Thanks for all the feed back. It is amazing all the different ways to look at this problem. imagemeister says it clearly, 400mm vs. a 300mm is NOT a significant increase. Go to 500/600mm to be worth your while $$$. I was hoping for something light and compact, but that doesn't seem in the cards.

Thanks all for the input. The "Nikkor lens simulator" was a big help as I got to see the differences first hand and I especially want to thank craggycrossers. For every doubling of the length in mm, the image size doubles. I have a Nikkor 55-300mm now and I am thinking about the new Sigma 100-400mm. I am using a Nikon d5300 which is a crop sensor. I am aware that the Nikkor is not in the same category as the Sigma as to sharpness. I have been photographing a bald eagle from about 300 yards and the image is quite small. At the most, I can blow it up by 50%. I am using a Vanguard tripod which is a monster. I'm not sure that the Sigma will be adequate. Maybe I should use something longer, like 500mm or 600mm. Any advice?

I am considering buying a 400mm telephoto and I have a 300mm telephoto now. What can I expect by going to the longer telephoto. Will the image be 50% larger or 100% or something else? From some rudiment experiments I have done it appears that the image doubles when the telephoto doubles as going from 200mm to 400mm but not exactly. Any ideas?

I bought a Lumix FZ1000 used from B&H. I try to get used cameras that are rated 9 or above. It is a wonderful camera. The view finder is bright and very clear and 100%. It has an excellent Leica lens. I can't say enough good about the lens. It is a f/2.8 mm to f/4.0mm maximum and goes out to f/8.0. It zooms from 25-400mm. Like the Sony on some of its lenses, there is an extension for 400 - 800mm which is also excellent. It takes screw on filters which most of the Lumix lenses do not do. The lens is built in so no bulky bag of lenses are needed. It is light but also as bulky as most DSLR's are. That is the only problem I see. I would have to rate it with the best Nikon or Canon. Very sharp, good contrast, good stabilizer reasonable price.

I am using on my Sony a6000 a Samyang 12mm f/2 for APS-C or f/2.8 for Full Frame. It is a manual lens but don't let that put you off. Because it is so wide, it is easy to set to f/5.6 and Aperture and get excellent photos from 2 feet to infinity. I set the distance to between 1 meter (3 feet) and in infinity, and the photos are very sharp. According to ephotozine.com, from f/2 to f/8 the lens is Excellent of better. From f/2.8 to f/5.6 are off the scale. The price is $319 to $399 at B&H photos depending on Camera.
I also have the Sony 10-18mm, f/4 which is excellent but costs a lot more. For a Nikon/Canon, the Sigma 8-16mm is excellent or the Sigma 10-20mm.

A few months ago I bought a refurbished Lumix ZS50 from B&H for $200 less than a new one. I am very happy with the camera. I think what is more important than the "refurbished" name is that it is bought from a reliable vendor with a good warranty. This blog is a good source for reliable vendors and those to avoid.

I recently bought a used Nikon D5300. I read the reviews of the D5500 and D5600 and altho they have upgrades, none interested me. I had a D5300 previously and was very pleased with it. New doesn't necessarily mean better. The D5300 cost me about half of the new model and it is in excellent condition.

I am considering a Sigma 150-600mm f/5-6.3 Contemporary. It is very reasonable, below $1K and has excellent ratings on B&H and Flickr.

I am considering a Sigma 150-600mm f/5-6.3 Contemporary. It is very reasonable, below $1K and has excellent ratings on B&H and Flickr.

I have used Corel since they purchased PaintShopPro many years ago. I also used Adobe Elements. I found that Corel was more intuitive and easier to learn. The latest Elements has you jumping around to do the simplest things. I am sold on Corel. You might get both for free for a trial and then decide which you like the best.

I have used Corel since they purchased PaintShopPro many years ago. I also used Adobe Elements. I found that Corel was more intuitive and easier to learn. The latest Elements has you jumping around to do the simplest things. I am sold on Corel. You might get both for free for a trial and then decide which you like the best.

I have used Corel since they purchased PaintShopPro many years ago. I also used Adobe Elements. I found that Corel was more intuitive and easier to learn. The latest Elements has you jumping around to do the simplest things. I am sold on Corel. You might get both for free for a trial and then decide which you like the best.

I'm 72 but not too old to be corrected. I'm with the Japanese. Although, I have sold all my Nikon gear to my brother-in-law and bought a Sony a6000 which I am very happy with. I find that the Nikon lenses in general are superior to the Sony. The Samyang/Rokinon are much sharper but manual. The Sigma are generally superior overall to the Sony.
How should we say "Sony"?

No standard camera filter is good enough. You need a solar filter that is designed to block all the Ultraviolet and infrared or you will harm your eyes. Amazon.com has an excellent solar filter. 8"x8" Solar Filter Sheet for Telescopes, Binoculars and Cameras for 19.99 that is designed for solar eclipses. Any astronomy store will carry good filters. Don't count on camera stores. Your eyes are the only ones that you will ever have.

Thank you for the lead to Autopano Giga. I am not serious enough to make the jump to the next step. I am satisfied with the results I get with my in camera Sony a6000 and Lumix ZS100. For out of camera I use ArcSoft Panorama Maker 4. It give me the option of choosing the level of photos from 10MB to 30MB files or beyond. 30MB is about all my computer will handle. It is kind of kinky with the quality of the photos that I have taken, that is why I use the incamera panoramas. I appreciate the info that I get from UHH. Thanks, Tom