If the longest telephoto lens you own never seems to get you in tight enough to your subject, you have three choices. The first is to get up and get physically closer to your subject. If you can’t, for whatever reason, do this, you can either take the picture as is and crop it to your liking post-capture, or you can use a teleconverter.
Photographs © Allan Weitz 2021
Either method will work, albeit at a cost. As for the price of cropping versus the price of using a teleconverter? That depends.
What Are Teleconverters?
Teleconverters are lens accessories that magnify the central portion of the image field of your lens, enabling you to fill the frame at up to twice the magnification of a compatible telephoto lens. Also known as extenders, or in the case of 2x teleconverters, “doublers,” teleconverters mount between your camera and lens and are available from OEM or third-party manufacturers. Depending on the make and model, teleconverters increase the magnification of your lens by a factor of 1.4x, 1.7x, or 2x.
In the case of a 70-200mm lens, a 1.4x teleconverter converts the lens to a 98-280mm equivalent zoom, while a 2x teleconverter converts the same lens to a 140-400mm equivalent zoom. Most teleconverters are about the same size and weight as a 50mm normal lens, which makes them far more practical to tote about than your average 500, 600, or 800mm long-range lens.
And the Cost for Such a Convenient Lens Accessory?
There is, unfortunately, a price to be paid for such a handy device and, in the case of teleconverters, the costs include a loss of light transmission and resolving power.
Any time you integrate additional lens elements―including filters―into the light path of an existing camera and lens system, it has an impact on image quality. It’s not that the image files are no longer sharp; they are, but any time you add additional lens elements into an otherwise optimized light path, you invariably lose image detail.
In the case of zoom lenses, the levels of image-quality loss often vary as you zoom through the lens’s focal range.
How Much Light Do You Lose When Using Teleconverters?
Calculating the degree of light loss is the easy part of the equation; you lose 1 stop of light with a 1.4x teleconverter, 1.5 stops with a 1.7x teleconverter, and 2 stops of light when using a 2x converter.
When shooting in low light, this can be an issue, especially when using lenses with small maximum apertures. As an example, a 70-200mm f/2.8 lens with a 2x teleconverter effectively becomes the equivalent of a 140-400mm f/5.6 lens, and that’s before you stop the lens down. In the case of a 3x teleconverter, your maximum aperture of 5.6 now effectively becomes f/16.
The problem is many autofocus systems begin losing speed and accuracy once the maximum aperture of the lens becomes less than f/5.6 - f/8, and this is before you stop the lens down for better image quality and additional depth of field. On bright, sunny days, this is pushing the limits of many AF systems, but once the clouds roll in or you move indoors, you’re skunked.
Your camera’s in-camera exposure system compensates for any exposure loss. If you are setting your exposures manually, you must factor in this light loss when calculating your final exposure.
Can Teleconverters Be Used with Any Lens?
Unfortunately, the answer is no. Teleconverters are designed for a limited number of telephoto and telephoto zoom lenses and are totally incompatible with wide-angle lenses.
Are Some Cameras Better than Others When It Comes to Teleconverters?
In effect, yes. Teleconverters date back to the days of 35mm and select medium format film cameras. The advantage of using teleconverters with film cameras is that, with the exception of some of the slower, finer-grain film emulsions (ISO 25 – ISO 125), the grain that was inherent to most film stocks typically masked any perceptual loss of resolution due to the use of a teleconverter. The loss was there, but it was camouflaged by the grain of the emulsion. So yes, when used with film cameras, a teleconverter can be preferable or, at the very least, equal to cropping in terms of the degree of image degradation one would notice.
In the case of digital cameras, if you use a teleconverter with a low-resolution (12MP-18MP) mirrorless camera or DSLR, you may not notice the loss of image detail compared to using the same lens and teleconverter on a high-resolution (36MP-60MP) mirrorless camera or DSLR.
Similarly, if you plan on cranking the ISO sensitivity of your camera anywhere north of 25,000, the loss will be there, but just as film grain masks any loss of image quality, you’re most likely not going to be able to see it.
