Certified Professional Photographer Exam question

[indraneel]

<blockquote>

<p>but perhaps they intended it that way to make sure that person taking the test truly understands how focal lengths operate in different formats</p>

</blockquote>

<p>In my experience most tests test for people's capacity to understand other people's intentions, rather than technical knowledge. It's nearly impossible to design tests that will not be subject to misinterpretation. So, so far as what tests actually test for, this question was a good test of "professionalism", assuming that professionals usually have to read other people's minds, specifically their clients'.</p>

[leighb]

<blockquote>

<p>Uhm... <em>and</em> conjugate distances.</p>

</blockquote>

<p>The question as originally posted says<br>

"If focusing on the same subject at the same distance,..."</p>

<p>This disregards some very minor issues such as the location and separation of the principle planes, which would make trivially small differences in the film position.</p>

<p>- Leigh</p>

 

[steve m smith]

<blockquote>

<p>This disregards some very minor issues such as the location and separation of the principle planes, which would make trivially small differences in the film position.</p>

</blockquote>

<p>If it's the same subject, distance and focal length, how does the format affect image size?</p>

[leighb]

<blockquote>

<p>If it's the same subject, distance and focal length, how does the format affect image size?</p>

</blockquote>

<p>It doesn't. That's what I said previously.</p>

<p>The point is that different lens designs may affect the position of the film relative to the first principle plane, so if you measure the distance from the subject to the film it may differ a bit for different lenses.</p>

<p>For example, a 300mm lens designed for a 35mm camera would likely have a different optical configuration than a 300mm lens designed for a view camera. This can change the position of the image plane relative to the subject. </p>

<p>The difference is very small, but probably not zero.</p>

<p>- Leigh</p>

<p> </p>

[graham_martin2]

<p>Perhaps someone can help me out with the Definition of "image size". Let's assume that the subject is a box with a wall behind it, and that using a 300mm lens on a 35mm camera, the box fills the frame. The resulting print will be of the entire box. If I were to put a 300mm lens on a MF camera then wouldn't the box no longer fill the frame? Would not some of image of the wall also be projected onto the negative/sensor and resulting print? Conversely, if the 300mm lens were used on a DX camera, with 1.5 crop, then only a part of the box would be in the frame and subsequent print.<br>

I bow to the wisdom of others on this forum, but where am I making my mistake?</p>

<p> </p>

[leighb]

<p>Hi Graham,</p>

<p>The size of the box ON THE NEGATIVE would be exactly the same regardless of the camera in use, for the same lens focal length. If the film is large enough, some of the wall would appear on it. But that's a function of film size, not of lens focal length. Refer to my post above about cutting a small piece out of an 8x10 negative.</p>

<p>The size of the image on the final print is a totally different and unrelated topic, dependent on the printing system in use.</p>

<p>And the "1.5x crop factor" is an abomination that should have been outlawed when first introduced. It's a source of endless confusion, and absolutely meaningless in the optical sense.</p>

<p>- Leigh</p>

 

[graham_martin2]

<p>Leigh</p>

<p>Thanks for helping to turn the light bulb on. I have been thinking all along about negative/sensor size. If I am understanding you correctly, if the camera didn't have any film/sensor, (and the image was being projected onto a piece of white paper inside the body) then the image would be the same size regardless of the camera body. I am assuming that the focal plane would be at the same distance from the lens mount. Am I on the right track?</p>

[leighb]

<p>Exactly. </p>

<p>Suppose you put the lens on a tripod all by itself with no camera body, and projected the image on a wall. </p>

<p>You can tape any size piece of paper anywhere in the image circle, and it will show whatever is appropriate.</p>

<p>- Leigh</p>

 

[graham_martin2]

<p>Thanks Leigh. That makes all the sense in the world. Now I can pass the exam!</p>

[g_k7]

<p>Doctors, lawyers, architects, accountants, veterinarians, dentists, pilots...I consider those "professions".</p>

<p>A photographer? The tent is vast and varied, but by no means would I call it a profession.<br>

Professional? What does that really mean?<br>

I picked "C" right away because it's not A nor B, and D isn't quite correct either. The actual image is the same no matter what, the film format just serves as a cropping factor of whatever image circle is projected onto the film plane.</p>

[eric merrill]

<p>Another way of stating this is that it doesn't matter what you capture or what you ignore, a 300mm lens is a 300mm lens.</p>

