Same Focal length different lenses: If I were using the same camera with the same settings and 3 different lenses. Say the 24 to 105 the 18 to 300 and the 18 to 400. And don't hold me...

dyximan

If I were using the same camera with the same settings and 3 different lenses. Say the 24 to 105 the 18 to 300 and the 18 to 400. And don't hold me to the exact numbers you know what I mean. If all were set to the 100 focal length would the pictures be identical in say depth of field bokeh etc, not necessarily IQ, i know no one manufacturer manufactures all 3 lenses, but for the less snarky, intelligent ones you know what I'm talking about.

User ID

Yes, alike.

Someone will prolly say the bokeh will vary.
It would vary in "texture" due to differing
optical designs, but it will not vary in terms
of amount, which would be the same thing
as saying the "degree of defocus" is alike,
and that would be the same as saying that
the depth of field is alike. You might say the
"texture" of bokeh is included under "IQ".

imagemeister Loc: mid east Florida

dyximan wrote:

If I were using the same camera with the same settings and 3 different lenses. Say the 24 to 105 the 18 to 300 and the 18 to 400. And don't hold me to the exact numbers you know what I mean. If all were set to the 100 focal length would the pictures be identical in say depth of field bokeh etc, not necessarily IQ, i know no one manufacturer manufactures all 3 lenses, but for the less snarky, intelligent ones you know what I'm talking about.

There could be a SLIGHT difference due to exact optical designs - and the number of blades in the diaphram if stopping down. There could also be a slight difference in FOV depending on the closeness of focus.
.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

dyximan wrote:

If I were using the same camera with the same settings and 3 different lenses. Say the 24 to 105 the 18 to 300 and the 18 to 400. And don't hold me to the exact numbers you know what I mean. If all were set to the 100 focal length would the pictures be identical in say depth of field bokeh etc, not necessarily IQ, i know no one manufacturer manufactures all 3 lenses, but for the less snarky, intelligent ones you know what I'm talking about.

Mostly correct. Bokeh will be different at the same distance, and within a single lens, it can be different depending on the distance to subject, and distance to background. If you are at or near the minimum focus distance, internal focus lenses (nearly all lenses in production are IF) will shorten focal lengths. For instance, a Nikon 70-200 F2.8 VR II at 200mm will only show a field of view equivalent to around 135mm. The 28-300 is even worse, barely making a 120mm field of view at the 300mm setting. If the focal length is the same (actually, the magnification needs to be the same), the DoF will be the same as long as the focus distance and aperture are the same.

CO

Everybody has given great answers already. There's one difference I can think of and that is distortion. The three lenses will probably exhibit slightly different amounts barrel and pincushion distortion. There can also be the more complex mustache distortion. That's not exactly what you were asking about but something to consider if you're purchasing a new lens.

BebuLamar

You could have the same differences when compare 3 different 100mm lenses.

Scruples Loc: Brooklyn, New York

Different lenses will achieve different results. With that being written, using comparison photographs you will note these slight differences in the exposures and the exposure triangle. This is dependent on the internal elements set up which has taken a lens manufacturer years to perfect. Each lens was specifically designed for a specific body and the overall use will be different. Each of the lenses you have mentioned will achieve an overall "feel" of the photograph. Sure you can put a lens designed for a Canon EOS Rebel 2000 on a Canon 5D Mark II, but the lens may not achieve the intended results. Now the photographer's eye and brain come into play. You may not like the loss in the field of vision in this one but you may like the clarity and resolution of that one. Sometimes it can be a cr.&.pshoot. It is good to experiment especially in this gentle craft. You must remember that you are the photographer/artist. Your final photograph should garner accolades and not critique.

Happy Shooting!

dyximan

I want to thank all of you for your insightful Replies

Silverrails

dyximan wrote:

If I were using the same camera with the same settings and 3 different lenses. Say the 24 to 105 the 18 to 300 and the 18 to 400. And don't hold me to the exact numbers you know what I mean. If all were set to the 100 focal length would the pictures be identical in say depth of field bokeh etc, not necessarily IQ, i know no one manufacturer manufactures all 3 lenses, but for the less snarky, intelligent ones you know what I'm talking about.

My understanding is all these examples of Zoom lens, set at 100mm have the same Depth of Field.
If I understood correctly, my answer would be, it would depend on the "Aperture range" on each of the individual particular lens. Are they all the same or different?
Now, if I misunderstood your question, I am sorry and I know there are other UHH member here that may have better answer to your question.

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

dyximan wrote:

If I were using the same camera with the same settings and 3 different lenses. Say the 24 to 105 the 18 to 300 and the 18 to 400. And don't hold me to the exact numbers you know what I mean. If all were set to the 100 focal length would the pictures be identical in say depth of field bokeh etc, not necessarily IQ, i know no one manufacturer manufactures all 3 lenses, but for the less snarky, intelligent ones you know what I'm talking about.

No, they would not all have the same bokeh at 100 mm, slight differences are always apparent, and NO, the pictures would not all be identical as different lenses let in light differently through various number of internal lens elements, and, color and contrast may also vary. And NO, they would not all have the same depth of field unless they were all set to the same f stop, and even then, a discriminating eye may see a difference.

jerryc41 Loc: Catskill Mts of NY

I've tried something like this, and 100mm is not 100mm. That focal length is derived from a formula based on the lens. It's not like every ruler indicating the same length for three inches.

Architect1776 Loc: In my mind

Gene51 wrote:

Mostly correct. Bokeh will be different at the sam... (show quote)

george19

There’s a chart in the back of most aeronautical textbooks showing bank angle, airspeed, turn rate, and turn radius. Assuming no altitude loss, it doesn’t matter what kind of airplane you are flying...plug in any two numbers and the other two will fall out. For the snarky among you, bank angle and g loading can be treated identically. The point is, it’s physics.

So too, for given focal length, focus distance, and aperture, depth of field will be the same.

As others have noted, lens design may affect IQ, distortions, and other effects, but the above 4 parameters are physically tied to each other. Oh yeah, there’s an app for that.

camerapapi Loc: Miami, Fl.

Yes, focal length and apertures will be alike.

fetzler Loc: North West PA

There is good information above. In principal, the images should be the same. Lens distortion and the number of blades in the diaphragm might cause subtle differences. You may also observe differences in the exposure due to the light transmission. Lenses absorb some light. Cine lenses are marked with T stops and not f stops. T stops are corrected for light transmission. Two lenses with t 4 will give identical exposures those f 4 may not.