was_a_guru

I will be going an a trip/tour to Costa Rica in March.

I will taking my D7500 with my Tamron 18-400 lens. But I would like to have a focal length (600-800?) capability as well (rental).

I thought about a teleconverter but haven’t see any one that would work. Nikon ones are for Nikon lenses only and the two Tamron offerings only work with specific Tamron lenses - not mine.

Unless someone knows of a teleconverter that would work I have three options.
1. Rent a Nikon teleconverter and also bring my Nikon 70-300 lens. Relatively inexpensive.
2 Rent a Nikon longer (>400) telephoto lens. Very expensive.
3. Rent a Tamron longer (>400) telephoto lens. Less expensive than #2 more expensive than #1.

Any thoughts or suggestions? Thanks.

CHG_CANON Loc: the Windy City

Your 70-300 is not candidate for a Nikon teleconverter, check the details on the compatibility charts for the teleconverter model(s). Third-party extenders work best when paired the the highest quality third-party lenses of the same vendor. What do you envision shooting at lengths greater than 400mm? Low-light under the forest canopy will challenge lenses with max apertures smaller than f/5.6, whether extended or not.

Elmerviking

Your Tamron 18-400 mm will have a field of view same as a full frame 27-600 mm lens. Isn’t that enough?
Cropping will do the rest!

mas24 Loc: Southern CA

The Tamron 18-400mm is a crop sensor designed lens that is selling fast at about $649 now. A bargain IMO. That lens will give you a field of view of 600mm, as previously stated. Why would you want more? Unless you buy an aftermarket teleconverter, you will find that the Brand Name teleconverters are not inexpensive. If you had a Nikon lens with a Nikon camera, certain Nikon lenses would work with a Kenko Brand name 1.4X teleconverter. Don't even consider a 2.0X. Good luck.

was_a_guru

Thanks, but now I’m confused. That lens is advertised as being for a APS-C (crop sensor) Nikon. So the image projected on the sensor is the same size as the sensor so shouldn’t it be just 18-400 as opposed to a full frame lens which projects a larger image on the crop sensor thus an greater equivalent focal length?

mas24 Loc: Southern CA

If you use a full frame lens on a full frame camera. You get the same image as it would be on a 35mm SLR film camera. If your Tamron 18-400mm lens was a full frame format lens. You would not have a 1.5X factor, as you would on a crop sensor. That's how you get a field of view of up to 600mm on the Tamron lens you have. Canon crop sensors have a 1.6X factor. So, if you owned a Canon crop sensor DSLR. You would have a longer field of view. It would be 29-640mm. On some Nikon full frame cameras, you put a crop sensor lens on them. And put itt in DX mode. Not recommended. Full frame cameras deserve full frame lenses

was_a_guru

So when I bought the Tamron I did a test, mainly for quality, comparing it to the two kit lenses (18-50 & 70-300) that came with the camera. With the camera on a tripod I took a series of shots at 18, 35, 50 & 70, 100, 200, 300, & (400 - Tamron only).

Attached are the shots taken at 300 for Nikon and Tamron. The field of view is near identical on both of them (that is the case for all of the respective shots). So either the Nikon 70-300 is really a 105-450 or the Tamron is really an 18-400. The metadata shows 300 for both.

Attached file:
(Download)

Attached file:
(Download)

WJShaheen Loc: Gold Canyon, AZ

Agree wholeheartedly on using the Kenko 1.4x. Good image quality and the extended FL and f/r are properly recorded.

ekfelton Loc: Michigan

Will this be your only trip to Costa Rica? If so rent the best lens you can afford. You don’t want to return from your trip wishing you had a longer/ better lens.

david vt Loc: Vermont

Nope. You’re not quite getting it. It is NOT the lens, the crop factor is in that you are using an APC camera body - your D7500. With a crop BODY, you are getting a FOV equivalent of 1.5x of a old 35mm film camera. It does not matter, in terms of the crop factor, if you are using a DX or FX lens - the CF is determined by the body, and it happens that a FF BODY matches the old 35mm film size (and why it is known as FF).

So, your next question is that if does not make a difference in Field of View between a FF and DX lens, why are there both? It has to do with the maximum size of the image circle that can hit the sensor. The FF lens has a larger image circle hitting the sensor than a DX lens. So, if you use a FF lens on a DX body, no problem. The larger image circle is just outside the sensor. No harm, no foul. However, if you use a DX lens on an FX body, the image circle can be too small, resulting in vignetting at the corners of the sensor.

Hope that helps. You can google DX lens on an FX body for more info, or search past threads here in UHH archives. Some of our folks have posted nice images and diagrams explaining.

Bottom line, on your APX D7500 crop body, the 1.5x CF is applied to ALL lens, and this is why you did not see a difference in your test in terms of FOV and “equivalent” length.



The

WJShaheen Loc: Gold Canyon, AZ

[quote=david vt]Nope. You’re not quite getting it. It is NOT the lens, the crop factor is in that you are using an APC camera body - your D7500. With a crop BODY, you are getting a FOV equivalent of 1.5x of a old 35mm film camera. It does not matter, in terms of the crop factor, if you are using a DX or FX lens - the CF is determined by the body, and it happens that a FF BODY matches the old 35mm film size (and why it is known as FF).

So, your next question is that if does not make a difference in Field of View between a FF and DX lens, why are there both? It has to do with the maximum size of the image circle that can hit the sensor. The FF lens has a larger image circle hitting the sensor than a DX lens. So, if you use a FF lens on a DX body, no problem. The larger image circle is just outside the sensor. No harm, no foul. However, if you use a DX lens on an FX body, the image circle can be too small, resulting in vignetting at the corners of the sensor.

Hope that helps. You can google DX lens on an FX body for more info, or search past threads here in UHH archives. Some of our folks have posted nice images and diagrams explaining.

Bottom line, on your APX D7500 crop body, the 1.5x CF is applied to ALL lens, and this is why you did not see a difference in your test in terms of FOV and “equivalent” length.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

I guess I'm confused, but that does not take much. If you have a D7500, and are unfortunate enough to own a Tamron 18-400, your lens will have an equivalent field of view of 600 at the top end of your lens, will it not? Why would you even need a tele extender.
There has not been a teleconverter made that improves or even maintains image quality. And besides, I believe your lens at 400 is at an f stop of 6.3, wouldn't a tele converter take you beyond f8 resulting in non auto focusing on your D7500, or would that one stop bring you to f8. Just not sure.
I would go with your D7500 and the unfortunate Tamron 18-400.

imagemeister Loc: mid east Florida

imagemeister Loc: mid east Florida

.......use a monopod, facial stabilizers, lower your ISO and motion blurring, and CROP - and use well applied pixel enlargement software if needed for larger printings.

mas24 Loc: Southern CA

Yes. I got the Kenko 1.4X teleconverter for my Nikon for about $150, new in the box. I don't use it a lot though. It works well.