<p>That said, this is a good type of question that shows the "value" (or lack thereof) of certification for photographers. I bet most clients wouldn't care if their photographer could correctly answer this or not. I consider it to be a photo trivia. Fun stuff to think about it, but absolutely has no bearing on the quality of prints a photographer can produce.</p>

<p>It's easy to dispute my view of this certification. Just start asking potential clients if they care. :)</p>

<p>Eric</p>

[Lou_Meluso]

<p>Adrian, no disrespect, or sermon meant. It's a commonly misunderstood segment of the photographic world. Just a point of information. Tests like the ones the OP experienced are fairly common.</p>

<p>CK, your own interpretations not withstanding, a professional photographer is one that make his living from photography as opposed to an amateur photographer (or pilot for that matter) that pursues the activity for pleasure. </p>

<p>Apologies to you, Graham, for my off topic comments.</p>

[AlanKlein]

<p>Very enlightening discussion. So let me take it from the other end. When people say that using let's say a 50mm lens from a 35mm camera on a m43 format gives you <em>the advantage</em> of double magnification (acts like 100mm lens) because m43 sensor has a 2x crop factor, it's not that the lens is magnifying 2x. What's really happening is the same size image is being projected on the back of the m43 camera but because the sensor is 1/2 the size (on each side) of a 35mm digital sensor equivalent, you're getting what appears to be double magnification because the sensor crops the 35mm to see only 1/2 its size.</p>

<p>But effectively you would get the same thing on a 35mm sensor image file just by cropping the image 1/2 on each side in post processing (assuming the sensor has 4 times the pixels.)</p>

<p>Am I understanding this right? If so, I finally understand what everyone is talking about with 2x crop factor. </p>

[leighb]

<p>Hi Alan,</p>

<p>That's correct. You're just expressing the angle of view, which is a function of the sensor size.</p>

<p>- Leigh</p>

 

[ondebanks]

 

<p>Dennis,</p>

<blockquote>

<p>I guess I will never be certified. I have zero experience as a professional utilizing 35mm equipment and I have never run a comparison test with, or between, any equipment -just because- in my life. Darn. Another club I won't be a member of.</p>

</blockquote>

<p>You don't need to have ever used a 35mm camera (or a medium format camera for that matter) to correctly answer that exam question. That's the whole point. It is a test of comprehension of very basic optics, not necessarily of experience. The question is probing this: Does the photographer understand how a given lens focal length will form an image of a given subject? I think you probably do and you probably would have answered the question correctly, despite your lack of 35mm experience.</p>

<blockquote>

<p>Ironic isn't it that models show professional status through the work- even the U.S. government goes by tear sheets- yet the purveyors of this exam evaluate photographers based on math questions.</p>

</blockquote>

<p>Although I used a formula to "prove" the answer, I don't regard it as a math question. Look at it this way: unless you only ever shoot with a pinhole camera, your most important tools in photography are lenses. If you take photography seriously enough to try to pass a professional certification in it, you should really understand your most important tools. I would expect any self-respecting photographer, "professional" or "amateur" (including those who care enough about it that they spend time on photography forums like this one!), to comprehend how a lens projects an image, and to be able to correctly visualise what will happen without even setting up the test.</p>

<p>If people can go one step further and understand the formula; even better. The formula dates from at least the early 17th Century, so it's not exactly rocket science. They were still burning witches at the stake back then.</p>

<p>Of course there are many different genres of photography, and knowing or not knowing such things may not make a difference to your results. But would you not feel more complete by knowing, and more prepared for the unexpected? To be a surgeon, it is not enough to merely be an excellent seamstress - with a superb technical skill at cutting and sewing up body parts. A deeper knowledge of the pathology and physiology of the body is also required, among much else.</p>

 

[ondebanks]

<blockquote>

<p>Also, if you use "Test Taking 101" techniques for elimination of distracting answers, "C" was the only definitive answer. Both "B" and "D" are saying the same thing, so they can easily be discounted, and "A" could be easily construed as ambiguous <em>(Which </em>image is larger?). Which leaves us with "C".</p>

</blockquote>

<p>Well spotted, Larry! But I would hope that all the other questions in the test are less soluble by such reasoning!</p>

 

[ondebanks]

<p>Adrian,</p>

<blockquote>

<p>So "S" cannot change, but it will if you plonk a digital back on the camera, could be anything from a few megapixels to a lot of megapixels.</p>

