Q. 300mm or 200mm?

[Val]

Hello everyone, first I want to introduce myself. My name is Val.
I live in Brooklyn, NY for the past 12 years originally I am from Ukraine.
A month ago got myself into a new hobby and bough S2.

Few days ago got myself Tamron 28-300mm XR after reading a lot about it online.
As I can remember someone said that some lenses are not 28-300mm even though it is says so but in reality 28-200mm, so my question is since I don?t have any other 300mm lenses is there any ways to check if its really 300mm. One more thing when I take a picture at 300mm in the file info it is says focal length 299mm.

Thanks in advance
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[Swampy]

Welcome to the forum Val. I think you may be having problems understanding crop factor, not that the lens is not 300mm. The lens you have is truely a 28-300mm lens, on a film camera. On our S2 however, the CCD is smaller than a 35mm frame which causes a crop factor to be thrown into the mix of things. Our crop factor is 1.5x, so you can take any number mm lens you want and multiply it by 1.5x and you'll have what the lens will really be.

So, your 28-300mm lens will look and act like a 36-450mm lens. A 60mm lens would be 90mm and so forth.

The file info loses something in the calculations sometimes, so it may show 1mm off depending on the lens. Or, you may have been zoomed in to 299mm on the lens and just didn't know it. Maybe. But I know the camera and software will make calculation errors like this, so I wouldn't really worry about it. My Nikon 50-300mm lens shows up as 299mm, my Nikon 60mm shows as 59mm, but my 70-200mm VR shows 70 or 200 if I'm at either end, and I'll just assume it's showing the correct focal length if I'm in the middle. I think my 50-500mm Sigma also reads correctly if I'm not mistaken too.

Hope this helps ya.

[Tom V]

Right.

The digital camera's smaller sensor sees only the center of the image that the lens was designed for (full 35mm film format). Since the sensor format is 2/3 the size of film format, the lens seems to behave, and create images that are equivalent of a focal length 3/2 longer. This is the 1.5 X factor used to calculate the effective focal length comes from. Your 300mm lens really s 300mm, but it will seem like 450mm.

Now that I said your lens is really 300mm, it might really only be 299mm or 302mm or 296mm. Lens manufacturerers give themselves a little tolerance when designing lenses, and sometimes a lens design mathematically works out to 298mm, but they will market it as a 300mm. The data stored with the file may indicate that the lens was set to 300mm, but that data is just taken from some sort of sensor in the lens that indicates what the focal length or where in the zoom range the lens barrels were set. There is nothing really optically exact about it, and the camera really has no way of knowing other than what the lens "tells" it.

The camera never lies, but the lens might.;)

[Val]

Thank you Swampy and Tom for your replies.

I understand that S2 has a 1.5 multiplier and that my 28-300mm will act like 36-450mm, but is there a way to check lets say all the way out to 300mm (450mm) it is in fact 300mm (450mm) and i am not talking about + or - 5-10mm diff., i am talking about 100mm diff.
I read somewhere that a guy bought tamron 28-300mm XR and when he compared it at 300mm to his other 300mm lens, Tamron appeared to be 28-200mm in reality even though on the lens it self was written 28-300mm.
Since i have no other 300mm lens i was wondering if there is some other way to check that.

Thanks again.
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[CaptJR]

Val
Welcome to the forum. I would think you should be able to chech that big a difference anywhere on the scale. So if you have a 60mm prime for example, shoot a picture with it. Then use your 28-300mm and set it to 60mm. If it is fairly similar then I'd guess that your 28-300mm is exactly that. This could be done with any other lens that has an availiable setting between 28 and 300mm.

JR

[Val]

Thanks for your reply CaptJR.
I have 50mm nikon lens, and i'll try that.
Thnks again.
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[indysteve]

Val,

If you have a 50mm then there might be another way to compare to double check the 300mm. Take two pictures one with the 50mm and the other with the zoom at 300mm, try to keep the centers of each picture roughly the same. Use a low resolution (we're looking for magnification not picture quality) but the same for both pictures.

Use PS and resample the 50mm picture six times wider than its default. then copy and paste the 300mm into the new 50mm picture. If the magification is correct (300mm) then you should be able to align the two pictures. It won't be perfect but it should do the job for comparision sake.

Steve

[Val]

Thank you indysteve for your reply.

