Hermagis, objectif pour vues

This lens consists simply of an achromatic doublet, produced by Hermagis, a French optician in business since 1845. It dates probably from 1850’s or 60’s. Its constructive principle is the same of lenses used by Nicéphore Niépce and Louis Daguerre for the very first photographic images. Due to its simplicity and easiness of construction, lenses of this type remained in production for many decades, favored by faster emulsions and popularization of photography in cameras aimed to amateurs.  read more


Rapide nº 4 de Derogy, using a Petzval type portrait lens

Derogy - Rapide n4 - Petzval typeWith modern lenses it is possible to focus on any part of an image and get a sharp spot while keeping composition as it please us. With old lenses, Petzvals for instance, even adjusting the best focus, the peripheral parts of an image will never come out sharp, unless we stop down the lens. This article discusses how to use a large-format camera for situations where the subject we want sharp is far from the optical center of the lens and we want it fully open. read more …


Lens front raise online simulator

In some cases, it might be interesting in architecture and urban photography, to keep buildings’ vertical lines parallel in the picture as they are in reality. Well, you know, you can give a lens front raise for that. But will your lens/format have room enough for that? How much can you raise it? Where will the horizon line end up? Check out this online simulator. read more…


Using a Petzval lens for potraits

Using Petzval-type lenses for portraits when the subject's face is out of the center of the image requires some care. The article discusses and gives an example of how to decentralize the lens to reposition its optical axis over more peripheral areas of the photographic frame.

Mix your formulas – black and white...

Find a compact set of chemical reagents, 8 in total, that will allow you to develop film and print B&W photographies. With instructions about mixing, using and cost considerations. A nice starting point if you are interested in setting up a photography darkroom and make your own chemicals.

Enlarger head using LEDs

Article presents project to build a black and white photo enlarger head, with timer, using LEDs and Arduino platform. The result is high power and excellent contrast control for black and white work.

Using RAW format in photography

Article analyzes a practical case in which the use of RAW file, thanks to its greater depth of color, allows the exploration of areas of a photograph that in format .jpg would be lost.

Color Depth in digital image files

Article explains why and how color-depth concept is necessary to express the array of different colors a digital system can handle. It clarifies why it must be expressed in bits, what that means in terms of color differentiation, when true-color is reached and why sometimes more than true color...

Finding the focal length of a lens

  This is a calculator that will help you in finding the focal length of a photographic lens. The method is about focusing on one or more objects at different distances. Each time, you write down 3 measurements: Object size Image size How much did you advance the lens from infinity position in...

Pinhole, where truth, beauty and goodness...

Pinhole is a photographic technique that employs most of the times a home made camera in different degrees of improvisation and roughness. Matchboxes, shoeboxes and whatever boxes and containers are sort of starting point for those projects. The photographer bricoleur may also start from scratch by...

Front raise and horizon line

For a given lens and given film or sensor format, this simulator shows how much it is possible a front raise and where the horizon line will end up in the final picture. Focusing is assumed to be at, or closer to infinity, a normal landscape condition. Observations: 1 – The scheme is...

Refraction, Dispersion and Optical Glass for...

Refraction Refraction is a phenomenon of waves changing direction when passing from one medium to another. In a photographic lens that is the case when passing from air to glass and again from glass to air. It occurs also when passing from one type of glass to a different one. They are not all the...