Tamron 70-300 first impressions and a question

[Photodude]

Hi All,


Got my Tamron 70-300 lens yesterday
With great trepidation put it on my D70
Was ready for the worse - cos had heard a lot of reports about purple fringing - chromatic abberations - softness on these forums
Snapped my first shots and ohhhhhhhhhhhhhhhhhh no - colours looked horrible!
Then discovered I had the white balance on tungsten light from my last session!

First impressions:

1. This things focuses near as quickly as the kit lens
2. Its plasticky - but so the camera body eh
3. Once I adjusted the white balance - everything looks preety good
4. Plenty of blur If ya not careful with camera shake - I suspect this is normal at 300 mm
5. Nice to have a longer lens again - I like the kit lens - but 18-70 is very restrictive

which brings me to a question

the exif data for my pictures states - for example - that at 70 mm the focal distance was 70 mm - is this really 105 mm?????

similarly the Tamron exif data states that Im at 300 mm fully zoomed - is ths really 450mm? etc etc

Cheers

John

[Greg B]

John

I have the same lens. And I am quite happy with it given that it cost <$250.

The EXIF data will show the actual focal length of the lens. The d70 has a "negative" size smaller than 35mm, so the multiplier (1.5) really means that the field of view of a 300 mm lens on the d70 is the same field of view as a 450mm lens on a 35mm camera.

cheers

[xerubus]

That is correct... the D70 has a FOV of 1.5.... so... 70mm x 1.5 = 105mm

[gstark]

the exif data for my pictures states - for example - that at 70 mm the focal distance was 70 mm - is this really 105 mm?????

similarly the Tamron exif data states that Im at 300 mm fully zoomed - is ths really 450mm? etc etc

What Glen said. The field of view is smaller, so you're seeing just a crop of what you might see when compared with a 35mm FF image.

But the focal length is still 70, 300, or whatever. If you look at your exif data for images made with the kit lens, you'll see exactly the same sort of results.

Enjoy the new lens.

[MHD]

*rant mode*
It still is a 70mm lens! Having a smaller sensor does not change the FL it changes the FOV which is an angular measurement
*/rant mode*

[MHD]

hehe... Gary and I ranted at the same time!

[Greg B]

I think it was only you who was ranting MHD

[Photodude]

Hang on this is confusing now

Is a 300 mm lens on a digital SLR = to a 450 mm on a 35mm SLR?????

[MHD]

The 300mm lens will and always will be a 300mm lens. However as you are only seeing 2/3 of the image a standard SLR sees you are effectively zoomed in more...

From the maxwell website (on the 300vr)
300mm

8° 10'
with film (F-series) SLRs
5° 20'
with Nikon DX Format
digital (D-series) SLRs


The reason why I am being pedantic is the FL effects more than the angular view (zoom) of the imaging system (and hence the image) It bears on the depth of field and light throughput as well...

[gstark]

Hang on this is confusing now

Is a 300 mm lens on a digital SLR = to a 450 mm on a 35mm SLR?????

Define "="

Seriously.

There's nothing that will make the 300mm lens be anything other than a 300mm lens.

But each lens produces an imaging circle, and the design of lenses for 35mm cameras is such that the imaging circle produced projects fully onto a frame sized for a full frame 35mm negative.

When you're using a Nikon DX sized camera, such as the D70 or D100, then you'll see that the frame size is smaller. That means that the image circle (which is still the same size) is oversized in relation to a DX frame, and some of that lens's projected image is, in effect, cropped out.

So, you're only seeing a part of the image produced by the lens, and some of it is, in effect, lost.

The key to understanding this is that, because this crop factor is 1.5, the end result that what you're seeing looks like you have zoomed further in. But no, you haven't; you're just seeing a tighter crop of the image.

Finally, the DX lenses produce a smaller imaging circle, and thus only work (effectively) on the digital cameras. But their focal length is still represented in terms of 35mm FF cameras, most probably because that's what we can all best relate to.


