dfrost01 Loc: Princeton, NJ

I know a teleconverter reduces the amount of light reaching the sensor, but does it also reduce the resolution of the image? I will be shooting the solar eclipse this August with my Sony a7r2 42MP camera. Planning to use the Sony 70-400 full frame lens. If I use the camera in crop mode to increase my focal length, it will reduce the resolution to about 20MP. Need to decide which way to go. Crop mode or full frame with teleconverter?

letmedance Loc: Walnut, Ca.

Shooting in crop mode will do just that, crop your picture in camera, it will not increase your magnification, the teleconverter will.

oldtigger Loc: Roanoke Virginia-USA

Crop mode does not increase your focal length.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Crop mode is the same as cropping in post.

In the simplest terms a teleconverter changes the focal length. A 1.4X will diminish the maximum opening by 1 stop, and you will lose about 5% of your image quality. If you stop the lens down one stop, it will be fine as long as the optic is extremely sharp to begin with. If the lens has flaws or is weak at 400mm, it may not be much better than just cropping.

OviedoPhotos

I use a TC 1.4x on a prime lens and notice a degradation of picture quality but its slight. Given the choice here, IMO, your probably better off cropping.

par4fore Loc: Bay Shore N.Y.

Use the TC1.4, you can still crop in post if you want. I would never tie my hands by cropping in camera, it buys you nothing. Good luck.

dfrost01 Loc: Princeton, NJ

Thanks,everyone, for clarifying

jerryc41 Loc: Catskill Mts of NY

Some solar tips -

http://www.mreclipse.com/SEphoto/SEphoto.html
http://www.eclipse2017.org/2017/photographing.HTM
http://www.nikonusa.com/en/learn-and-explore/article/h20zakgu/how-to-photograph-a-solar-eclipse.html
https://photographylife.com/how-to-photograph-a-solar-eclipse

Steve Perry Loc: Sylvania, Ohio

I wrote an article on this exact topic last year:

http://backcountrygallery.com/use-teleconverter-crop-image/

Architect1776 Loc: In my mind

I do not know of the quality of the Sony TCs. But the Canon MIII series with the lenses matched to them beat cropping the photo every time. But if there is no matched TC for your lens with MTF the same as without then it is matched to your lens and will work just fine.

jackpi Loc: Southwest Ohio

Is the Sony 1.4TC compatible with the 20-400mm lens? Teleconverters work best on prime lenses. If you haven't bought the 70-400mm lens yet, you might want to consider renting a Sigma 150-600mm Sport lens with the Canon mount and the Sigma Canon-Sony adapter.

Fotoartist Loc: Detroit, Michigan

What filter are you using for the eclipse?

amfoto1 Loc: San Jose, Calif. USA

First, be aware that cropping in-camera is no different than doing the same crop later in your computer. It doesn't matter whether you set the camera to APS-C crop or if you shoot full frame and later crop the image to the same dimensions in post-processing... the resulting cropped image is exactly the same, either way. So, why bother doing the in-camera crop?

On the other hand, a teleconverter will increase the magnification of your lens. The problem is, there are almost infinite possible combinations of teleconverters and lenses. There is always some loss of image quality to any teleconverter... but it's very difficult to predict how much unless you can find someone using a specific teleconverter with exactly the same lens.

In general terms... a 1.4X teleconverter "costs" less light loss (one stop) and it's weaker magnification makes for less loss of image quality than a 2X teleconverter (two stops of light loss).

But there are still a lot of different TCs. Just for example, Kenko currently offers three 1.4X: Pro 300, MC-4 and HD.

As far as I know, the Kenko HD is relatively new and only offered in Canon mount (to accommodate EF and EF-S lenses). While it's often more expensive than the other two, it uses fewer elements which usually indicates lower quality.

The Kenko 1.4X Pro 300 model is considered pretty darned good and sharp across the entire image area and might be a better choice for full frame cameras. It is more expensive and uses 5 elements in 4 groups.

The Kenko 1.4X MC-4 is a lower priced model, quite sharp in the center of the image, but less so in corners and at the edges... so it might be a better choice for APS-C cameras. It uses 4 elements in 4 groups.

You'll find similar variation in teleconverters from Sigma and Tamron (AFAIK, Tokina doesn't offer any TCs... probably because Tokina and Kenko are subsidiaries of the same parent company). I have no experience with any TCs that Sony themselves might offer... OEM products might be better matched with the company's lenses, but tend to be more expensive (that's certainly the case with the Canon lenses and TCs I use).

You need to very carefully investigate photographing a solar eclipse... Done incorrectly you can damage your camera or even do permanent injury to your eye! A special Solar Filter is absolutely mandatory.

Bobspez Loc: Southern NJ, USA

I looked at your article and video. The one question you posed that I didn't hear an answer to was how does an FX image with a TC compare to an FX image without a TC, cropped in Photoshop?

Steve Perry Loc: Sylvania, Ohio

The crop would be the same regardless of whether it happened in camera or in Photoshop, so the results would also be the same as described in the article.