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A question on equivalence...

crashwins

New member
I've been a working photographer (side-hustler) for a while..One of my favorite photographers (focuses on enthnographic work, nonprofits, lifestyle) uses an IQ250 and a 55mm for like 95% of his work...I find that very interesting as I lug around 3-4 lenses for my Nikon or Sony bodies. I'm in a creative lull and have considered trying to pair down my gear and my "work" for what I find more enjoyable -- portraits and simple landscapes. I realize changing my gear won't make me a much better shooter -- it's not that. But some gear does inspire. So I've contemplated switching to a fast prime and trying to stick heavily to that as it might force me into something more creative, think more on lighting, post, etc. Here's my question:

On the IQ250 or a 645Z the 55mm looks like a 43mm in terms of field of view, no? The .79 multiplier is a 43mm F2.2 lens. But in 35mm terms what looks more like this in terms of compression, angle of view, etc -- a 35mm or a 50mm? There's a "look": it has the right amount of background compression (not that "swimming in bokeh" crap) and limited (maybe none) facial distortion. Any thoughts? Here are 2-3 examples. Thanks!

Screen Shot 2019-05-06 at 9.53.36 AM.jpgScreen Shot 2019-05-07 at 10.25.36 AM.jpg
 

dchew

Well-known member
Sometimes I wonder if the “medium format look” most people ask about is simply the 4x3 ratio. The 55mm is exactly the diagonal of the 44x33 sensor on the IQ250. Without taking into account the difference in crop ratio, the equivalent lens would be a 43mm, which is just about in between your 35 / 50mm options. If you crop the sides of the 36mm frame down to 32mm to get the 4x3 ratio, that would be a 40mm view, which is a little closer to the 35mm lens than the 50.

One thing you could try as a test: shoot the 35mm lens on your Nikon/Sony cameras and crop the image down from 24x36 to a 21x28mm size. That would give you the direct equivalent. See how you like that angle of view.

The “compression” part of your question is related to camera position, not really focal length.

Dave
 

MGrayson

Subscriber and Workshop Member
While every choice of sensor and lens has its own look, 98% of what you're seeing are the photographer's choices in lighting, position, aperture, post-processing, and, most importantly, relation to subject and timing.

Dave's suggestion of just taking a 35 with you is a good one. Experiment with settings and distance to your subject.

Enjoy!

Matt
 

Godfrey

Well-known member
The 'coupling' between FoV and DoF changes for every format. Getting just the right amount of background blur* as well as the right perspective depends a lot on what a particular format offers in focus zone control.

As the FoV gets wider, a larger format enables more focus zone control: the ability to make the DoF appropriately shallow to net that right amount of blur in the background without it turning to total mush. Narrower FoVs work better on smaller formats because on larger formats you can't grow the focus zone enough without stopping down the lens so far that exposure times become too long and problematic. Et cetera. So there is no such thing as "true equivalence" .. there are only approximations. Every focal length/format pairing nets a FoV and a range of DoF possibilities that you have to learn how to exploit for their good qualities and how to workaround for their limitations.

For example, I have been particularly obsessed with the look of images made with the Hasselblad SWC and its Zeiss Biogon 38mm f/4.5 lens on 6x6 film. Calculating the FoV for different formats with different focal length lenses has netted a range of interesting equivalents camera (format) and lens possibilities, and I've tried them all. In testing and experimenting, there's getting the FoV right (which includes the square framing), there's getting the DoF right (which involves figuring out what f/number nets the same focus zone as the SWC), and then there's getting the actual rendering qualities of the specific lens being used to be a close match to the Biogon 38. I've found several pairings that work well and provide a close equivalence (or simulation) of lens qualities and FoV, but with smaller formats (FourThirds, APS-C, and FF) I can't get the same amount of subtle background blur (DoF) at useable aperture settings. This is one of the reasons why I'm moving up to medium format digital for my ultra wide work: 33x44 format sensors cropped square will net focus zone control only a stop and some down from 6x6, not the two to five stops for FF, APS-C, and FourThirds. It will never be exactly the same, but I think it will finally be that satisfying equivalence I've been looking for. I'll know in a couple of months. :D

