A guy walks into a camera store…..

Perhaps by the time I finish this post I will think of a punch line. I did actually walk into a camera store today and was handed a lens to look at to see if I had an opinion as to what it was.

I’m assuming that may be due to my penchant for doing things with cameras and lenses that might not otherwise show up with an internet search. In any case I was also stumped at that moment. The lens is a Tamron adaptall 28-50 f3.5-4.5 Close Focus lens with 9 elements, actually 10 as your about to see. That info all shows up on the Google machine but what doesn’t is the apparent modification its received. In the center of the lens is a big yellow dot or to be more precise an additional lens element that only impacts the center of the image.

So what does this mean for the final image? Well it acts like two separate lenses to form one image. The outer area being the original lens which focuses as per normal to form an image at the film plane while the center forms a second image that would be in focus at a different distance but as it reaches the film plane it is out of focus and combines with the outer areas image to give a combined soft focus image. I cant honestly say whether its supposed to be that yellow though. It could be intentional because it gives a warmness to the soft focus or on the other hand it might just have yellowed over the years.

In this little diagram above A represents the film plane where both images combine and B represents a different location where the central area would be in focus if the film was there instead.

So you might be wondering how can I be sure that’s what’s happening. I’m glad I pretended you asked. Because the final image is a combination of the outside area and the center and if you change the ratio between them you will get a different result. How? Alter the aperture, as you stop the aperture down the central area will comprise a greater amount of the overall image. Keep in mind the viewfinder image is formed with the lens wide open so the outer area is dominant and what you actually use to achieve focus.

Lens wide open at f3.5
Lens stopped down to f8
Lens stopped down to f16

The overall effect is accentuated by the fact I used a camera with an APS-c sensor rather than the full area of a 35mm film which would provide for more of the outer area to form the image. So that’s my conclusion its a 1980’s modified lens likely belonging to a wedding photographer intent on creating that look that every one wants and will never go out of style.

Okay here goes…A guy walks into a camera store and breathlessly says “Quick give me some Dektol!” The clerk perplexed asks what is the emergency? The guy says I don’t know but its a developing situation.

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