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Observations on using stacked TCs to get to 400mm
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<blockquote data-quote="gustafson" data-source="post: 562870" data-attributes="member: 40735"><p>I've been looking at ways to get to a 400mm focal length affordably and with decent IQ. While saving up for a big boy telephoto, I happened to realize that I had 2 TC-16As (one modified to work and autofocus on my D7100, and one unmodified) that could be stacked to get me that additional reach. My longest primes are currently a manual AI'd 200 f/4 QC and a factory AI'd 180 f/2.8 PC, so it wasn't long before they went on my stacked TCs to see if it would work at all. Below are my observations and a link to sample images. Would appreciate if others could look at the samples and share any other observations, or any thoughts on how the results could be improved.</p><p></p><p></p><ul> <li data-xf-list-type="ul">Link to sample images (all SOOC jpegs, handheld with AI'd 180 f/2.8 PC and two stacked TC-16As, except where noted): <a href="https://www.flickr.com/gp/89411942@N04/y8998Y" target="_blank">https://www.flickr.com/gp/89411942@N04/y8998Y</a></li> <li data-xf-list-type="ul">Using the 200 f/4 QC on the stacked TCs resulted in too much AF hunting indoors, even wide open, and what photos I got didn't look great, so I didn't bother testing it further.</li> <li data-xf-list-type="ul">The 180 f/2.8 PC, on the other hand, seemed to work pretty admirably (with certain limitations) with the stacked TCs. I was able to get decent shots at lower ISOs and shutter speeds than I would have expected with 2TCs and the long focal length (460mm f/7). All of the test shots linked above, and observations below, are with this lens and stacked TCs.<ul> <li data-xf-list-type="ul">Given I was stacking TCs, I expected images to be horrendous. However, I was surprised to get surprisingly detailed shots for subjects within 25 feet. Given the light loss due to the TCs, use of a flash helped considerably, although it often introduced CA in the catchlights. Use bounce flash if possible for reflective objects.</li> <li data-xf-list-type="ul">Shots at wide apertures near the min focusing distance were often soft, but I expect that is due to the thin DOF at those distances which makes focus vulnerable to slight movements of the camera to or away from the subject.</li> <li data-xf-list-type="ul">Beyond 75 feet to infinity, the detail was not great, as you can see from the moon shots or the BIF shot. To begin with, if the second TC-16A (the one that sits on top of the TC-16A that is attached to the camera) does not have its element extended all the way out, the setup doesn't even focus at infinity. Once I ensured that, I was able to focus at infinity, but the shots were terrible as you can see. Any tips to fix that will be appreciated. If it is even possible, I will be blown away, as it will give me the option to use this rig for BIF and distant birds, although I suspect a single TC with cropping might give superior results.</li> </ul></li> </ul><p></p><p>Look forward to your comments and reactions.</p></blockquote><p></p>
[QUOTE="gustafson, post: 562870, member: 40735"] I've been looking at ways to get to a 400mm focal length affordably and with decent IQ. While saving up for a big boy telephoto, I happened to realize that I had 2 TC-16As (one modified to work and autofocus on my D7100, and one unmodified) that could be stacked to get me that additional reach. My longest primes are currently a manual AI'd 200 f/4 QC and a factory AI'd 180 f/2.8 PC, so it wasn't long before they went on my stacked TCs to see if it would work at all. Below are my observations and a link to sample images. Would appreciate if others could look at the samples and share any other observations, or any thoughts on how the results could be improved. [LIST] [*]Link to sample images (all SOOC jpegs, handheld with AI'd 180 f/2.8 PC and two stacked TC-16As, except where noted): [url]https://www.flickr.com/gp/89411942@N04/y8998Y[/url] [*]Using the 200 f/4 QC on the stacked TCs resulted in too much AF hunting indoors, even wide open, and what photos I got didn't look great, so I didn't bother testing it further. [*]The 180 f/2.8 PC, on the other hand, seemed to work pretty admirably (with certain limitations) with the stacked TCs. I was able to get decent shots at lower ISOs and shutter speeds than I would have expected with 2TCs and the long focal length (460mm f/7). All of the test shots linked above, and observations below, are with this lens and stacked TCs. [LIST] [*]Given I was stacking TCs, I expected images to be horrendous. However, I was surprised to get surprisingly detailed shots for subjects within 25 feet. Given the light loss due to the TCs, use of a flash helped considerably, although it often introduced CA in the catchlights. Use bounce flash if possible for reflective objects. [*]Shots at wide apertures near the min focusing distance were often soft, but I expect that is due to the thin DOF at those distances which makes focus vulnerable to slight movements of the camera to or away from the subject. [*]Beyond 75 feet to infinity, the detail was not great, as you can see from the moon shots or the BIF shot. To begin with, if the second TC-16A (the one that sits on top of the TC-16A that is attached to the camera) does not have its element extended all the way out, the setup doesn't even focus at infinity. Once I ensured that, I was able to focus at infinity, but the shots were terrible as you can see. Any tips to fix that will be appreciated. If it is even possible, I will be blown away, as it will give me the option to use this rig for BIF and distant birds, although I suspect a single TC with cropping might give superior results. [/LIST] [/LIST] Look forward to your comments and reactions. [/QUOTE]
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Observations on using stacked TCs to get to 400mm
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