Does that help you understand this? (yes, it's a kind of difficult concept to wrap your mind around at first ...)

[Photodude]

soooooooooooo0000000000

What if i stickytaped a A3 sized poster to my back fence

Then mounted my 70-300 on my D70 and zoomed to 300 - approx distance of 20 metres

Then mounted the same lens on a film SLR and zoomed to 300 - from of cos the same distance

Would i see more detail from either camera?

If this is becoming tedious - please feel free to drop it

[gstark]

Would i see more detail from either camera?

If this is becoming tedious - please feel free to drop it

Good question, but I'm afraid it's the wrong question.

And no, it's not at all becoming tedious.


To answer your question, and with all things being equal, yes, you would see the same detail.

But things are not equal; on a film slr, you might have slightly higher resolution, and thus the level of detail - as resolved by the glass - might be higher on the film camera. That would certainly be my expectation.


But, as I said, that was not quite the correct question. Let's take your example, I'd like to rephrase it a little.

Let's start with your A3 poster, the 300mm lens, and a D70 on a tripod.

We'll mount the poster onto the fence, just as you have, but we're going to locate the camera so that, with the 300mm lens, the "image" of the poster fills the viewfinder.

So far so good?

Let's now remove the D70 from the tripod, and replace it with the film camera. Let's also put the 300mm lens onto the film camera. We need to take care to not move the tripod, and of course the poster remains firmly affixed to the fence.

So, the only real change is that we've swapped out the D70 for the film camera.

Now, let's have a peek through the viewfinder in the film camera.

Whereas before, we composed so that the poster filled the viewfinder, what we should now be seeing is an image whereby the poster seems to be smaller; it occupies a smaller portion of the total viewfinder area, and there are now parts of the fence visible in the outer edges of the viewfinder.

Effectively, you're looking at a greater image size with the film camera. No change in "detail", but certainly an apparent change in the visible content.

HTH.

[Photodude]

and when i looked through the viewfinder of the film slr - the poster would not occupy fully the viewfinder until i zoomed to 450 mm? (assuming the film slr had a 450 lens on it)?

[Matt. K]

Hey Dude!
What everybody has posted so far is correct...but to simplify it for you...a 300mm lens on a D70 has the same effect as a 450mm lens on a 35mm camera. More or less.

[Dargan]

Thanks for these explanatory replies Gary.

I was always uncertain about the references to 300mm=450mm in a Digital context. It seems apparent to me from your comments that the references to 1.5x factor are quite misleading but a convenient shorthand way of giving an answer to those questioning the nature of the digital sensor image from a D70 or other camera with less than 35mm sensor size. I am ploughing through Thom Hogans excellent book at present and examining these issues from a new perspective.

Can I prevail upon you to extend the discussion. With the smaller sensor of a D70, and using a 300mm lens (which I agree is still a 300mm lens - I have the Nikon 70-300G BTW) you identified less detail is likely than a film camera. This is because of sensor resolution potential I am assuming?

Are there other differences. Eg; Things appear sharper if you stop down (I may be getting this wrong but looking through a smaller circle at a distant object seems to increase resolution is the point I am making) ... So using the centre of a standard 70-300 mm lens rather than the full width of the lens may give better optics? I know my lens, the 70-300G is optimised for the size of the D70 sensor but with a film Nikkor lens would this create less chance for lens edge distortion etc.

Look, this is an inadequately phrased post but I guess I am just looking for more comment in this area. I like to understand the tool I am using and feel I need more clarification on this issue. Please excuse any unintended gaffes.

[gstark]

It seems apparent to me from your comments that the references to 1.5x factor are quite misleading but a convenient shorthand

That's quite true.

It's really a crop factor - think about taking any image, and cropping it somewhat, and then enlarging the resultant crop to the original size that you started with.

With the smaller sensor of a D70, and using a 300mm lens (which I agree is still a 300mm lens - I have the Nikon 70-300G BTW) you identified less detail is likely than a film camera. This is because of sensor resolution potential I am assuming?