I fully support Dave and Matt's notions: Fit the lens that is closest to the FoV you want on your chosen camera and go experiment, see what you can get out of it. For instance, my Summilux 35mm f/1.4 v2 on a FF format M or SL produces one range of FoV-DoF couplings, and with my APS-C CL body, a different range ... depending on focus distance and aperture. Both are great when used appropriately for a particular subject I'm working on—the only way to know when to use what is to experiment enough to know what works for what I want to get. :)

G

* Bokeh isn't "the amount of background blur." Bokeh is the quality of the blur and applies to any amount of blur. I see the word bokeh used incorrectly like this all the time, but it's best to think of it more precisely if you want to be able to understand and control your imaging. Bokeh for any given lens varies on the basis of distance setting and aperture setting, and even subject type has an effect on it. Experiment with different settings, distances, and subject types to fully understand what the bokeh of a particular lens will be.
 

dougpeterson

Workshop Member
Background blur." Bokeh is the quality of the blur and applies to any amount of blur. I see the word bokeh used incorrectly like this all the time, but it's best to think of it more precisely if you want to be able to understand and control your imaging. Bokeh for any given lens varies on the basis of distance setting and aperture setting, and even subject type has an effect on it. Experiment with different settings, distances, and subject types to fully understand what the bokeh of a particular lens will be.
I don't know. I think there is some room to consider quantity of blur as an aspect of bokeh. One can reasonably say that bokeh refers to the visual characteristics/quality of out of focus subject matter, and as they say: "Quantity has a quality all its own"
 

Godfrey

Well-known member
I don't know. I think there is some room to consider quantity of blur as an aspect of bokeh. One can reasonably say that bokeh refers to the visual characteristics/quality of out of focus subject matter, and as they say: "Quantity has a quality all its own"
If you conflate quality of the blur with the amount of the blur, the meaning of the word bokeh is lost, at least when you are using it to describe the differences in the blur that a specific lens can produce at different focus settings, f/number settings, and on different scene types.

Kept separate, you can say things like "Given this subject and this focus distance, the bokeh of the Nokton 40mm f/1.4 is a bit jarring, but stop the lens down to f/2.8 and the bokeh becomes nice and smooth. The amount of blur is a bit less, but the bokeh produces a more pleasing separation effect with the critical focus plane without the jarring doubling of the straight line patterns in the scene."

It's a point of precision in the use of language, to me.

G
 

Shashin

Well-known member
35mm or 50mm is a tough one. Both are subtly different from 43mm, a normal on a 35mm camera. The 35mm will give you more apparent perspective, making things look a little more dimensional. The 50mm will compress the apparent perspective a tad. The 50mm would be more classical: 19th and early 20th century photography bias toward longer than normal. On 35mm, I have always gone with the 35mm. But being spoiled with normal lenses on other formats, the 35mm is not quite it. A 50mm for me is a little constrained compared with a normal.

However, there are a few 40mm lenses available for 35mm. Tamron makes one with a good reputation. Voightlander has a manual focus 40mm. Personally, I would go for one of those.
 

Shashin

Well-known member
I don't know. I think there is some room to consider quantity of blur as an aspect of bokeh. One can reasonably say that bokeh refers to the visual characteristics/quality of out of focus subject matter, and as they say: "Quantity has a quality all its own"
Bokeh is just the aesthetic quality of the out of focus area of the image. It is not depth of field, which would be corresponding to the quantity of the area that is out of focus. But regardless of how much DoF is in the image, it is the quality of that out of focus area that is referred to with bokeh. I had my first lesson in this by the lens designer at Minolta when we were releasing a lens the was optimized for the quality of the bokeh. So I you can say that two characteristic distinguish the out of focus area: Depth of Field and Bokeh. Each define different aspects.
 
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