Camera and Lens Mount Alignment
One last thing about teleconverters: Regardless of how sharp a lens might be, if the parallel alignment of the camera mount and lens mount isn’t 100%, the image isn’t going to be 100% sharp. When using a teleconverter, you are adding a second alignment point into the mix—this time between the camera, the teleconverter, and the lens. If any of these contact points aren’t aligned perfectly, then, depending on the variance, you are going to lose a measure of sharpness somewhere within if not across the image field. If the surfaces of the camera and lens mounts aren’t perfectly parallel to one another, all bets are off once you start eyeballing the image files at 100% magnification on your computer screen.
Alignment issues are less likely when using OEM teleconverters compared to converters from third-party manufacturers, which, depending on the manufacturer’s tooling, may not be machined as critically as OEM products.
The Pluses and Minuses of Post-Capture Cropping
Cropping a photograph post-capture is a surefire way to frame the image the way you saw it in your mind’s eye on occasions where it wasn’t possible to step up closer to fill the frame to your liking. As with teleconverters, cropping comes at a cost.
There’s No Free Lunch
In the case of cropping, the price is a slight decrease in resolution as the image is magnified, along with an equal increase in any noise—or in the case of film, increased grain.
Just as eyeballing your image files at 100% on a large monitor reveals minute particles of dust and lens aberrations you’d never notice on the camera’s LCD or on a small print, when you crop an image, you correspondingly magnify any dust and/or defects in the file or negative. In the case of film negatives, you correspondingly increase the size of the grain, which, depending on the final print size and intended viewing distance, may or may not be an issue.
Cropping Is Not Limited by Lens Choice
Teleconverters are only available in fixed magnifications (1.4x, 1.7x, and 2x) and are only compatible with a limited number of telephoto and long focal length zoom lenses. Conversely, any photograph can be cropped in an infinite magnification range regardless of the focal length of the lens used to capture the photograph. That’s a plus in favor of cropping.
Is Cropping a Photograph Ethical?
Crop is not a Four-Letter Word. If cropping photographs results in photographs with greater graphic and/or emotional impact, why is cropping considered an act of blasphemy by so many otherwise open-minded photographers? When you aim your camera a little to the left or right before pressing the shutter button, are you not in a sense cropping the image in-camera?
Then there’s the question of sensor size and equivalent focal length. When you mount a 100mm lens on an APS-C camera to capture the angle of view equivalent to a 150mm lens, or equivalent to a 200mm lens when mounted on a Micro Four Thirds camera, are you not in fact cropping the final image? The act itself occurs passively and out of public view, but for all intents and purposes, it’s cropping.
The following sample images were captured using a Sony a7R IIIA, a Sony FE 200-600mm f/5.6-6.3 G OSS zoom lens, and Sony FE 1.4x and FE 2x teleconverters. It should be noted there are comparable camera/lens/teleconverter systems available from all of the major OEM camera and lens companies, as well as third-party manufacturers.
It should also be noted there can be noticeable variances in performance between products from OEM and third-party manufacturers alike, including the ones we all know and love. However, the following sample images illustrate the differences between photographs taken using teleconverters and photographs cropped to the same image size as those captured using a teleconverter. As always, your test results might vary from my test results simply because every lens and teleconverter has its own set of characteristics and degrees of variance.
In the photos above, the cropped 200mm image (left) retains better detail than the same composition captured at 200mm with a 2x teleconverter (right).
Both of the above images emulate the field of view of a 400mm lens. The cropped version (left) has an edge in terms of clarity compared to the photograph taken at 200mm with a 2x teleconverter (right).
One Last Thought
As explained above, there’s no such thing as a free lunch, but cropping photographs doesn’t cost a dime, and there aren’t too many things in life that are truly free these days. Teleconverters cost a few hundred dollars. Weigh the benefits and see what works best for your particular needs.
Do you have thoughts on this topic, or have you compared teleconverters with comparably cropped images? If so, let us know about your experiences in the Comments section, below.
