Curious Conundrum Nikon lens Metrics

As mentioned in previous posts, I recently bought a used D7200. Primary motivations were to take advantage of the extra reach that camera would give me with my long FX lenses for wildlife, and secondarily, to have a less expensive and also lighter kit for any excursions that might put the gear at risk. The camera came with the latest 18-55, and I found and purchased an inexpensive 55 -200. I had very good results with earlier models of the same lenses on my D 60, and these proved to be even better. Here is the question. When I check image EXIF data for DX lenses on a DX camera they show the same 1.5 factor I expected with FX lenses. In 35mm equivalent DX 18mm = 27mm all the way up to DX 200mm, which equals 300mm. Bottom line, why aren't the lenses marked to show the FL they actually render? I probably "missed a turn on this issue", or am a little slow today, there is likely a simple explanation?

My D200 didn't and my D7000 doesn't. Maybe a new setting?

Those DX lenses are marked to show their actual focal length. We need to keep in mind that the focal length for the 35mm/FX format is not some kind of "standard." 35mm was the most popular format from the 1960's to probably early this century when 35mm film was popular, and most people are familiar with focal lengths associated with the 35mm format. However, today, mobile phone cameras are probably the most popular cameras.

35mm/FX format is not some kind of "standard."

Thanks - so except as a point of reference for those of us who grew up with film, it is irrelevant.

I always hate the use of 35mm equivalent and crop factor but I realize that if I am looking at bridge camera or point and shoot it's very difficult for me to determine the angle of view or field of view range of the lens without the 35mm equivalent. The sensor size of these cameras are difficult to find.

In EXIF data, there are 2 values for focal length: the actual focal length, and the "35mm equivalent focal length". Seems like the software you use displays the latter?

so except as a point of reference for those of us who grew up with film, it is irrelevant.

Yep. Nikon for some reason decided to have both information in their EXIF data (can't recall though when that started): the actual focal length used and its film-equivalent. At some point, some camera makers have put both information directly only the lens - I believe (but am not sure) that this practice has now ceased. Here's an image of the Sony R1 that has the actual focal length written at the front of the lens but the zoom ring displays the 35mm-equivalent focal length. Thankfully, since with a crop factor of about 1.68, the calculation wasn't as easy as with Nikon's (and others) standard crop factor of about 1.5x.

Yes, but my interest was in the effective focal length - how a 200 mm DX lens would be shown at 35mm equivalent 300mm the same as a 200mm FX Lens. Puzzling, no actual problem.

Sandy: it's not a function of the lens. An 85mm DX lens (say, the micro Nikkor) and an 85mm FX lens (the f/1.8 and 1.4 lenses) have the same focal length, and the same equivalent focal length.

 

I've not checked, but I'm reasonably sure that putting my D810 in DX crop will change the "35mm equivalent" number - and I'd also expect the same to apply to the 1.2x crop mode (which I use on the D810 because it gives me 6fps at 25MP rather than the ~15MP of the DX crop), and also the higher crop factor option on some DX bodies (such as the D7100). I'd guess the same from the 1 series, including lenses on the FT-1.

 

There's no practical way to label all of these factors mechanically, especially when making it practical to compare current lenses to ones that eye created before DX existed. As Wouter said, Nikon just encode both actual and 35mm equivalent values in the EXIF. And of course it's all broken the moment you crop the resulting image yourself anyway. :-)

How and when did the crappy quality of 35mm film ever become any sort of 'standard'?

 

It was, and still is, of barely acceptable image quality. Time was - not so long back - when no picture library would take it.

 

Surely a 'standard' should imply a certain degree of quality? Not the fact that fairly undiscerning masses bought into it in the millions.

How and when did the crappy quality of 35mm film ever become any sort of 'standard'?

Well, it is and was what it was - used by a book full of successful professionals for everything from architecture to zoology. Understanding that at times larger formats were more useful or effective, I'd wager that more 35mm format images were purchased and published than the rest combined. In some cases, the particular "look" of film, hard to duplicate with digital (IMO) is still very evocative. I can appreciate your aversion, RJ, tho many of us may not share it.

Surely a 'standard' should imply a certain degree of quality? Not the fact that fairly undiscerning masses bought into it in the millions.

