How to Calculate Near Focus Limit For Large Format Macro Photography
In this first article, I share how you can calculate the near focus limit for any of your shorter standard lenses. In the second article, I walk you through how you can calculate the required bellows extension for your large format macro photography projects. In the third article, I teach you how to calculate exposure compensation to ensure you are giving your film enough exposure in addition to some extra bonus tips to take your large format macro photography to a new level. If all of this sounds interesting, then you are in the right place. Let's get started!
How to Calculate Near Focus Limit For Large Format Macro Photography
I routinely use my standard or wide-angle lenses for landscapes (90mm, 120mm, 150mm) and if I come across a beautiful flower during my hikes, I can use the same lens to create some beautiful macro 1:1 or greater magnification photographs. I also love to do large format floral still life photographs as well. I should note that not all lenses perform the same at higher magnifications, so keep this in mind and if you need help deciding on an appropriate lens. If you have been following me for very long, you probably already know that I love to do a lot of flower photography. It has always been a passion of mine since I was very young. I continue to be surprised and mystified by the ethereal nature of flowers. I use all of these skills that I share with you in this series on large format macro photography on a daily basis as I create my large format botanical photographs.
Whether you are outside in nature or working in the studio, you probably already know that you need to manage three key concepts in order to create high-quality macro photographs with your large format view camera. First, you need to select a lens that is suitable for your desired magnification. To keep things simple, I will discuss 1:1 in these articles, but I will provide you the information to be able to calculate much higher magnifications such as 2:1 or even 3:1. Besides increasing exposure compensation requirements, a limiting factor of magnification ratio is often the bellows on your camera. Along with the optical considerations, you need to quickly determine if your camera has enough bellows extension to facilitate your goals. For example, if you have a very sharp 150mm APO lens and you want to create a 1:1 photograph of a beautiful flower for example, then you know you will need a minimum of 300mm of bellows for the 1:1 image. More on all of this shortly. Also, in addition to your lens selection and bellows extensions, wouldn't it be very helpful to know before you ever set up and get started with the near focus limit of your lens? Of course it would... Knowing how close the front element of your lens can be positioned in front of your subject is a key piece of information that will save you a lot of time. I am actively developing a large format photography resources page where articles like this are all centralized and easy to find. You will find this article on the main resources page along with a lot of other related large format information that I know you will find useful and helpful. HOW TO CALCULATE NEAR FOCUS LIMIT
In the section below, I will give you the formula to make this calculation. You really only need to go through this process one time for each of your lenses. I have a small cheat sheet that I have printed and taped in the back of my field journal with all of this information. Formula Legend F = focal length D = minimum distance to subject from the lens B = bellows draw on your camera For example, if I wanted to use my 180mm Nikkor lens for a 1:1 magnification of a flower, I would simply do the following calculation to determine my minimum focus distance: 1/F = 1/D + 1/B Using the 180mm lens for example: 1/180 = 1/D + 1/360 Hint: remember for 1:1 macro, we need two times the bellows draw of your focal length. Using basic algebra we can solve for the third variable when we know the other two. To solve for 1/D we take focal length minus our bellows draw 1/D = 1/180 - 1/360 Now I convert the fractions to decimals 1/D = .0056 - .0028 (.0028) Next, I solve for the final step by dividing 1 by .0028 by for a minimum focus distance of approximately 357mm (14 inches). If want to simplify even further, Chris Rusbridge has provided the following simplification: 1/D = 1/180 - 1/360 So what does all of this really mean and how do you use it in your large format macro photography? I am so glad you asked...
Now you can set up the front element of your lens at approximately this distance from your subject and then work through your normal routine and then proceed to the exposure compensation calculations which I share with you in the next article. That is all there is to it. So, do this for all of the lenses that you know that you may want to use for your large format macro photography and get out there and start using this information. I am actively developing a large format photography resources page where articles like this are all centralized and easy to find. You will find this article on this page along with a lot of other related large format information that I know you will find useful and helpful. LARGE FORMAT MACRO CHEAT SHEET For 1 to 1 (1:1) magnification for any lens, your bellows draw will be twice the focal length and the exposure compensation for this will be 2 stops. For 2 to 1 (2:1) magnification for any lens, your bellows draw will be three times the focal length and the exposure compensation for this will be 3 stops. For example, let's assume I want to use my 180mm Nikkor lens on my 4x5 view camera for some 1:1 close-up flower photos. I know my bellows extension will need to be 2X 180mm (360mm) and my exposure will be 2 additional stops plus what I metered, plus any filters. I will then apply reciprocity failure times for my film. New exposure = base exposure x exposure compensation factor + filter compensation and then a correction for reciprocity if applicable. Share your thoughts and comments in the section below. -Tim Layton
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Comments
Chris Rusbridge(non-registered)
Very useful set of pages Tim, thanks. Just a bit picky on this section:
"1/D = 1/180 - 1/360 Now I convert the fractions to decimals 1/D = .0056 - .0028 (.0028) Next, I solve for the final step by dividing 1 by .0028 by for a minimum focus distance of approximately 357mm (14 inches). " As it happenes in this instance it is easier to solve this exactly. We have: 1/D = 1/180 - 1/360 which we can rewrite as 1/D = 2/360 - 1/360 1/D = 1/360 D = 360 mm
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