Interesting and timely article as I am heading back to Yellowstone in June and look forward to giving my new Nikon 500mm lens a workout along with my D850 (both from B&H of course). When in Yellowstone two years ago, I had several opportunities to take wildlife pictures at the crack of dawn. At that time, my longest reach was an 80-400 lens that I combined with a 1.4 teleconverter to attain a 560mm equivalent. The teleconverter cost me a very valuable stop of light (or more?), which meant a higher ISO and exposure times than I would have liked. While the pictures were good, they were nowhere near sharp (yes, I was using a tripod). My question is whether in these low light situations using the 1.4 TC and sacrificing a very valuable stop of light makes sense or should I not use the teleconverter and simply rely on cropping in post (given the presumption that I can hopefully get a sharper picture without the TC). As my D850 has upwards of 45mp it would seem I that I would have some pixels to spare if I took the "crop in post" (I would not be looking to produce any large prints, etc. from the shot)? Welcome any and all thoughts.
Thanks for shopping at B&H!
Great question and your teleconverter experience seems to echo my own there.
Personally, I might ditch the TC and just crop in post—or shoot with it on and off to see if you get a sharp (enough) shot with it on. With the converter, if possible, keep at mid-range apertures like f/5.6 or f/8 to try to maximize sharpness.
My last $0.02 thought is to print out your teleconverter shot(s) to see if the lack of sharpness on the screen is translating to the print. That might help you decide. Many of us, me included, spend time in Lightroom or Photoshop zooming in past 100% to verify sharpness, and being disappointed when it isn't there—forgetting that you'd never see that (perceived) softness in a 4x6, 5x7, or even 8x10 print.
Thank you for reading! Let us know if you have any follow-ups!
Thx for the follow-up Todd. As you can appreciate, when shooting wildlife (especially in Yellowstone when encountering “must get” shots) you typically don’t have the time to try a shot with and without the TC (those bears don’t typically like to pose for you :)) When combined with the fact that when using a TC it sometimes randomly takes extra time as it searches for focus, I think going without the TC and simply cropping more makes sense. That being said, not a bad idea to print it out as I am guilty of magnifying the photo in LR by 100% (or more!) and likely having unrealistic expectations.
I think the plan should be to keep the TC in the bag and get the shot unless the bear decides to hold a pose long enough for you to attach the TC and try to get the more telephoto shot!
Good luck and happy shooting! Let us know if you have more questions!
Thanks for the explanation on cropping vs TC. So maybe this question is a little off topic, but how does using a TC compare to switching to DX mode? I have a Nikon Z6 and I can switch from full frame, FX mode, to DX or crop mode which I believe is like changing to an APS-C camera. I don't have a TC so I haven't done a comparison on my own. Any thoughts on using DX mode, on a full frame camera, as apposed to using a TC?
Not too off topic!
When you switch from FX to DX mode on a Nikon full-frame digital camera you are basically cropping the image inside the camera. You can get identical results by cropping the image with post-processing software. The purpose of the DX mode is to allow you to use DX-specific lenses on your full-frame camera and avoid the vignetting that would be created by the DX lens's smaller image circle not filling a full-frame sensor.
As the camera is just cropping the image, you aren't really gaining a telephoto advantage per say. But, if there was an advantage to DX mode/cropping, it would be that 1) you would be avoiding potential optical issues caused by an optical teleconverter, and 2) you would not experience any light loss as you would with an optical teleconverter.
And, as DX mode with a non-DX lens is the same as cropping, I wouldn't be inclined to use it while shooting—saving the cropping for processing later.
Thanks for your question. Please let me know if you have follow-ups! Thanks for reading!
In these examples, the high-resolution Sony and lens combination without its teleconverter and post-processing a significant crop clearly wins. So, should only Sony owners take heed and not invest in its teleconverter? Maybe not because the article does infer that this is true throughout the camera and lens brands but does not offer comparisons to results using similar Canon or Nikon equipment to confirm the insight offered in the article. It would have been a nice edition.
Thanks for your observation and comments.