 

That's not really how standards have ended up working. :-)

 

Let's see. Digital storage which measures how fast it can transfer data in terms of the audio rate of a CD? The VHS vs Betamax wars?

? The NTSC colour gamut. YUV. GIFs... No, I'll go insane if I go through the list of every annoying thing that got standardised, because I work in a standards body, and I'm in danger of letting people see behind the magic curtain. Too many things happen because everyone wants to leave.

To be pedantic, I'm not sure how precisely defined the film frame area is. Certainly I've had a fish eye lens with coverage designed to allow for losing some film area to slide mounting. I don't believe all full-frame DSLRs have the same exposure area (dpreview currently lists the D850 as 35.9x23.9mm and the D810 as 35.9x24mm, for example).

 

I have quite a few rolls of 35mm film in my fridge (plus several developed ones). I might use them up at some point, but I've got to say I'm not hugely enthused at the prospect. I'm a little keener on finishing off (and developing my old) 120 rolls, since even my "poor man's medium format" Pentax 645 gives Velvia transparencies that are nice to look at. When my DSLR was a D700, getting 17MP out of a medium format scan was a useful prospect; now I have a 36MP sensor, not so much. I don't think I saw a film shot at last year's Wildlife Photographer of the Year (I could be wrong); in recent years I have seen 35mm film used, and at presentation size it's clearly lacking the microcontrast of the digital shots, even from older DSLRs. The last exhibition I saw had shots from compact cameras and a GoPro - they're the new "convenient". A while back there were large format shots entered too, but not so much now. Not that I've seen this year's yet.

 

Amazing shots have been captured on 135 film, for many reasons - convenience not the least. There are much more important aspects to a shot than the quality of the medium - something I show every time I produce something mediocre with all the money I've spent on NAS. But 135 was only ever a cheap way to get film by repurposing cinema stock, it was never designed for ultimate quality.

 

If we were going to define everything in terms of a specific format, I'd really rather we went the whole hog and just defined the field of view in terms of degrees. I can draw a little diagram and do some trigonometry, but trying to explain to a photographic novice (who may well never have seen a film camera, these days) the relationship between view and focal length is a pain.

In the beginning (of digital) there were only DX or smaller sensors, and there were no DX lenses, only lenses used for film.They fit a DX camera, but due to cropping, had the field of view of a longer lens. Would you have these legacy lenses labeled twice, once for film and once for the cropping factor, or can a reasonably intelligent adult multiply by 1.5? As with any endeavor, photographers quickly adapted to cropping sensors, and simply reached for the lens which would do what they needed, without pondering over the conversion factor.

 

That custom has prevailed for nearly 20 years, and only lenses sensors with unfamiliar dimensions are labeled as "equivalent", and often with the true focal length somewhere else (e.g., on the front bezel).

The intelligent thing would be for people to stop trying to teach novices in terms of "equivalent", and just accept that if you've got a DX camera, this is what (e.g.) a 35mm lens looks like on it. Sure, you can do the trigonometry, but everyone surely just gets used to what the field of view of a given lens on their preferred format looks like. It's only confusing because novices get taught by people who are used to 135 film who spend their time foisting their need to do a calculation on the novices.

 

It's perhaps fairer with a compact camera for which the sensor size is not obvious. But for an SLR, I think novices have "equivalence" forced on them earlier than they need to have. We (and quite possibly I, since it's a topic I keep spouting essays on) are probably fairly guilty of it on this forum.

Andy, Ed - you both amaze me. I was trying to learn, not teach. For me, with a photographic history going back to the '50's, the equivalence factor is a useful benchmark. :rolleyes:

Perhaps from a little different perspective: An FX lens of whatever focal length casts an image size designed to cover an FX sensor (or a 35mm film frame) at the listed focal length. A DX lens of the same focal length casts an image in which the subjects subtend exactly the same angles (their the same size on the sensor), but the size of the image circle is only big enough to cover a DX-sized sensor. Hence, the appearance of greater focal length, particularly when one compares images on FX and DX sensors of similar overall resolution (such as the 24 Mp sensor in my D7100 versus the 24 Mp sensor in my friend's D750). This is also why an FX lens on a DX body only gives the same image as the DX lens of equal focal length. There is simply a large portion of the image circle that extends beyond the edges of the DX sensor. The projected image of a models face covers exactly the same net sensor area on both sensors, but only occupies a fraction of the total sensor area on the larger, FX sensor. Does that help or make any sense?