I tried it all, but still something does not look right or maybe its just me.
All the tests I did the camera was on a tripod about 3-4 feet away from the object, maybe i should have messured the same distance from the lens to the object and not from the camera.
In any case if anyone can, please help me.

Sorry for not sharp images.

Here is 1st shot at 50mm

http://www.s2pro.com/gallery/data/511/1231DSCF0828.JPG

2nd at 100mm

http://www.s2pro.com/gallery/data/511/1231DSCF0829.JPG

3rd at 200mm

http://www.s2pro.com/gallery/data/511/1231DSCF0830.JPG

4th at 300mm

http://www.s2pro.com/gallery/data/511/1231DSCF0831.JPG

Here I put two shots together to compare, both are at 50mm, one is nikon 50mm f/1.8 and another is tamton 28-300mm XR.

http://www.s2pro.com/gallery/data/511/123150-50comp.jpg

Any thoughts???

Thanks again
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[indysteve]

Val,

Wow!, I agree that based on your results, it doesn't look right.

Question: is the first picture with your prime lens, or 50mm estimated on the zoom?

I know from experience that focus makes a little difference (but not much) to the magnification so the 50mm picture could be off slightly, but not as much as it seems.

I left my camera and primes at the office today, so I can't try anything tonight. I'll try some things over the weekend.

By the way, after I first saw your post today, I laid the lens angles out in CAD and verified that I wasn't going crazy (it should work).

As far as the 50mm to 50mm comparision, to me it looks like one is slightly more than magnified than the other, if this was the comparison between prime and the zoom, there could be some error in where the mark is on the zoom. I don't have any experience (never saw a need to measure) with how accurate the intermediate marks are on zooms.

My original thought process trying to compare the magnification was never meant to be perfect, I expect differences in lens distortion to prevent the two images from lining up perfectly, but I think the 50 to 50 should be closer

Finally, I could be completely wrong in my thought process here (wish I had my camera).

Can someone else help out here? Is my re-sampling thought process sound? Or have I led Val down the wrong road?

Steve

[Igor]

Val,
here's a photo of a 50mm lens and four AA's taken with my 300mm lens at 2 meters precisely (from a camera lens mount surface), then resized to 600x400 pixels. Do the same and compare the two shots.

Hope this helps,

[Val]

WOW, What a difference, not even close, i think i better go to the store and exchange it before its too late.

http://www.s2pro.com/gallery/data/500/1231300mm_at_2_meters_600pixels_wide_Val.jpg
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[RedSlug]

I wonder if this is the reason my shots of the moon (see other thread) are a lot smaller than others shot at 300mm :confused:

I think I will try this test later on.

[Val]

Just got a new one Tamron 28-300mm XR
Results are the same.
What can be wrong?
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[Igor]

Val,
just finished another test shooting. Used all my 300mm lenses:
300mm ed af 2.8, 70-300mm d and 80-400mm VR.
Shoot the same 50mm lens with batteries at 3 meter distance (minimum focusing distance for the 300mm /2.8).
Check the results below:

1. 300mm /2.8

[Igor]

2. 70-300mm

[Igor]

3. 80-400mm VR at 300mm

[Val]

Thank Igor for your help and replies.

That was a good test, looks like your lenses are all the same at 300mm.

Tried the test again at 300mm comparing to your images and at 50mm with nikon 50mm f/1.8, and still its off.

Going to try calling Tamron monday, we'll see what the have to say about it, hopefully they will solve the problem.

Thanks again to everyone.

ps.
I'll let you know what happens.
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[Val]

Just came back from Tamron service dept. The guy was very nice to me and was willing to check the lens without an appointment or any questions. After a quick check, he suggested that if I am still unsatisfied with the lens, I can leave it or even ship it to him for further testing. The service was excellent.

He told me that there is an industry allowance of +/- 5%, in other words if you have a 28-300mm lens and it tests 28-285mm, it's ok to call it 28-300mm. Also he said when you want to compare to zoom lenses they must be set to infinity to get an accurate measurement due to internal focusing. Therefore the pictures may not be identical but within the -/+ 5%.

I am still thinking whether I should keep the lens or exchange it for something else, maybe 24-120 VR.
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[Igor]

Val,
I do recommend you to get the 24-120 VR instead.

[Val]

Returned my Tamron 28-300mm XR today, well what can i say, read and understand the store policy before doing business.

The guy at www.abesofmaine.com gave me hard time getting full credit for it, but he did at the end. I don't recomend dealing with them.
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