Essentially, yes. I'm presuming firstly that film resolution is still higher with (for instance) low speed film than digital, and secondly that the images - both film and digital - will eventually break down, but in different ways: an image on film will break down into an even (more or less) grain pattern, whereas a digital image will break down into its component pixel patterns, which, although arranged evenly, are probably larger (ultimately) than grain particles.

That said, with good quality glass we're probably well into the realm of hair splitting. Literally.

I don't have a resolution chart, but it would be an interesting exercise to do, especially with a high quality B&W film. Two bodies (one film, one digital) one lens, a resolution chart, and a couple of hours playtime.

From a practical POV, I really wouldn't expect to see a whole lot of difference, btw, but ultimately, I'd expect the film to resolve more finely.

Are there other differences. Eg; Things appear sharper if you stop down (I may be getting this wrong but looking through a smaller circle at a distant object seems to increase resolution is the point I am making) ...

Yes, I would expect this to be the case, to a point. As you stop down, you're using the more central portions of the lens, and coming into what might be referred to as the lens's sweet spot.

Note that many lenses seem to work best between f8 - f11 - that's where their sweet spots are - and there's some element of degredation either side of those apertures.

Also, refer to last week's thread on DoF and digital cameras, and in particular to the discussion on circles of confusion. It bears some element of relevance to the questions you're asking.

So using the centre of a standard 70-300 mm lens rather than the full width of the lens may give better optics? I know my lens, the 70-300G is optimised for the size of the D70 sensor but with a film Nikkor lens would this create less chance for lens edge distortion etc.

Two points here.

First: yes, sort of. The D70 is using the centre of the image circle - not necessarily the lens.

Consider that if a particular lens exhibited good centre performance but, say, bad CA or vignetting towards the edges when used on a film body, that same lens would effectively seem to lose those characteristics when used on a digital body.

It's not that the characteristics are no longer there - they are - but that they've simply been cropped right out of the effective image circle that's being used. They're beyond your current field of view.

Second - you mention that the 70-300G is optimised for the size of the D70 sensor.

Is this true? The lens is a G series, which means that it has no aperture ring. But it's not a DX; it's a FF, 35mm lens.

I'm not sure that what you're saying here is correct.

Look, this is an inadequately phrased post but I guess I am just looking for more comment in this area. I like to understand the tool I am using and feel I need more clarification on this issue. Please excuse any unintended gaffes.

Please ask away; I love this sort of discussion.

[gstark]

and when i looked through the viewfinder of the film slr - the poster would not occupy fully the viewfinder until i zoomed to 450 mm? (assuming the film slr had a 450 lens on it)?

Pretty much, yes.

[Kristine]

Gary

This is the best forum. Where else would you get such great replies?

Thanks for your in-depth explanation on these issues. This kind of stuff gets confusing really quickly, but this discussion (in particular your responses) has clarified these issues alot for me.

Cheers
Kristine

[MHD]

The 70-300G is not a "specially designed for DX lens"

Those lenses are, suprisinglin enough, called DX lenses..

These lenses are and should be slightly cheaper than an exactly the same featured normal lens as they have a smaller circle and using them on a full frame/film body will usually result in vinetting

Thats one of the advanteges of the DX sensor... lenses that might be a little soft around the edges get better as you move away from those edges!

[Onyx]

Actually, the precise crop multiplication factor for DX format sensors has been quoted to be between 1.52 to 1.54x.

[Greg B]

Actually, the precise crop multiplication factor for DX format sensors has been quoted to be between 1.52 to 1.54x.

Can I have a guess?

I am going with 1.53

[Dargan]

Greg that's coz your just an average sort of guy.

Back to the discussion Gary.

DX lenses then should be cheaper as they have less of a FOV to cover I am assuming. Also the build requirements are less rigorous due to plastic construction and newer operational techniques, cheaper labour sources too I am assuming. This doesn't make them worse, but appropriate for the market they are intended for. In fact I assume that advances in lens design, manufacturing efficiencies and the requirements of Digital allow for cheaper but just as 'good' equipment.

