A quick way to figure zoom in 3x/4x etc to mm (1 Viewer)

[YellowBudgie]

I thought I saw someone mention this on this forum but I can't find it in a search. Owning digital camera's that are rated in X max zoom I find it hard to convert what that would be on a DSLR lens since they use mm to rate the lens. Is there any rough way to multiply mm x (something) = zoom factor? or is there a chart someplace?

Thanks!

 

[Keith Reeder]

1x magnification is roughly equivalent to 50mm, so a 1 - 3x zoom would be about 50 - 150mm.

 

[YellowBudgie]

1x magnification is roughly equivalent to 50mm, so a 1 - 3x zoom would be about 50 - 150mm.

Thanks! I always wanted to know when just browsing the DSLR's at the store what the mm really equaled in my experience.

It's a little dissapointing in a way because I was at my favorite wild birding place and there was someone there with a decent DSLR, Doubler and expensive looking telephoto lens. He was looking at my amature shot of a golden finch taken with my A95 and 8x add on lens shoot through a window. He was surprised at the quality of the photo. I was telling him how I wanted to get into digiscoping once I can afford a nice scope.

He was a nice helpful guy and mentioned the nice options of the DSLR, which I knew about and drooled over when looking at the $3000 models of Nikons. He said this lens and doubler shoots up to 300mm which did not mean much to me at the time.

So now I know he was shooting up to 6x. I was shooting at 24x (3x x 8x). 24x is short of what I need to frame a small bird like a finch at our feeders. I think 30x to 35x would be perfect for this. The photo I took was shoot at about 12x to 18x from just 6 feet away to frame the golden finch. At 24x from 6 feet I can photo a finches top half and maybe his head. I can't get the camera noise level down shooting outside at maximum zoom with the 8x add on so a nice scope will be great.

I was going to price out a DSRL with a doubler and a telephoto lens that would shoot like my setup and assumed 300mm was further.

If anyone with DSLR experience can help me understand this. How are people getting such great shots with a DSLR 300mm lens beeing the average I see out there. I know getting close to a bird via a hide is one option and shooting with a high mm lens with a doubler is another option. Are most people shooting birds with a higher mm lens, doubler and using high pixels and raw to crop the bird out of the photo? In the future I'm looking for my final result to be a full glossy 8x11 photo of a closely framed bird if I was to get a DSLR.

Now I'm at the point where I don't know if I should get a nice high quality birding scope that would be dual use or save for a longer time and go the DSLR route.

 

[andrew_s]

1x magnification is roughly equivalent to 50mm, so a 1 - 3x zoom would be about 50 - 150mm.

Which is true, but not what the 3X zoom marked on a camera means.

3X means that the telephoto end of the zoom has 3x the focal length of the wide end of the zoom.

In the case of the A95, the true focal length range of the 3x zoom lens is 7.8-23.4mm, and the 35mm equiv focal length is 38-114mm, giving a maximum apparent magnification of 2.3x.

That's a conversion factor of 4.9. DSLRs have a bigger sensor that's closer in size to a 35mm frame, so the conversion factors are mostly between 1.5 and 2 (1.6 for Canon 300D/digital Rebel).

Your photos with the 8x converter are at 2.3 x 8 = 18.4x
To get the same size image on a Canon 350D would need a (18.4 x 50 /1.6 =) 575mm lens, so a 300mm + 2x converter is about the same.

Bear in mind that converters magnify any image defects as well as introducing some of their own, so a lens + converter is always going to produce a worse image than a lens of equivalent focal length unless there's a sizeable difference in the base lens quality.

 

[YellowBudgie]

Which is true, but not what the 3X zoom marked on a camera means.

3X means that the telephoto end of the zoom has 3x the focal length of the wide end of the zoom.

In the case of the A95, the true focal length range of the 3x zoom lens is 7.8-23.4mm, and the 35mm equiv focal length is 38-114mm, giving a maximum apparent magnification of 2.3x.

That's a conversion factor of 4.9. DSLRs have a bigger sensor that's closer in size to a 35mm frame, so the conversion factors are mostly between 1.5 and 2 (1.6 for Canon 300D/digital Rebel).

Your photos with the 8x converter are at 2.3 x 8 = 18.4x
To get the same size image on a Canon 350D would need a (18.4 x 50 /1.6 =) 575mm lens, so a 300mm + 2x converter is about the same.

Bear in mind that converters magnify any image defects as well as introducing some of their own, so a lens + converter is always going to produce a worse image than a lens of equivalent focal length unless there's a sizeable difference in the base lens quality.

Thanks! I have not read up on the technical photography terms as far as lenses go that you explained here so well. If I did read them in some book I would have most likely gotten more confused Thanks for using my camera as an example to explain this.