 

Sandy, heads up! Our storm is headed your way. It dropped 9 inches of snow on us today, with more coming tonight. I expect you'll see some tomorrow.

Sandy, heads up! Our storm is headed your way. I

We've got nearly 2' right now - so far, just another 2 wks of cold forecast. Thanks for the warning - will check the weather before I shut down.

Sandy: Sorry, didn't meant to sound critical. Having got my head around what lenses look like on 35mm (though I started on Canon 1.6x crop), equivalence helps me to. I'm just not sure we should impose it on the next generation until they're actually trying to compare formats!

Well, when it comes to standards being accurate and universal.... xkcd: Standards

Already on my wall, Wouter. :-)

Just to add, how do you describe a field of view to someone who is maybe a photo novice (the people who need clear information the most)? I have found using the actual focal length just to confuse them - as they don't have a point of reference. Saying 'like 18mm on full frame' is much easier for them to grasp usually - unless they are up with different crops (which is easy once you know). I was chatting today, advising someone on a lens for their camera and said you could do with a 55-200mm (on D3000) but they were left confused still 'is that wide angle or normal' - as 50mm is still ingrained as 'our eyes see it'. I think we do need a standard, and 35mm format has proved easy to grasp.

I think my question is whether those of us with more equipment experience should be doing the conversion, or whether we should force it on a novice.

 

Before someone has a camera, you can go a long way with "very wide", "normal", "long", etc. Once they have a DSLR, if they have (say) an 18-55 and want a portrait lens, I think it's reasonably for us to say "on your camera, the traditional portrait lengths are between about 55 and 85mm". Often, we say "well, portrait lenses used to be considered to be 85-135mm on full frame, so in your case, you divide that by 1.5, and..." - which is information that someone with their first DSLR doesn't need to know. I'm very happy to explain "equivalence" with whatever sensor format, and if they're starting with a compact camera with focal lengths described in 35mm terms then it may be unavoidable, I just don't want to force new shooters to think in terms of a format they're never actually going to use just out of convention. They have enough stuff to learn. (And if we talk "equivalence", we have to start talking about equivalent aperture, equivalent sensor-level ISO, and other stuff that gets a bit tenuous and unnecessary.)

 

When I was learning, I asked how focal length related to field of view. You absolutely can say that the field of view is what you get if you hold up a 35mm slide frame (give or take slight cropping) at the focal length distance from your eye, but that's effectively very impractical (especially allowing for the aperture of the eye), and you may as well demonstrate equivalence by multiplying everything by ten (a 36cm x 24cm frame held 1m from you gives you the full frame field of view of a 100mm lens). Is this worth it? Well, it gets you out of explaining why a 36x24mm frame is called "35mm" (or why the 4/3 sensor isn't actually that size).

 

I'd love to describe everything in terms of angles of view, but in practice I'm not sure it helps.

Here is a tool which easily solves the problem - for anyone who can use a computer.

Nikon | Imaging Products | NIKKOR Lens Simulator

True, Sandy (and a useful link). Although only for Nikon formats (and not the optional crops or true APS bodies). I did once take a 14mm shot and put frame lines on it to show my sister how much you'd see with different focal lengths (she was camera shopping at the time).

 

I suspect there are tools out there that I've not bothered to touch which can handle other formats (Canon's 1.6x and 1.3x crops, the additional 1.3x crop that some Nikon DX bodies offer, the 1.2x crop on Nikon FX bodies, 4/3, Sigma sensors, larger formats, Pentax Q...) - it's not too difficult to automate such a thing if needed. You can get people used to the appearance of a given focal length, but I've certainly had the problem of "yes, but what does it mean?"

 

I wonder if there's a market in using halves of old rail view cameras with no lens holder in the front standard? If you had a chin on a rail and a (say) 7"x5" standard on the rail, the field of view you see through it is about that you get from a full frame body with a lens of 1/5 the focal length on it. (I.e. with the standard at 25cm down the rail, you get about a 50mm lens's field of view.) Just mentioning it in case any photographic educators out there have a broken studio camera that they're willing to let their students play with - buying a dedicated studio camera just to learn what a given focal length looks like isn't really a valid proposition for an individual. :-)