In relation to this the notion of the 'circle of confusion' is important I think. There are some great discussions for those interested in this area to pursue, they are found on The Luminous Landscape and Thom Hogan's site that has some discussions as well. In particular 'Luminous Landscape' for me is my favourite as his (Reichenbach I think his name is) approach to photography is one I am attracted to. My understanding of the circle of confusion is that it is the point where our eyes resolve the dots that make up images that we create. I think monitor screens are 72dpi so our eyes don't need that much to create a viable image in our minds. In essence an argument is that the level of resolution that printshops look at is around 300dpi and when you look at the current capacity of a camera like the D70 which is overkill if you only print 6 x 4's you have to ask when enough is enough. I am all for quality and more pixels per dollar but how many of us are going to be blowing photo's of the family pet up to billboard size? IMHO the operational features of the D70 are what make it a stand out compared to others not its resolution per se. (The point BTW of my paragraph, note obtuse approach Gary)

My reading indicates that the D70 is appropriate technology at this point of time and so the DX lenses (and I will have to look up the exact meaning of the G series again but I think it simply hands over some of the adjustments to the camera body) are good value for users. Note the increase in profits by Nikon this year, due no doubt to hitting the market with exactly the right product at the appropriate time.

Let's get back to some semblance of the theme here. If we are just using the centre of other older film second hand lenses or even newer cheaper DX lenses we are looking at even more arguments that underpin the value of our choice of the D70 as a camera body. Either way I think we are getting even better value out of a great camera, that is still keeping my interest the further I explore.

[gstark]

DX lenses then should be cheaper as they have less of a FOV to cover I am assuming. Also the build requirements are less rigorous due to plastic construction and newer operational techniques, cheaper labour sources too I am assuming. This doesn't make them worse, but appropriate for the market they are intended for. In fact I assume that advances in lens design, manufacturing efficiencies and the requirements of Digital allow for cheaper but just as 'good' equipment.

They should be smaller and lighter. Basic construction techniques and materials should be no better, nor any any worse, than other lenses, depending upon the intended target user.

The kit lens, as good as it is, is targetted at the serious amateur, whereas lenses like the 10.5 and 12-24 seem to be aimed more at the pro market.

But smaller and lighter should also equate to less expensive.

IMHO the operational features of the D70 are what make it a stand out compared to others not its resolution per se. (The point BTW of my paragraph, note obtuse approach Gary)

I can't disagree.

And what you're saying about how much resolution is enough is a valid point. That's why the D2h has only 4MP: its target is mainly sports press photographers. How big are those images likely to end up ?

Let's get back to some semblance of the theme here. If we are just using the centre of other older film second hand lenses or even newer cheaper DX lenses we are looking at even more arguments that underpin the value of our choice of the D70 as a camera body. Either way I think we are getting even better value out of a great camera, that is still keeping my interest the further I explore.

Again, I cannot disagree.

[gstark]

Greg,

Actually, the precise crop multiplication factor for DX format sensors has been quoted to be between 1.52 to 1.54x.

Can I have a guess?

I am going with 1.53

In all seriousness, I suspect you'd be wrong.

The sensor sizes on the various camera models is, in fact slightly different, and 1.5 is a rough estimation in terms of the DX sensor size in general.

But if you review the actual specifications across the differnent models, you will see what I mean.

[gstark]

Kristine,

Gary

This is the best forum. Where else would you get such great replies?

Thanks for your in-depth explanation on these issues. This kind of stuff gets confusing really quickly, but this discussion (in particular your responses) has clarified these issues alot for me.

Cheers
Kristine

Thanx.

It's active discussions such as these that make this whole thing worthwhile, I believe.

[Onyx]

http://www.bythom.com/dslrcompare.htm

1.52 to 1.54x.