I think I may try the digiscoping technique first since I enjoy watching birds as well and would have the scope for that.

I would still like a DSLR one day and can continue to save up while I shoot with my A95 and Nikon CP8400. I'm learning the fundamentals of operating a DSLR with the CP8400. If I can get good with that camera and learn good photography techniques the learning curve when purchasing a DSLR would be less.

Thanks again!

 

[RAH]

Concerning the conversion factor for DSLRs - I think the easiest way to figure it is to first convert the lens mm, then divide by 50. For example: a Canon 350D has a factor of 1.6. So a 300mm lens on a 350D is equivalent to a 480mm lens (300 x 1.6). Then, to get the power, divide by 50 (480/50 = 9.6x).

After doing all this math and looking at the lenses available for DSLRs and their cost, you now see why people use digiscoping if they want REALLY high power. This is not to say that the results are nearly as good as pictures taken with a DSLR and a good lens.

Finally, I do think that you are correct that many bird images you see on the web are heavily cropped to make the bird fill the frame. After cropping, many could not be printed very large at all. But then again, some folks are expert wildlife photographers and do know how to get really close, which is required for a high resolution picture of a very small bird.

 

[YellowBudgie]

Concerning the conversion factor for DSLRs - I think the easiest way to figure it is to first convert the lens mm, then divide by 50. For example: a Canon 350D has a factor of 1.6. So a 300mm lens on a 350D is equivalent to a 480mm lens (300 x 1.6). Then, to get the power, divide by 50 (480/50 = 9.6x).

After doing all this math and looking at the lenses available for DSLRs and their cost, you now see why people use digiscoping if they want REALLY high power. This is not to say that the results are nearly as good as pictures taken with a DSLR and a good lens.

Finally, I do think that you are correct that many bird images you see on the web are heavily cropped to make the bird fill the frame. After cropping, many could not be printed very large at all. But then again, some folks are expert wildlife photographers and do know how to get really close, which is required for a high resolution picture of a very small bird.

I decided to go the digiscoping route first since I don't own a nice spotting scope for bird/nature viewing. In the future I can save up and buy the DSLR and nice lens. I enjoy photography in general so both ways would be nice. The DSLR would be great for those quick shots when you are not setup with your digiscope and the photography that does not require such a long range.

I spoke to someone at Swarovski and he had an interest in starting photography and was thinking of getting a camera to digiscope. I told him about birdforum and steves digicams. I told him I had a A95 and sent him some good photos I was able to take with it with the 8x add on.

He was also a hunter and would setup hides in the wild and would say that when you do a good job at hiding yourself nature surrounds you. He wished he had a regular camera since wild animals would get so close to him a long range lens wasn't needed. The way he explained it sounded very nice. I don't hunt but trying that one day with a camera would be great.

Thanks

 

[gmax]

Concerning the conversion factor for DSLRs - I think the easiest way to figure it is to first convert the lens mm, then divide by 50. For example: a Canon 350D has a factor of 1.6. So a 300mm lens on a 350D is equivalent to a 480mm lens (300 x 1.6). Then, to get the power, divide by 50 (480/50 = 9.6x).

After doing all this math ...

I'm not very good at math, but what I know re. P&S cameras is that when I bought my Canon IS S1, I was told that its 10x magnification was roughly equivalent to a 380mm lens (and that its sister S2 - a 12x - was ca. 420mm) ...
hope it helps
Max

 

[gordon g]

1x magnification is roughly equivalent to 50mm, so a 1 - 3x zoom would be about 50 - 150mm.

Strictly speaking that's only true for full frame 35mm cameras. The 1.6 crop sensor cameras tend to quote 35mm equivalent focal lengths so as not to confuse us by using a different focal length for the same field of view!

 

[YellowBudgie]

I thought I saw someone mention this on this forum but I can't find it in a search. Owning digital camera's that are rated in X max zoom I find it hard to convert what that would be on a DSLR lens since they use mm to rate the lens. Is there any rough way to multiply mm x (something) = zoom factor? or is there a chart someplace?

Thanks!

When you get a high end scope like a Swarovski STS 80 HD and a 20-60xS Eyepiece are those X factors more true to life?

 

[gordon g]

When you get a high end scope like a Swarovski STS 80 HD and a 20-60xS Eyepiece are those X factors more true to life?

I think they represent the magnification over the naked eye view.
In 35mm format the naked eye view is roughly equivalent to a 50mm lens - hence a lot of the maths mentioned ealier.

The swaro 80HD + 20-60zoom is a superb scope. I have one myself and cant fault it.

 

[Keith Reeder]

Strictly speaking that's only true for full frame 35mm cameras. The 1.6 crop sensor cameras tend to quote 35mm equivalent focal lengths so as not to confuse us by using a different focal length for the same field of view!

