865-80.jpg
http://www.graphicsatlas.org/identification/?process_id=222
https://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/atlas_collodion.pdf

Photo Credit – www.graphicsatlas.org/identification/?process_id=104
http://www.graphicsatlas.org/identification/?process_id=104

Photo Credit – commons.wikimedia.org/wiki/File:Model_in_New_Look_fashion_on_steps_of_the_Public_Library_of_New_South_Wales,_1950__silver_gelatin_photoprint_by_Rob_Hillier_(7785514320).jpg
http://www.graphicsatlas.org/identification/?process_id=266

Photo Credit – commons.wikimedia.org/wiki/File:Aubrey_Beardsley_LCCN95500934.jpg
http://www.graphicsatlas.org/identification/?process_id=125

Photo Credit – commons.wikimedia.org/wiki/File:Hb_3343412.jpg
http://www.graphicsatlas.org/identification/?process_id=343

Photo Credit – commons.wikimedia.org/wiki/File:Andrew_Jackson-Related_Collodion_Print_Photographs,_1897_(4359293217).jpg
http://www.graphicsatlas.org/identification/?process_id=296

Photo Credit – commons.wikimedia.org/wiki/File:Emma_Barton_-_The_Awakening.jpg
http://www.graphicsatlas.org/identification/?process_id=306

Photo Credit – commons.wikimedia.org/wiki/File:Postcard._Greetings_from_the_dear_Homeland._Wildt_and_Kray,_London,_N.W._Series_no_1819._Printed_in_England._(1910)._(21643308556).jpg
https://blog.scienceandmediamuseum.org.uk/find-out-when-a-photo-was-taken-identify-a-postcard/

Photo Credit – loc.gov/pictures/resource/ggb
http://www.graphicsatlas.org/identification/?process_id=364

Photo Credit – commons.wikimedia.org/wiki/File:Accession_Number-_1982-2070-0002_(2678237668).jpg
http://www.graphicsatlas.org/identification/?process_id=301

Photo Credit –
Alfred Roller (1864–1935) 1909 © Madame d’Ora (1881–1963) Arthur Benda (1885–1969)
http://www.graphicsatlas.org/identification/?process_id=347

More can be found
http://www.graphicsatlas.org/identification/?process_id=326
CLUES IN OLD PHOTOGRAPHS
What Are They Wearing.
https://blog.findmypast.co.uk/family-photos-what-are-they-wearing-1406240689.html
Dating Vintage Photos.
https://www.worthpoint.com/articles/blog-entry/dating-vintage-photographs-1840-2
Vintage Fashion.
https://vintagefashionguild.org
Fashion Expert.
Genealogy.
http://www.internet-genealogy.com/Dating%20Old%20Photos.pdf
Identify Old Family Photos.
http://thephotoorganizers.com/dating-identifying-old-family-photographs/
Old UK Photo.
http://www.cartes.freeuk.com/time/time.htm