</blockquote>

<p>No. Forget about the format, the sensor, the megapixels. "S" is measured in units of millimeters, or microns if you prefer more precision. If the lens makes an image of a person's head 10mm wide on a piece of film, it will be 10mm wide on a digital sensor as well. That's all there is to it.</p>

[ondebanks]

<p>Iverson said:</p>

<blockquote>

<p>Everything else being equal, the image in the 35mm viewfinder will be larger than the image in the MF viewfinder.</p>

</blockquote>

<p>Leigh said:</p>

<blockquote>

<p>The viewfinder image is totally irrelevant to the question, which is about the photographic image, i.e. the image on the film or sensor.<br>

You can make the viewfinder image any size you wish. It's a separate optical system.</p>

</blockquote>

<p>Leigh is right. And furthermore: the image sizes in the viewfinders will <em>also </em>be identical, if you remove the viewfinder optics and view the focusing screens directly, in their naked glory! The ground glass is after all a proxy for the film/sensor plane.</p>

[mjferron]

<p>Its's why I refuse to be a professional photographer. Don't want to spend my time answering questions like that. We all know if you put a 300 on say a aps camera you will get an image that frames pretty much the same as if you put a 450 (?) on a full frame standing in the same spot. Cropped not magnified but hey it works.</p>

<p>To further complicate matters since 35 is the standard folks use to cross reference focal legnths among different formats tell me how it works since 35mm is a more elongated image compared to say 6x7? So a 50 on 6x7 is a wide angle and roughly equates to 25mm on 35 but is that in height or width? To me it can't be both.</p>

[bob_sunley]

<p>Michael wrote: "To further complicate matters since 35 is the standard folks use to cross reference focal legnths among different formats"</p>

<p>Since when? It wasn't a comparison standard 50 years ago, and really isn't today, except as a mass market marketing thing for small sensor "35mm cameras". A "normal" lens has always had a focal length approximately equal to the diagonal in the image frame, no matter what the format, unless is is a panorama style like 6x17.</p>

<p> </p>

[bill_pearce2]

<p>I find the question a little confusing, but I suck at math, although it didn't stop me from making a living as a professional photographer for most of my life. What I want to know is who is giving this exam, and what would someone's motivation be for getting this?</p>

<p>There are lots of folks in the business of giving out some sort of credentials for folks who seem to need them. Look at the weathermen on your local station, they all have some sort of certificate from some outfit in it for the money, and still you don't know what the weather will be.</p>

<p>I remember a time when I was working as a photographer for an airplane factory, and the chief photog was big on the PPA. I looked into the group and its classes, and discovered that since we didn't do weddings at the factory, and I didn't shoot any protraits, it was a waste of my time. They did print snappy ceritficates, though.</p>

[steve m smith]

<p>Who is doing the certifying here and what makes them qualified to do it?</p>

[greg_kowalczewski]

<p>Provided that when the 300 mm lens is attached to both cameras the lens to focal plane distance remains the same (which is what I think the question wants you to assume) then the image size created will be the same (sort of like looking through a magnifying glass - anything in front of it the <em><strong>same distance away</strong></em> will be magnified by the <em><strong>same amount</strong></em>). So "C".</p>

[danielsimionescu]

<p>If the question is not about film, it's common sens (for me, at least) to define image size by the number of pixels (check what Photoshop says when you check Image Size :).<br>

Considering the pixel density (good point, Frank) the result can vary in either way, which leads me to the conclusion of a bad wording (too bad for a "Certified Professional Photographer Exam" IMO).</p>

[graham_martin2]

<p>To those who are wondering what other topics are contained in the Certified Professional Photographer exam, they are as follows:</p>

 

<ul >

<li>Camera, lenses, and attachments (15%) – selecting the appropriate lens based on subject size, distance, and desired perspective.</li>

<li>Composition and design (17%) – subject placement within image, props, location, posing, color harmony, coordination of subject and background.</li>

<li>Digital post production (13%) – color space, file formats, resolution, calibration, manipulation of digital images in Photoshop.</li>

<li>Exposure and meters (20%) – how to meter for correct exposure, the relationship between shutter speed, ISO, and aperture, and how to verify proper exposure (histograms).</li>

<li>Film, digital capture and output (15%) – selection of appropriate film based on lighting conditions and final product needed, identify and correct problems in both negative printing and digital image printing.</li>

<li>Lighting (20%) – to how best light a subject, types of lighting, lighting equipment, lighting ratios, lighting usage (main vs. fill), selection of appropriate filter to color correct a light source, inverse square law.</li>

</ul>