Aye - actually I used to suggest 38mm as the 1x equivalent, which exactly corresponds to Max's Canon S1.

 

[RAH]

I'm not very good at math, but what I know re. P&S cameras is that when I bought my Canon IS S1, I was told that its 10x magnification was roughly equivalent to a 380mm lens (and that its sister S2 - a 12x - was ca. 420mm) ...
hope it helps
Max

Max, the 380mm is NOT equivalent to 10x. The reason is because the "10x" lens on the S1 camera starts at a somewhat wideangle of 38mm equivalent. It does not start at 50mm equivalent. In other words, the 10x total zoom covers wideangle thru telephoto. Same with the "12x" S2 - the 420mm is not 12x either, since the zoom range starts at wideangle.

The 380mm is 380/50 = 7.6x
420mm is 420/50 = 8.4

 

[gmax]

Max, the 380mm is NOT equivalent to 10x. The reason is because the "10x" lens on the S1 camera starts at a somewhat wideangle of 38mm equivalent. It does not start at 50mm equivalent. In other words, the 10x total zoom covers wideangle thru telephoto. Same with the "12x" S2 - the 420mm is not 12x either, since the zoom range starts at wideangle.

The 380mm is 380/50 = 7.6x
420mm is 420/50 = 8.4

... but when we are referring to 35mm cameras what does happen? I know that the human eye sight is roughly equivalent to a 50mm, but when we use figures like 3x, 10x, on P&S cameras, or 40 - 60x on digiscopes are we speaking the same language? Reference to magnification is therefore deliberately misleading?
Getting confused :h?:

 

[gordon g]

... but when we are referring to 35mm cameras what does happen? I know that the human eye sight is roughly equivalent to a 50mm, but when we use figures like 3x, 10x, on P&S cameras, or 40 - 60x on digiscopes are we speaking the same language? Reference to magnification is therefore deliberately misleading?
Getting confused :h?:

In short - yes it is! It is not clear exactly what is being referred to. Often, when a zoom range is given eg 3X, what is meant is that the lens will zoom out to 3X the shortest focal length. As was pointed out by someone else, that may not be the same thing as magnification factor, which I think is what the scope eyepieces quote.
It would actually be more sensible to give field of view figures, as these would allow just this sort of comparison across formats and platforms. :h?:

 

[colonelboris]

Maybe tabulate these figures for point and shoots and mke a graph - should give a rough and ready estimate.
I'd do it, but I'm fundamentally lazy...

 

[RAH]

... but when we are referring to 35mm cameras what does happen? I know that the human eye sight is roughly equivalent to a 50mm, but when we use figures like 3x, 10x, on P&S cameras, or 40 - 60x on digiscopes are we speaking the same language? Reference to magnification is therefore deliberately misleading?
Getting confused :h?:

When you see "3x" or "10x" on a P&S, it is giving you the total range of the zoom lens, not the highest magnification. In the case of a 38 to 380 equivalent "10x" lens on the S1, the range is from about -2 to +8 magnification - hence "10x" total. Yes, it is misleading.

Many folks are disappointed by the low magnification of a standard "3x" P&S, expecting 3 power to get them more magnification. It's the same thing - the lens is going from wide-angle (less-than-naked-eye magnification) to a little more than naked-eye-magnification - maybe about -1.5 to +1.5 . Hence the total "3x".

 

[YellowBudgie]

When you see "3x" or "10x" on a P&S, it is giving you the total range of the zoom lens, not the highest magnification. In the case of a 38 to 380 equivalent "10x" lens on the S1, the range is from about -2 to +8 magnification - hence "10x" total. Yes, it is misleading.

Many folks are disappointed by the low magnification of a standard "3x" P&S, expecting 3 power to get them more magnification. It's the same thing - the lens is going from wide-angle (less-than-naked-eye magnification) to a little more than naked-eye-magnification - maybe about -1.5 to +1.5 . Hence the total "3x".

Its nice to hear about for me owning the camera's I have. I'll know in the future when getting a DSLR that it's lens will give me more than I thought currently. It makes getting a DSLR for bird photo's sound like something I would like to do one day.

I just put in an order for a Swarovski STS 80 HD, 20-60 Eyepiece and
Swarovski Digital Camera Base. I'm going to see how this works out with my 2 cameras. I hope it works out well.

I may get a fixed lens and the DCA for my Canon A95 in the future for a nice tight fit. I have trouble with my hands and don't want to be removing the DCA and adjusting the zoom frequently so I may opt for a fixed lens. When I know what range I shoot at and how the Canon A95 can perform with noise I can decide on a 20x or 30x fixed lens. I can always bring it all with me.

Does anyone know what magnification the Canon A95 will go before running into noise issues from the external scope with minimum zoom?

Thanks,