In my experience, I have not fallen in love with the Nikon teleconverters that I tried. I know there are many photographers that get exceptional results using teleconverters, but I, unfortunately, was not one of them. When adding more elements of glass between the subject and the sensor, you often run the risk of degrading the image a bit. Having said that, some teleconverters seem to work better than others—either manufacturing variations or, maybe photographers with better skills than mine!
If you are in the market, you can always take a teleconverter out for a spin and see if you get great results. If not, B&H does have a generous return policy.
Please let us know if you have more questions and thanks for reading!
One downside of cropping is that you may not have enough pixels left for the print size and resolution you want to make. I've experienced this with my Fuji APS-C sensor camera. When shooting a square format, you already lose 1/3 of the available pixels from the sensor. Cropping further reduces the final image pixel dimensions,
You are correct but print size/resolution also can depend on viewing distance and how you are printing/displaying. You can run out of pixels, but, in general, digital photographers these days have excess (?) pixels to play with—unless you are making huge prints!
I used to make nice 13x19 prints from uncropped sub-6MP cameras in the past…that would be a pretty severe crop on today’s 24MP+ sensors!
Thanks for reading!
I downloaded the images of the Heublein Tower.
The JPEG artifacts of the image with the TC seem significantly worse. ??
I doubt that the images displayed here are well suited for "pixel peeping".
I do believe that our background system sends images “through the wash” before posting here as I sometimes see that they look different on our page than they looked on my screen. As far as a technical explanation, I cannot give you one, unfortunately.
Having said that, the light-reduction caused by the teleconverter will change the image’s signal-to-noise ratio and that may affect how JPEGs are crunched due to changes in digital noise levels/structures.
Thanks for reading!
Nothing that a $7,000-$15,000 lens won't solve.
Maybe, but for about $500 I can put a converter in my bag or pocket "just in case" and use it if I need it. A 600/4 is great; it's faster and it's sharper than my 200-500, and takes converters better than most zooms, however it needs a heavier tripod, a gimbal head and a sherpa: it stayed home. I took the 2-5 and only used a 1.4x converter once for a wolf shot at about 250 meters at 500 mm and on a crop sensor: it was that or nothing. Image was "better than no picture" and I was OK with that, but I still cropped some for the final print. 600 would likely have been better option.
My general observation is that (in my case, anyway) technique with long lenses (with or without converters) has at least as much impact on the final result as the quality of the lens, whether it is a zoom or prime, uses VR / IS, etc. I think there can be a temptation to fault (extenders, or zoom lenses, or whatever) optics rather than suck it up and admit that operator error was the primary cause of un-sharpness, etc. I am not pointing fingers at anyone, just admitting my own foibles.
Thanks to Allan Weitz for the article and for your comment.
Trip mentioned above was for Coastal Brown Bears in Katmai NP and involved float planes and skiffs (about 20' long boat) to get to beach from larger boat "anchored out".
Loved this, Guy. Your second paragraph was spot on. We blame everything but our technique for our photos that don't pass muster. I also enjoy anything in which Allen appears or that he writes.
I am always quick to blame my gear for the bad photos and praise my mad skills for the (few) good ones I take. 😊
Thanks for reading and thanks for being a fan of Allan’s stuff! Be sure to tune into the B&H Photo Podcast to get an earful (literally) of Allan! 😊
Well said here, too! Teleconverters certainly have their place in the photographic ecosystem—if they didn’t, they wouldn’t exist. And, sometimes they are the best/only option, as you found on your trip to Katmai.
Thanks for reading and thanks for your comments!
Well said! I know a place where you can buy those $7000-$15,000 lenses! 😊
Thanks for reading!
In looking at these 3 images I personally like the cropped signs and bench just a little more than the images with the converter. The differences are very, very small. The cropped images are just a tiny, tiny bit sharper and the they have just a tad more contrast. The tower image to me is clearly better with the TC because the roof tiles are distinctly better defined with the TC than the enlarged image.
That said, I think people should always consider Post Production when making such decisions and before spending hundreds of dollars or even thousands more on a better lens or camera. Not only can post processing wipe out these these tiny or small differences, they will improve the image in other and more significant ways. I have never worked with a digital image however perfect it was out of the camera, that wasn't made just a little sharper, and/or with slightly more pleasing contrast and/or with slightly better color balance and/or slightly saturation following a few mintues with it in Post.
Though Photoshop remains at the core of my workflow, now there are many alternatives. Some are as robust as PS but most aren't. Instead they can all adjust the basics, are much easier to use and cost a lot less. Some excellent ones are free. If you are willing to spend a few minutes doing post, the very small differences on the sign and bench would more or less completely disappear. I am less sure about the roof tiles but there is no doubt in my mind the enlarged tower image would be much better than it is now and that the differences btw the enlarged image and the TC image would become tiny.
Post process will always produce a little better image in some way. It takes only a few minutes These take only a few minutes to change and the changes can be applied to many similar images at once.
The real danger is once you learn how much control you have is that you may get sucked in and start on working on small areas of a single image, say to reduce a highlight or shadow on a face, or to bring out more detail in the clouds, or the shadow under a tree.I've spent many, many hours perfecting a single image. To me it's worth it and I have the time to do it but certainly this isn't for everyone.
If you not doing any post you are missing out on some of the finest tools that in my mind are in some ways as important as the camera and they cost a lot less.
I won’t argue with you on any of your points. Even a little bit if post-processing can go a long way to improving an image. I am a Lightroom user and show my students how 30-seconds of slider adjustments can make a huge difference in the appearance of an image.
And, yes, with time, patience, energy, and skills, you can spend hours perfecting a single image—something I have never tried, as I lack the skills! 😊
Thanks for sharing your thoughts and thanks for reading Explora!
With the software updates to Lightroom, Photoshop, and now Topaz Gigapixel, how does enlarging a photo to 2x its normal resolution fit into this topic? For example, if I convert a 45mp image to 90mp, will the resulting crop be sharper than cropping the original, unenhanced image?
The use of a lens with a teleconverter attached to it would yield sharper results as opposed to cropping and interpolating the image.
So is it safe to say as a rule of thumb , that for high megapixel cameras it is better to crop, but with low resolution cameras it is better to use a teleconverter? What about for video?
While I wouldn't quite state that is a rule of thumb, I guess yes, you may consider that statement a truism or adage (of sorts). You will have some loss of image quality with either cropping or the use of a teleconverter. However, with lower-megapixel cameras, resolution loss would be less noticeable when using a teleconverter. The issue with cropping is you are literally throwing away the unused pixels, thus, you are losing resolution. This is less of an issue if the image is to be used online as its final product, or if you have a high-megapixel count camera and can safely lose some resolution, but if you plan to print a large print and you crop tight on a low-megapixel count camera, you may lose the quality needed for a photo-quality print, and/or you may have to interpolate the image file or use software to attempt to regain details from the cropped image.
One other point to consider is dust on the sensor. Cropping does not require opening the camera/lens interface and exposing the sensor to the environment, but adding/removing a teleconverter does. That often adds fuzzy splotches to the images for almost all lenses (a few come with built-in teleconverters). Unlike film, where the "sensor" is changed with every shot, those hard-to-see-on-a-viewfinder spots persist through the rest of your shoot; it's why I gave up on extension tubes for macro and bought a longer focal length macro lens instead.
In the same vein, the "breathing" of some zooms draws in dust as their internal volume changes. Prime lenses (and one extra camera body to keep some versatility without changing lenses) avoid the problem.
Dust on the sensor, as opposed to film, is a recurring problem, yes. Thanks for posting your workarounds here, Matthew B. We hope that they may come in handy for some of the other macro fans who read Explora.
Thank you, that's a very interesting experiment to make! Like with depth of field, it seems that high-megapixel cameras are just a bit different. Could you please correct the statements about light loss in the "How Much Light Do You Lose When Using Teleconverters?" section? Take a look at another B+H article, https://www.bhphotovideo.com/explora/photography/hands-on-review/things…, that I think has the correct numbers (1, 1.5 and 2 stops, respectively).
Thanks for sharing your eagle eye. We have made the edit and hope that you continue to enjoy our articles! We appreciate your comments.